UpDeep surface geochemical reference material banktupa.gtk.fi/raportti/arkisto/26_2020.pdf · UpDeep surface geochemical reference material bank Abstract Quality assurance and quality

Geological Survey of Finland

Environmental Solutions Rovaniemi 25.5.2020 26/2020

Geologian tutkimuskeskus | Geologiska forskningscentralen | Geological Survey of Finland

Espoo Kokkola Kuopio Loppi Outokumpu Rovaniemi

www.gtk.fi Puh/Tel +358 29 503 0000 Y-tunnus / FO-nummer / Business ID: 0244680-7

UpDeep surface geochemical reference material bank

Maarit Middleton, Anne Taivalkoski, Pertti Sarala, Antti Taskinen, Tero Korhonen, Jens Rönnqvist, Dominika Mikšová

Geological Survey of Finland UpDeep surface geochemical reference material bank 25.5.2020

Geologian tutkimuskeskus | Geologiska forskningscentralen | Geological Survey of Finland

GEOLOGICAL SURVEY OF FINLAND DOCUMENTATION PAGE

25.5.2020 / GTK/773/03.01/2016

Authors

Maarit Middleton, Anne Taivalkoski, Pertti Sarala, Antti Taskinen, Tero Korhonen, Jens Rönnqvist, Dominika Mikšová

Type of report

GTK Open File Work Report

Commission by

EIT Raw Materials

Title of report

UpDeep surface geochemical reference material bank

Abstract

Quality assurance and quality control (QAQC) is a standard practice in evaluating the uncertainties in geochemical assay data. In surface geochemical mineral exploration, weak leach/partial extractions applied on soils and biogeochemical extraction techniques on plants are applied in grassroots and greenfield stages to guide the exploration process. The level of uncertainty in elemental assays for these sample materials is important information for the users to build confidence in the data they are dealing with, because the concentration levels in such soil and plant geochemical data sets may be low. In exploration, geologists and geochemists, as customers of analytical laboratories, need to run quality control procedures externally. To quantify the laboratory accuracy and laboratory precision, and to observe trends or blockiness in the analysis data, reference samples are distributed amongst the regular samples in the assay sequence before the samples are sent to a laboratory.

This report concerns the production of geochemical reference material (RM) samples for the establishment of a reference material sample bank. The procedures were tailored for partial extractions of organic (Ah horizon) and mineral soil (B horizon) under moist field conditions and laboratory dry-sieved conditions, as well as for ashed and dry-milled biogeochemical samples of conifers (Scots pine, Norway spruce, common juniper) in the laboratory. Sampling was conducted over two known Au prospects in Central Lapland. Samples were sent to 1–3 commercial geochemical laboratories for ‘round-robin’ analytical testing. The homogeneity in terms of relative standard deviation (RSD%) was categorised into good (RSD% ≤ 5), medium (RSD% = 5–15) or poor homogeneity (RSD% > 15) for each element.

RMs for the soil organic Ah horizon had medium homogeneity for the two analytical methods applied: modified aqua regia and sodium pyrophosphate. Differences in the results were observed between the homogenization methods (field vs. laboratory) of the B horizon RMs, although the degree of homogenisation was at a good level overall. For the sodium pyrophosphate leached RMs, laboratory-homogenized samples had a slightly better level of homogeneity than field-homogenized samples. For the modified aqua regia digested samples, field-homogenized sample samples turned more homogenous than the laboratory- homogenized samples. Therefore, field


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homogenization is adequate for mixing of the sampling material. For the plant RMs, the optimal homogenization time was found to be 15 min for ashed samples and 60 min for dry-milled samples. Overall, the ashed biogeochemical RMs contained a greater number of elements above the lower detection limit (>LDL) and they were more homogeneous than the dry-milled RMs, whose homogeneity varied considerably according to the element.

Concentrations of gold pathfinder elements such as B, Co, Cu, Fe, Mo, Pb and Zn were well above the LDL in the RMs, and both homogeneity and laboratory precision were good. This was true for all sampled plant materials analysed as ashed and dry-milled materials in all laboratories. Concentrations of Ag, As and Sb were mostly above the LDL, but their RSD values varied according to the material and the pre-treatment and analysis technique.

The RM production procedures presented in this report can be applied in the production of reference material for soils and plants from many environments and using various analytical procedures. The RMs produced as described in this report do not fulfil the quality requirements for certified RMs. However, they can be produced and used cost-efficiently to monitor laboratory quality externally for soil and plant samples and mineralisation types relevant to a particular study when off-the-self RMs are not available for the target element, its concentration ranges and the sample matrix. The RM samples produced into the demonstration RM bank are most suitable for Au and REE exploration, but may also be applied in exploration for other commodities.

Keywords

quality control, quality assurance, reference material, surface geochemical exploration, soil, partial extraction, biogeochemistry

Geographical area

Finland, Europe

Report serial

GTK Open File Work Report Archive code

26/2020

Total pages

30 p., 5 appendices Language

English Price

Confidentiality

Public

Unit and section

Environmental Solutions Project code

UpDeep

Signature/name

Maarit Middleton

Signature/name

Anne Taivalkoski


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Contents

Documentation page

1 Introduction 5

2 UpDeep SRM material collection and preparation 9

2.1 Soil sampling and preparation 9

2.2 Plant sampling and preparation 14

3 Content and quality of the UpDeep reference materials 16

3.1 Soil reference materials 18

3.2 Plant reference materials 21

4 Storage and delivery 23

4.1 Soil reference materials 23

4.2 Plant reference materials 24

5 Recommendations for the production of soil and plant reference materials 24

5.1 General recommendations for producing surface geochemical reference materials 24

5.2 Recommendations for producing soil reference materials 26

5.3 Recommendations for producing plant reference materials 26

6 Literature references 27

7 Acknowledgements 30

8 Appendices 30


5

1 INTRODUCTION

Chemical analyses of plants and soils for surface geochemical mineral exploration are conducted by specialized research and commercial laboratories as a standard practice. However, their applicability in mineral exploration is highly dependent on the data quality. Similarly to any geochemical survey, quality management plays an important role in surface geochemical exploration, which, in the context of this report, is considered as mineral exploration based on the partial extraction of soil horizon and plant biogeochemical samples. Most laboratories are accredited following standardised quality control procedures for internally observing the processes of sample preparation and analysis. Nevertheless, anyone acquiring geochemical samples should run external quality control procedures to gain confidence in the quality of the laboratory data and the repeatability of sampling. There are several ways to quantify uncertainties in a geochemical exploration project. Samples can be randomized prior to analysis to observe major trends, breaks, blockiness and faulty outliers in laboratory data, field precision can be quantified by taking duplicate and/or replicate samples, and laboratory precision can be quantified by requesting laboratory duplicates or replicates at any stage of sample pre-processing or analysis. The precision and accuracy of laboratory analysis, analytical trends and blockiness are often monitored by inserting reference materials (RMs) into an analytical sequence prior to sending the routine samples to the laboratory (e.g., Reimann et al. 2008). This report concerns the production of uncertified RMs to be used in surface geochemical mineral exploration based on soils and plants.

Standard reference materials (SRMs) are one type of reference material utilised to evaluate the quality of laboratory analysis for geochemical sampling media, including surface geochemical materials (e.g., Gopalakrishnan 2005; Mackey et al. 2010). This report does not aim at describing the production of certified reference materials (CRMs), which by definition should follow the ISO Guides (30, 31, 35, 17034), IAEA (2003), European Commission (2017) or CANMET (2017), and should be produced in an ISO standardised (Guide 34) laboratory. Thus, CRMs have significantly higher quality standards than the RMs described in this report. Because the preparation of SRMs is less rigorous, they are more affordable and can thus be inserted more frequently (10–20 per cent) into an analytical batch (Kalra 1998, Ihnat et al. 1998a, b, Dunn 2007, Rawlins et al. 2012). For plants and soils, ‘round robin’ tests (i.e., analysing a number of subsamples) often cannot be performed in several laboratories, as required by ISO standardization,


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because analytical work may be patented or analytical procedures may vary from one laboratory to another. Thus, these surface geochemical sampling media could never meet the criteria for certified values. Therefore, only indicative or information values can be presented for SRMs. The RM types described in this report are variously referred to in the literature as standard reference materials (SRMs), geochemical reference materials, control reference materials, project reference materials (PRMs) and in-house/site/study standards (see e.g., Bloom 2002, Geboy and Eagle 2011, Okai 2016).

A common purpose when inserting SRMs into an analytical batch is to externally monitor the analytical accuracy by comparing the SRM concentrations analysed together with a client’s routine samples with the pre-analysed concentrations. The difference is quantified as bias. Statistical values (e.g., bias-%) and control charts (e.g., X-charts) are used to monitor laboratory accuracy. When SRM samples are inserted together with the routine samples into the analysis sequence just before supplying them to the laboratory, the accuracy captured is termed laboratory accuracy. The quantified laboratory accuracy thus accumulates uncertainties caused by all stages of laboratory work, including possible drying, milling, sieving, digestion and analysis. SRMs inserted just prior to sending samples to a laboratory cannot be used to monitor the quality of sampling or sample preparation. However, if this is of interest, SRMs could be also inserted in any stage of sample handling. RMs produced at the field location, handled and transported with the routine samples, would include uncertainties caused by preparation. Thus, this type of material could be used for checking the whole sample analysis procedure from sampling and preparation to chemical analysis. The idea of field-produced RMs is presented in this report alongside laboratory-produced RMs.

It should be noted, however, that absolute accuracy of laboratory analysis is not a necessity in surface geochemical mineral exploration, as the purpose is to compare relative differences in sample concentrations within a sample batch sent to a laboratory for exactly the same analysis procedure conducted during one period of time. Data may be still usable even though they contain bias. Accuracy becomes important if samples are supplied to a laboratory in several batches and if different laboratories or analytical methods are used. SRMs may then be used for the levelling of concentrations between different data batches.


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A more meaningful aspect of uncertainty monitored with SRMs in the context of surface geochemical mineral exploration is laboratory precision. SRMs are homogenized in the preparation phase such that every time a subsample is analysed, the concentrations should fall within an acceptable range of variance, commonly quantified as the relative standard deviation (RSD). If laboratory precision is poor in relation to the concentration range of an analyte, false positives could be interpreted in the data.

Additionally, if SRMs are frequently inserted, they can be used to reveal trends, level differences, breaks and blockiness in the laboratory-produced data. Visual interpretation of X-charts may reveal these. Commonly, about 5% of all samples are SRMs and they are evenly distributed through the analysis sequence. A sufficient number and even distribution of SRMs ensures that possible trends in the laboratory analysis are captured.

Two ways to prepare samples of reference materials are presented in this report. Firstly, a procedure to prepare and homogenize soil samples under field conditions is described. In this case, the samples can be blindly inserted into the analysis sequence in the same moisture state as the routine samples. Samples of this type cannot be used for accuracy monitoring, but are well suited to precision monitoring if they are homogeneous enough. However, field preparation of plant SRMs is not applicable, because tissue samples are in a macro-state and homogenization would thus be challenging or impossible.

Secondly, a routine to produce samples in the laboratory is described. These samples are usually dried and sieved/milled/ashed prior to homogenization to ensure that the SRM is homogeneous and to enable a long storage time. These pre-prepared SRMs can be blindly submitted to the analytical laboratory only if the routine samples are pre-treated in the same way as the SRMs, e.g., milled to the same grain size, or ashed and supplied in similar bags and with similar coding to the routine samples. This, however, requires work from the party carrying out the sample preparation.

Based on literature and Internet searches, SRMs of different soil horizons and different plant tissues for weak/selective leaches are not easily or at all available on the European market. Rising environmental issues are becoming increasingly important in exploration


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activities, and the demand for ultra-low-impact methods in mineral exploration is growing. This will also increase the demand for suitable material for quality control purposes. The lack of such RMs initiated the specification and construction of a bank of reference materials for different plant tissue and soil horizon samples. The availability of such an SRM bank would be beneficial for small surface geochemical projects (less than a couple hundred samples) in which the production of project-specific RMs would not be time- or cost-efficient.

This work was accomplished in the UpDeep project, whose aim was to establish a procedure for the production of reference materials for external quality monitoring of weak/selective soil leach and plant tissue geochemical data. The aim was not to create a complete reference bank but to demonstrate with a small number of samples and with a few sample materials (analysed with a limited number of analytical methods in a few laboratories) how

the reference sample bank could be constructed. The secondary goal was to optimise the homogenisation time for plant SRM production.

This report describes how biogeochemical SRMs can be produced for mineral exploration focused on Au and rare earth elements. In the UpDeep feasibility study, the target commodity element for the developed surface geochemical consulting business was defined to be Au. Thus, the samples available in the current UpDeep SRM bank are most suitable for monitoring the accuracy and precision of samples taken in similar geological environments, because the crucial elements occur in similar concentration ranges and are within the sensitivity range of the analytical method. This, however, does not prevent the use of these samples in surface geochemical exploration projects focused on other types of deposits. The users simply need to verify that the elements of interest are within the sensitivity range of the method. However, these SRM production procedures can be followed for the production of SRMs for any commodity element/deposit type and their pathfinder elements, and also for other types of soil and plant sample materials.

The selected sample materials for the constructed UpDeep SRM bank were four different plant tissues and two types of soil samples. The analysis was performed in three laboratories, which differed in their partial extraction analytics and versions of the modified aqua regia digestion, applying a variety of sample pre-treatment methods, including different particle sizes. Thus, the reference concentrations presented here


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should be considered specific to the laboratory, sample preparation technique and sample analytics if the monitoring of absolute accuracy and slight differences in precision are of interest. This demonstration study presents the basis for constructing a reference sample bank for weak soil leach and biogeochemical methods to serve environmentally friendly mineral exploration.

2 UPDEEP SRM MATERIAL COLLECTION AND PREPARATION

Sampling for the UpDeep surface geochemical reference material bank was carried out in two target areas in northern Finland. The sampled sites had an undisturbed soil cover and no contamination sources were located close by. The Mäkärä site (sampled 12–13 June 2017) is located in northern Sodankylä and the Tiira site (sampled 24–25 June 2017) in northern Kittilä, Finland. The Mäkärä target is a Au–REE-bearing quartz hematite vein (permit owned in 2017 by the Geological Survey of Finland; Sarapää and Sarala 2013) and the Tiira site is an exploration target for Au (permit owned by Agnico-Eagle Finland Ltd.; Härkönen et al. 2000, Agnico-Eagle Finland Ltd. 2015, Molnár et al. 2018, Geological Survey of Finland 2020). Table 1 summarizes the soil materials collected from different soil horizons and plant tissue types for the UpDeep RM bank and the development of the SRM production procedures. The RM types produced from the sampled materials are also listed.

2.1 Soil sampling and preparation

Organic Ah horizon soil sample material

The existence of the Ah horizon, which is a well-decomposed dark organic layer immediately on top of mineral soil, was examined prior to sampling in the entire sampling area. The organic poorly decomposed root layer was first removed from an area of approximately 1 m2. The Ah material was gently scraped with a plastic scoop into a plastic tub from the contact of the mineral soil. The thicker roots and stones were removed. Since an adequate amount of the material could not be collected from one sampling location, the Ah material was collected from five to six different sampling locations within the Mäkärä site and the described sampling procedure was repeated at each location. The collected Ah material was stored in a large plastic bag.


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Table 1. Summary of collection sites, reference materials and their pre-treatments.

Location Sampled material

Reference material type Reference sample name

Soil geochemical SRMs

Mäkärä Ah-horizon Homogenized in the field, dried

UPDEEP_ORG_Ah1

Mäkärä B-horizon Homogenized in the field, dried

UPDEEP_MIN_B1

Homogenized in the field, natural moisture level

UPDEEP_MIN_B2*

Sieved and homogenized in the laboratory, dried

UPDEEP_MIN_B3

Plant biogeochemical SRMs

Mäkärä Common juniper foliage

Ashed needles UPDEEP_JUN_NEED_ASH

Ashed twigs UPDEEP_JUN_TWIG_ASH

Mäkärä Scots pine bark

Ashed bark UPDEEP_PINE_BARK_ASH**

Tiira Norway spruce bark

Dry powdered bark (<1 mm) UPDEEP_SPRU_BARK_DRY

Tiira Norway spruce twigs and needles

Dry powdered needles (<1 mm)

UPDEEP_SPRU_NEED_DRY

Dry powdered twigs (<1 mm)

UPDEEP_SPRU_TWIG_DRY

*For ionic leach samples. Only used in preparation testing; not included in the UpDeep reference material bank because the material ran out.

**Only used in preparation testing; not included in the UpDeep reference material bank because the material ran out.


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After collection, the Ah material was homogenized in the field: the material was pooled into a clean plastic tub and the material was stirred with a sandblasted shovel for about 10 minutes. Subsamples of 120 g of the homogenized material were placed in plastic zip-lock bags. In the laboratory, the zip-lock bags were opened and the subsamples were dried at 40 °C for two days. The adequacy of the drying time was tested by weighing the sample bags twice a day (Fig. 1). After drying, the samples were kept in a dry place at room temperature.

Figure 1. Pre-processing flow chart for organic Ah horizon material and sample IDs.

Eight samples of the reference material UPDEEP_ORG_Ah1 were sent to two laboratories for analysis: ALS (Vancouver, Canada, through Sodankylä, Finland) and Bureau Veritas Commodities Canada Ltd (BV Acmelabs, Vancouver, Canada). The samples were dried at 60 °C in BV Acmelabs. Before analysis, the samples were sieved to <180 µm in ALS and to <80 µm in BV Acmelabs.

The following analytical methods were selected for the UPDEEP_ORG_Ah1 samples:

weak acid leach (super trace modified aqua regia 1:1 HNO3:HCl, ICP-MS analysis,

method code ME-MS41W-REE, ALS);


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modified aqua regia digestion (1:1:1 HNO3:HCl:H2O, ICP-MS analysis, method

code AQ250, BV Acmelabs);

partial leach with 0.1 M sodium pyrophosphate (method code: LH103, ICP-MS

analysis, method code: LH103, BV Acmelabs).

Mineral B horizon soil sample material

Mineral soil samples were collected from the B horizon at the same sampling locations as the Ah-horizon samples. After collecting the Ah material, the test pits were deepened for collection of the B-horizon material. As the B-horizon material was easier to collect, it was only acquired from four sampling locations. The material was simply scraped with a plastic scoop into a plastic tub and stored in a large plastic bag.

The collected mineral soil material was homogenized in the field: the material was pooled into a clean plastic tub and was stirred with a sandblasted shovel for about 5 minutes. The homogenized material was split in two parts (Fig. 2). The first half of the material was divided between plastic zip-lock bags, each with a weight of 125 g. The subsamples were dried in the laboratory at 40 °C for one day (Fig. 2). Ten subsamples of UpDeep_MIN_B1 were sent for laboratory analysis.

Figure 2. Pre-processing flow chart for mineral B-horizon material homogenized in the field. IDs of the sample aliquots sent for analysis are given.


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The other half of the bulk sample with a natural moisture level was packed into a plastic bag. The bulk material was sent to the mineral processing laboratory of GTK Mintec (Mineral Processing and Materials Research Unit, Outokumpu, Finland). Ten subsamples were taken separately and stored in a fridge to await later delivery for ionic leach analysis (UpDeep_MIN_B2.1-10). The rest of the sample material was dried at 40 °C for one day, and after drying, all the lumps were ground and the material was homogenized and split into two. Half of the bulk sample was sieved to a size fraction of <180 µm, forming the reference material UpDeep_MIN_B3, and ten subsamples (UpDeep_MIN_B3.1-10) of 50 g each were taken to be sent to the laboratories (Fig. 3). The rest of the dried bulk sample material was stored at room temperature in a dry place. The other half of the homogenized material was stored as bulk sample material UpDeep_MIN_B4, and the quality of this material (Fig. 3) was not tested. This unsieved material could be used to create a new SRM in the future.

Figure 3. Pre-processing flow chart for mineral B-horizon material homogenized in GTK’s Mintec laboratory.

Ten field-homogenized dried subsamples (UpDeep_MIN_B1.1-10), ten subsamples with natural moisture levels (UpDeep_MIN_B2.1-10) and ten laboratory-homogenized subsamples (UpDeep_MIN_B3.1-10) were sent to ALS, where the field-homogenized subsamples (UpDeep_MIN_B2.1-10) were sieved to a size fraction of <180 µm.


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Three analytical methods at ALS were selected for mineral soil samples:

Ionic leachTM (ICP-MS analysis, method code ME-MS23) of samples with natural

moisture levels;

weak acid leach (super trace modified aqua regia 1:1 HNO3:HCl, ICP-MS analysis,

method code ME-MS41W-REE) for field-homogenized and laboratory-

homogenized samples;

sodium pyrophosphate leach (ICP-MS analysis, method code ME-MS07) for field-

homogenized and laboratory-homogenized samples.

2.2 Plant sampling and preparation

At the Mäkärä Au prospect, 4.2 kg of bark scales were collected from Scots pines, while at the Tiira Au prospect, 3.4 kg of bark scales were sampled from Norway spruces. The bulk bark samples were collected from tree trunks from a height of 0.5–2 m above the ground surface by scraping with a hardened steel paint scraper and allowing the bark dust and scales to fall onto a plastic pan that was held beneath. Concurrently, 53 kg of juniper foliage was collected at the Mäkärä site and 37.5 kg of Norway spruce foliage samples at the Tiira site. The foliage samples only included the tips of twigs with a length of ca. 20 cm and a twig diameter of less than 0.5 cm. All samples were transferred to breathable bags.

After sample collection, the breathable bags were hung in a well-aerated place until they were dried in an industrial oven at 40 oC for 48 hours. No further sample preparation steps were taken for Mäkärä Scots pine bark samples (UPDEEP_PINE_BARK) or for Tiira Norway spruce bark samples (UPDEEP_SPRU_BARK). The common juniper foliage samples from Mäkärä and Norway spruce foliage samples from Tiira were manually sorted such that the needles were separated from the twigs.

Biogeochemical sample preparation continued at the mineral processing laboratory of GTK Mintec in Outokumpu with milling of the dried biogeochemical materials using a


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cutting mill (Retsch SM 300), the rotor and the bottom sieves of which are made of heavy-metal-free steel. The dry powder reference materials were ground to a particle size of <0.5 mm. Samples to be ashed were ground to a particle size of <1 mm and delivered for ashing to Labtium Oy, Kuopio. The samples were ashed in porcelain crucibles at 475 ˚C for 48 hours at maximum.

Homogenization was performed by rotating the samples in a plastic container (3 litres) placed inside a rod mill. The rotating speed was set to ca. 20 rpm. In most cases, a 400-g aliquot of dried and milled material or a 70-g aliquot of ashed material was homogenized at a time.

The purpose was to test the effect of homogenization on the dry-milled and ashed SRMs, i.e. the time required to optimally homogenize the sample media was tested. The testing was performed with two sample media only: UPDEEP_PINE_BARK_ASH and UPDEEP_SPRU_TWIG_DRY (see Fig. 4 as an example of the homogenization procedure). Prior to homogenization, the sample material was placed on kraft paper on a flat surface and thoroughly mixed using a plastic scoop. Ten subsamples were taken from the bulk sample. After each homogenization period (15 minutes for ashed samples and 30 minutes for dry weight samples), another ten aliquots were taken from the homogenization container and packed into small envelopes (2.0–2.5 g of dry-milled material and 0.5–0.6 g of ashed material).

The optimal homogenization time was determined to be 60 min for dry-milled material and 15 min for ashed material by calculating the RSD% of the 10 aliquots taken after each homogenization period. The rest of the dry-milled and ashed SRMs were produced with these homogenisation times, assuming that the ashed common juniper needles and twigs and dry-milled Norway spruce would behave similarly when homogenized.

Two external SRMs produced by Colin Dunn Consulting Inc. were used to monitor the laboratory accuracy, precision and trends. Ashed black spruce needles (SRM: V8a) from a treetop survey in Manitoba, Canada, were used with the ashed Scots pine bark, and dried black spruce twigs (Picea mariana) from the vicinity of the former Rottenstone PGE–Ni open pit in northern Saskatchewan (SRM:P5)


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Figure 4. Flow chart for the preparation of UPDEEP_SPRU_TWIG_DRY samples for homogenization testing. Homogenization testing was also conducted similarly on ashed UPDEEP_PINE_BARK.

Four globally operating commercial laboratories were considered for the analytical work, but eventually, only three were chosen for round-robin testing for budgetary reasons (see Table 2). These are commercially operating accredited geochemical laboratories that provide geochemical analyses for mineral exploration purposes. All of these laboratories offer analysis of dry-milled and also ashed plant material. However, the analytical procedures differ between the laboratories. The comparison of the laboratories was based on the 2018 brochures/schedules available on their webpages. The analytical work for homogenization testing was only performed in one laboratory, ALS.

3 CONTENT AND QUALITY OF THE UPDEEP REFERENCE MATERIALS

The ‘off-the-shelf’ SRMs in the UpDeep reference material bank are summarised in Table 3. For each SRM type, the UpDeep reference material bank includes:

physical samples that can be shipped to the customer to be inserted with their

own routine samples in the quantity required by the customer;


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pre-analysed values for 8–10 subsamples of these UpDeep SRMs: all analysed

element concentrations from different laboratories are available in Appendix 2

and summarised in Appendices 4 and 5;

descriptive statistics and exploratory data analysis graphs for the pre-analysed

subsamples to evaluate the usefulness of the SRMs in one’s own project

(Appendices 2 and 3);

reports describing each UpDeep SRM (Appendix 3).

Since the purpose of our study was to generate surface geochemical SRMs for Au exploration, the focus was on the examination of pathfinder elements commonly related to orogenic, IOCG, VMS, epithermal, porphyry and Carlin-type Au deposits. These elements include Ag, As, B, Bi, Co, Cu, Hg, Mo, Pb, Sb, Se, Te, W and Zn (compiled from Pearson 1963; Sillitoe and Hedenquist 2003; Robb 2005; Emsbo et al. 2006; Dubé et al. 2007; Tooth et al. 2008; Goldfarb and Groves 2015). In addition, hydrothermal alteration systems related to Au mineralization have significant enrichment of K, Rb, Sn and S, and commonly also Th and U (Zhu et al. 2011; Patten et al. 2016). A high Fe concentration is also a significant indicator and is seen as a high abundance of magnetite in hydrothermal altered systems. The focus was also on the rare earth elements (REE), since the Mäkärä site has a range of REE elements (Sarapää and Sarala 2013). The quality of these elements is discussed in the following sections.

The homogeneity of the UpDeep SRMs can be evaluated based on the RSDs of the analysed 10 aliquots, which are summarized in Appendices 4 and 5. The RSD% values are classified into three categories: good homogeneity (RSD% ≤ 5), medium homogeneity (RSD% = 5–15) and poor homogeneity (RSD% > 15). All values can be considered as ‘information values’, because the UpDeep SRM bank cannot meet the requirements of any standard. Elements that were not analysed are indicated as ‘-’ and elements that had more than three values under the lower detection limit (<LDL) or above the upper detection limit (>UDL) are indicated as ‘NA’, because the RSD value could not be calculated. As the UpDeep RMs are not certified, even the good RSDs (<5%) can only be considered as indicative values.


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For all analytical results, the mean, median, standard deviation (SD), relative standard deviation percentage (RSD%) and median absolute deviation (MAD) values were calculated (Appendix 2).

Sets of results obtained from the same analytical laboratory using a different analytical method are treated independently, even though they were run on the same SRM type. The reason for this is that analytical procedures, including pre-treatment and digestion protocols, vary from one laboratory to another.

3.1 Soil reference materials

The Ah sample material was homogenized as a fresh bulk sample in the field and then dried in the laboratory. Subsamples resembled the routine samples collected during a sampling campaign for mineral exploration purposes. Three analytical datasets based on two different modified aqua regia leaches and one sodium pyrophosphate leach in two laboratories displayed similar concentration levels and variation for most of the elements. Both laboratories reported the analytical results of aqua regia leach at the ppm level (Al, Ca, Fe, K, Mg, Ti, Na, P and S at the per cent level). Comparison of the RSD values shows that the values were mostly between 5% and 15% for both extractions, indicating medium homogeneity. Compared to the results from ALS, there were more RSD values of <5% in the results produced by BV Acmelabs. The number of elements having more than three measurements that were <LDL was five in the ALS results and eleven in the BV Acmelabs results. In addition, most of the RSD values for the sodium pyrophosphate results were 5–15%, and ten elements had concentrations <LDL.

The mineral soil (B horizon) samples were analysed at ALS with three different methods. The difference between UpDeep_MIN_B1 and UpDeep_B3_MIN samples is that B1 samples were homogenized in the field, whereas B3 samples were homogenized and sieved in the laboratory. The purpose of the differing sample preparation was to estimate whether homogenization in the field was adequate for mixing of the sample material to produce sufficiently homogeneous subsamples. The sodium pyrophosphate results for samples homogenized in the GTK Mintec laboratory indicate that most of the RSD values were <5%, but in the results for field-homogenized samples, half of the RSD values were between 5 to 15%. The modified weak aqua regia results were the

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Table 2. The laboratories used, their laboratory codes and their explanations. Detection limits for each analytical package can be found in the laboratory schedules provided in the ‘order’ folders of each laboratory package in Appendix 1.

Laboratory Actlabs Actlabs ALS ALS ALS ALS ALS BV Acmelabs BV Acmelabs

Analytical package

2FSpecial 2E MEVEG41a ME-VEG41a_REE ME_HALO1a ME-VEG41 ME-VEG41-REE VG101-EXT-REE VG104-EXT-REE

Pretreatment at GTK Mintec

Dry-milled Ashed Ashed Ashed Ashed Dry-milled Dry-milled Dry-milled Ashed

Sample weight (g)

0.5 0.25 0.25 0.25 0.25 1 1 1 0.5

Leach Aqua regia at 95 °C for

2 hours

Aqua regia at

95 °C for 2 hours

Digested in 75% aqua

regia using a digestion

block operating at

115 °C

Digested in 75% aqua regia using a

digestion block operating at 115

°C

Ashed samples

leached with hot

deionized water, then

centrifuged to remove

solid

Cold digested with nitric acid for 8 hours before

being transferred to hot block for 15 minutes at

85 °C followed by 2 hours at 115 °C

Pb-OG46: Aqua regia digestion and ICP or AAS

finish.

Cold digested with nitric acid for 8

hours before being transferred to hot

block for 15 minutes at 85 °C

followed by 2 hours at 115 °C

HNO3 then aqua regia

Modified aqua regia digestion 1:1:1 HNO3:HCl:H2O

Instrumentation

Finnegan Mat

Element 2 High

Resolution ICP/MS

(HR-ICP/MS)

Perk in Elmer Sciex ELAN 6000,

6100 or 9000

ICP/MS

Agilent 725ES

(ICPOES) and Agilent 7900

(ICP-MS) corrected for

spectral interference

s

Agilent 725-ES (ICP-OES) and

Agilent 7900 (ICP-MS) corrected for

spectral interferences

Inductively Coupled

Plasma Mass Spectrometry (ICP-MS)

and Ion Chromatogra

phy (IC

Agilent 725-ES (ICP-OES) and Agilent 7900 (ICP-

MS) corrected for spectral interferences

Agilent 725-ES (ICP-OES) and Agilent

7900 (ICP-MS) corrected for

spectral interferences

ICP-MS/ICP-OES ICP-MS/ICP-OES

# of elements 61 63 53 12 4 53 8 64 63

Geological Survey of Finland UpDeep surface geochemical reference material 20.5.2020

21

Table 3. The UpDeep reference material types available in the UpDeep reference material bank.

Soil geochemical SRMs

Mineral B horizon

Field homogenization, drying at 40 °C, sieving <180 µm, sample weight 120 g

UpDeep_MIN_B1

Mineral B horizon

Drying at 40 °C, laboratory homogenization, sieving <180 µm, sample weight 50 g

UpDeep_MIN_B3

Organic Ah horizon

Field homogenization, drying at 60 °C UpDeep_ORG_Ah

Plant biogeochemical SRMs

Norway spruce needles

Drying at 40 °C, milled <0.5 mm, laboratory homogenization, sold by weight


Norway spruce twigs



Norway spruce bark


UPDEEP_SPRU_BARK_DRY

Common juniper needles

Drying at 40 °C, milled <1 mm, ashing at 475 °C, laboratory homogenization, sold by weight

UPDEEP_JUN_NEED_ASH

Common juniper twigs

Drying at 40 °C, milled <1 mm, ashing at 475 °C, laboratory homogenization, sold by weight

UPDEEP_JUN_TWIG_ASH

opposite: almost half of the RSD values of the field-homogenized samples were <5%, but half of the laboratory-homogenized samples had RSD values of 5–15%. This indicates that field homogenization may be adequate for the production of soil Ah and B horizon SRMs.

Analysis of the UpDeep_MIN_B2 subsamples was conducted on samples with natural moisture levels. The RSD values indicate good homogenization, as 26 elements had RSD < 5% and 27 elements had an RSD of 5–15%. No report of UpDeep_MIN_B2 is presented here, because after the homogenization testing, not enough material was left to be distributed to future customers.

3.2 Plant reference materials

Ashed SRMs had a greater number of elements >LDL and they were more homogeneous than dry-milled SRMs (see Appendices 2 and 5). The production and analysis of the dry-milled SRMs was more


22

difficult because, besides being in nanoparticles, elements also biomineralize within the plant tissue (Dunn 2007). The degree of homogeneity for dry-milled samples may be improved by reducing the grain size to <<0.5 mm. No report of UPDEEP_PINE_BARK_ASH is presented here, because after the homogenization testing, not enough material was left to be distributed to future customers.

The X-charts drawn for the external SRMs reveal systematic bias, i.e. differences in the concentration level between the pre-analysed samples and samples analysed with the UpDeep SRMs. Factors contributing to this bias are related to the leaching procedures, especially differences in the extraction strengths, acid ratios, temperatures and acid-sample exposure times, which are laboratory method-specific. This further confirms that the UpDeep SRMs are best used in a laboratory- and laboratory-code-specific manner if laboratory accuracy is to be monitored using them. However, if the intention is to monitor laboratory precision, drift, periodic concentration shifts, unusual breaks and outliers in analytical results, this is not an issue. In mineral exploration, the interest is not in the absolute accuracy of the analyses as much as the precision of the results.

The UpDeep SRMs UPDEEP_SPRU_TWIG_DRY, UPDEEP_SPRU_NEED_DRY, UPDEEP_JUN_TWIG_ASH and UPDEEP_JUN_NEED_ASH, UPDEEP_SPRU_BARK_DRY are acceptable as SRMs in terms of homogeneity. Gold pathfinder elements such as B, Co, Cu, Fe, Mo, Pb and Zn are well above the LDL and homogeneous, with good precision (see Appendices 2 and 5). This was true for all sampled plant materials analysed from ashed and dry-milled materials in all laboratories. Concentrations of Ag, As and Sb were mostly above the LDL, but their RSD values varied according to the material and the pre-treatment and analysis technique. Bismuth and Te were only above the LDL for a few sample materials, making it impossible to monitor the quality of the customer’s Bi and Te results with the UpDeep SRMs in the future. The results for two other common Au pathfinders, Hg and Se, indicate that monitoring analytical quality is only possible for dry-milled materials. Mercury is known to almost completely volatilize, whereas Se is known to partly volatilise (Dunn 2007). In contrast, W results were only above the LDL for ashed materials from the Mäkärä target.

Gold, being the most important element at both the Mäkärä and Tiira sites, was expected to be above the detection limit. The Au results of ALS and BV Acmelabs were mostly within the ICP sensitivity range. The RSD% was consistently >15%, which is expected considering the geochemically ‘nuggetty’ nature of Au. This causes heterogeneity in the analytical results, regardless of the sample pre-treatment. The Actlabs packages could not produce acceptable Au results at all, meaning that the results did not pass their internal quality control.

Rare earth elements were mostly over the LDL and their homogeneity was acceptable (5 < RSD% < 15) in the ashed data collected over the Mäkärä Au–REE prospect. However, in the dry-milled samples collected over the Tiira Au–prospect, they were commonly <LDL. Similarly to W, the sampling location may be the main factor causing this difference rather than the sample pre-treatment.


23

4 STORAGE AND DELIVERY

4.1 Soil reference materials

UpDeep_ORG_Ah1, UpDeep_MIN_B1 and UpDeep_MIN_B3 materials are maintained at room temperature in a dry place. UpDeep_ORG_Ah1 and UpDeep_MIN_B1 materials are delivered to customers as unsieved samples (weight of 120 g and 125 g, respectively, Fig. 5) and they need to be sieved to an adequate size fraction prior to analysis. UpDeep_MIN_B3 material is delivered in plastic zip-lock bags as a 50-g samples and is sieved to a particle size of <180 µm (Fig. 6). This material should be sieved prior to analysis if a finer particle size is used in analysis.

Ionic leachTM is required for the analysis of unsieved samples with natural moisture levels, which UpDeep_MIN_B2 samples represent. Soil material with natural moisture levels requires refrigeration or freezing for sample storage. RMs with natural moisture levels were not included in the UpDeep reference sample bank.

a

b

Figure 5. Sample bags of the dried, unsieved organic Ah horizon (UpDeep_ORG_Ah1) and mineral soil materials (UpDeep_MIN_B1) a) stored in a dry place and b) packed in zip-lock bags ready for delivery.


24

Figure 6. Sample bags of the dried, sieved mineral soil materials (UpDeep_MIN_B3). The small subsamples on the left were used in the laboratory analyses in the UpDeep project and the rest of the material was stored in one large plastic bag (on the right) for later use.

4.2 Plant reference materials

SRM subsamples can be delivered to a customer as a bulk sample or in individually packed envelopes of the desired weight. Figure 7 illustrates (a) the individually packaged samples and (b) bulk plant SRMs stored in 250-ml HDPE bottles ready to be sent to customers. The UpDeep biogeochemical SRMs are maintained in a dry storage room at room temperature. Glass marbles are placed in the HDPE bottles to allow shaking of the material prior to taking aliquots of the material. When an order is placed by a customer, an appropriate weight of the sample should be prepared according to the customer needs. For ashed materials, weights of 0.25 g or 0.5 g are commonly used, whereas 0.5 g, 1 g or 5 g weights are common for dry-milled plant materials. During weighing of the sample, at least 0.1 g of extra sample should always be included, because some material sticks to the inside of the envelope. On customer request, double-weight samples can be supplied to allow duplicate analysis of the material, e.g. as analytical duplicates or in case a reanalysis is requested by the customer. If the customer is preparing routine samples and wants to insert the SRMs as blind samples, customer-supplied envelopes and/or sticker tags can be used.

5 RECOMMENDATIONS FOR THE PRODUCTION OF SOIL AND PLANT REFERENCE MATERIALS

5.1 General recommendations for producing surface geochemical reference materials

In the following, general recommendations for the production of surface geochemical SRMs for partial soil leaches and plant tissues are provided.

Prior to sampling for RMs, landowner permissions should be applied for and obtained.


25

a

b

Figure 7. SRM samples a) in paper envelopes and b) in 250-mL HDPE bottles.

Sampling should take place on known exploration targets of the specific deposit type under

investigation.

When planning the sampling of soil reference materials, the selected area should contain

suitable concentration levels of the elements of interest. The analytical detection limits of the

commercially operating geochemical laboratories are still rather high for biogeochemical

analyses. Therefore, it is advisable to perform an orientation survey at the planned sampling

site prior to an actual collection campaign for reference materials. An orientation survey also

helps in the selection of the right sampling material in the planned area. The reference

material should be chosen so that it can be easily and rapidly sampled, because the time used

for sampling increases the cost of prepared RMs. This also complicates the production of RMs.

An orientation survey to find extremely high concentrations would be preferred such that Au

and its pathfinder elements are well above the LDLs.

Even though running the subsamples with several analytical methods increases the costs of an

off-the-self SRM, the number of pre-analysed subsamples still has to be significant enough

(recommend minimum 7) in order to produce reliable statistics to be delivered with the SRMs.

The number of subsamples has to be considered in the planning stage for off-the-self SRMs

such that the amount of remaining material is considerable enough for long-term use.

In the current investigation, the laboratory results run on the same material were treated

independently, because each laboratory conducted slightly different procedures, which

affects the concentration levels. In future work, a statistical procedure following the ISO

Guide 35:2017 with the non-paired Student’s t-test and Tukey’s statistical analyses could be

used to assess inter-method variability for each element to test the null hypothesis that the

elemental contents are drawn from different populations. Alternatively, Ellison (2015)

recommends improvements to the homogeneity criteria for reference materials.


26

5.2 Recommendations for producing soil reference materials

The selected sample material should contain suitable concentrations of the elements of

interest. Therefore, an orientation survey at the planned sampling site is advisable.

If the Ah horizon is to be collected for reference material, ensure that the horizon is thick

enough for sampling in the selected area.

Store the collected material in a large plastic bag.

Sample preparation times were recorded during the development of the SRM protocol in the

UpDeep project. It is most cost-efficient to prepare a large bulk quantity of RM at once such

that the analysis of subsamples results in a large number of prepared SRMs.

A large subsample set increases the homogeneity of SRMs.

A relatively small amount of reference material can be homogenized in the field, but larger

amounts may be easier to homogenize in a laboratory.

Drying, selection of the sieve size and sieving of the reference material depends on the

selected analytical methods.

Store the subsamples in plastic zip-lock bags.

Storage of soil SRMs is most cost-efficient at room temperature in a dry place. If unprocessed

RMs with natural moisture levels are required, e.g. for ionic leaching, then storage in a freezer

or a fridge is required.

When producing new reference sample materials, the most commonly used analytical

methods (sieving to a commonly used particle size, extraction techniques) should primarily be

performed. Additional analytical methods for subsamples can be performed later if required.

5.3 Recommendations for producing plant reference materials

Only species that are abundant at a sampling site should be selected for SRM production,

because the sampling time is a major cost in plant SRM production.

A large amount of plant material is required to construct a large SRM bank that would last a

number of years for commercial purposes. Harvesting entire mature trees could considerably

reduce the sampling time. Then, samples could be collected at one location from the height of

the entire tree. Doing this, however, would compromise the homogeneity of the sample

material, since concentrations vary according to the position of the branches or bark along

the trunk (Dunn, 2007). Depending on the conditions set by the landowner, sampling of one

individual tree might be the most feasible option.

Bark samples should be collected into large paper bags, because fine bark powder, once dry,

seeps out of porous cotton bags.

Similarly, foliage samples should be collected into cotton bags or rice sacks, because the

drying of samples makes the branches and leaves brittle and needles tend to break off the


27

stems. The firewood sacks we tested in the UpDeep project for foliage samples are not good

for storing and transporting conifer foliage samples.

Similar sampling instructions apply to bank sampling as to routine sampling: Avoid touching

the samples without gloves, cut with clippers and scrapers having heavy-metal-free blades,

and keep samples clean and dry during collection and transportation.

A large industrial oven is required for drying of the sampled material.

Separation of the needles/leaves from twigs is a major expense in the construction of an SRM

bank. Mechanical procedures for this task should be developed in future projects to make it

faster. In addition, drying at a higher temperature of 80 oC may dramatically reduce the

separation time (pers. comm. Colin Dunn, 1 November 2019).

The bottom sieve of the Retsch cutting mill, especially the one with a screen size of 0.5 mm, is

rapidly clogged by resin and wax from needles. Therefore, cleaning of the bottom sieve as

well as the cutting blades takes a considerable amount of time during the grinding of needles.

A vacuum/cyclone creating a vacuum (low pressure) in the milling chamber would improve

the milling efficiency by helping the light material to be sucked through the screen.

A finer milling grain size than 0.5 mm may make dry-milled biogeochemical SRMs more

homogeneous. Future work is required to test this.

6 LITERATURE REFERENCES

Agnico Eagle, 2015. Annual Report. http://s1.q4cdn.com/150142668/files/doc_financials/ 2015/2015-Annual-Report.pdf.

Dubé, B., Gosselin, P., Mercier-Langevin, P., Hannington, M., Galley, A., 2007. Gold-rich volcanogenic massive sulphide deposits. Geological Association of Canada, Mineral Deposits Division, Special Publication. 5. 75–94.

Bloom, L., 2002. Analytical Services and QA/QC. https://www.explorationgeochem.com/images/files-NOT-CRM/ASL_QA_QC.pdf.

Ellison, S.L.R., 2015. Homogeneity studies and ISO Guide 35:2006. https://link.springer.com/content/pdf/10.1007%2Fs00769-015-1162-z.pdf.

Emsbo, P., Groves, D.I., Hofstra, A.H., Bierlein, F.P., 2006. The giant Carlin gold province: a protracted interplay of orogenic, basinal, and hydrothermal processes above a lithospheric boundary. Mineralium Deposita 41, 517–525.

https://www.explorationgeochem.com/images/files-NOT-CRM/ASL_QA_QC.pdf

https://www.explorationgeochem.com/images/files-NOT-CRM/ASL_QA_QC.pdf


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Geboy, N.J., Eagle, M.A., 2011. Quality assurance and quality control of geochemical data: a primer for the research scientists. U.S. Geological Survey, Open-File report 20111187, 22 p., 2 app.

Geological Survey of Finland, 2020. Kuotko. Mineral Deposit Report, 19 s. Electronic resource available at: http://tupa.gtk.fi/karttasovellus/mdae/raportti/387_Kuotko.pdf

Goldfarb, R.J., Groves, D.I., 2015. Orogenic gold: Common or evolving fluid and metal sources through time. Lithos 233 (15), 2–26.

Gopalakrishnan, R., 2005. Preparation and certification of international rock standards. Journal of Geological Society of India, Vol 65, 658–662.

Härkönen, I., Pankka, H., Rossi, S., 2000. Summary report: The Iso-Kuotko gold prospects, northern Finland. Geological Survey of Finland (GTK), Report No. C/M06/2744/00/1/10.

ISO Guide 17034. General requirements for the competence of reference material producers. International Organisation for Standardisation (ISO), Geneva, 2016, pp. 24.

ISO Guide 30, Reference materials - Selected terms and definitions, International Organisation for Standardisation (ISO), Geneva, 2015, pp. 8

ISO Guide 31, Reference materials — Contents of certificates, labels and accompanying documentation, International Organisation for Standardisation (ISO), Geneva, 2015, pp. 10.

ISO Guide 35. Reference materials— Guidance for characterization and assessment of homogeneity and stability. International Organization for Standardization, Geneva, Fourth edition 2017-08, 105 p.

Dunn, C.E., 2007, Biogeochemistry in Mineral Exploration, (Handbook of Exploration and Environmental Geochemistry 9, Series editor, M. Hale), Elsevier, Amsterdam (462 pp.)

Kalra, Y.P., 1998. Handbook of Reference Methods for Plant Analysis. Soil and Plant Analysis Council, Inc., CRC Press, 287.

Mackey, E.A., Christopher, S.J., Lindstrom, R.M., Long, S.E., Marlow, A.F., Murphy, K.E., Paul, R.L., Popelka-Filcoff, R.S., Rabb, S.A., Sieber, J.R., Spatz, R.O., Tomlin, B.E., Wood, L.J., Yu, L.L., Zeisler, R., 2010. Certification of three NIST renewal soil standard reference materials for element content: SRM

http://tupa.gtk.fi/karttasovellus/mdae/raportti/387_Kuotko.pdf


29

2709a San Joaquin Soil, SRM 2710a Montana Soil I, and SRM 2711a Montana Soil II. National Institute of Standards and Technology Special Publication 260-172, 39 p.

Molnár, F., Middleton, A., Stein, H., O`Brien, H., Lahaye, Y., Huhma, H., Pakkanen, L., Johanson, B., 2018. Repeated syn- and post-orogenic gold mineralization events between 1.92 and 1.76 Ga along the Kiistala Shear Zone in the Central Lapland Greenstone Belt, northern Finland. Ore Geology Reviews 101, 936–959.

Okai, T., 2016. Development and utilization of geochemical reference materials – Reliability improvement in the analysis of geological materials. Synthesiology 9:2, 60–72.

Patten, C.G.C., Pitcairn, I.K., Teagle, D.A.H., Harris, M., 2016. Mobility of Au and related elements during the hydrothermal alteration of the oceanic crust: implications for the sources of metals in VMS deposits. Mineralium Deposita 51:2, 179–200.

Pearson, R.G., 1963. Hard and soft acids and bases. Journal of the American Chemical Society, 85, 3533–9.

Rawlins, B.G., McGrath, S P, Scheib, A J, Breward, N, Cave, M, Lister, T R, Ingham, M, Gowing, C and Carter, S., 2012. The advanced soil geochemical atlas of England and Wales. British Geological Survey, Keyworth. Available at: nora.nerc.ac.uk/id/eprint/18016/1/Advanced_Soil_Geochemical_Atlas_of_England_and_Wales.pdf

Reimann, C., Filzmoser, P., Garrett, R., Dutter, R. 2008. Statistical data analysis explained: applied environmental statistics with R. John Wiley & Sons Ltd, England. 343 p.

Robb, L., 2005. Introduction to Ore-Forming Processes. Blackwell, Oxford. 373 p.

Sarapää, O., Sarala, P., 2013. Rare earth element and gold exploration in glaciated terrain: example from the Mäkärä area, northern Finland. Geochem. Explor. Environ. Anal. 13,

131–143.

Sillitoe, R.S., Hedenquist, J.W. 2003. Linkages between volcanotectonic setting, ore-fluid compositions, and epithermal precious metal deposits. Soc. Econ. Geol. Spec. Publ. 10, 315–343.

Tooth, B., Brugger, J., Ciobanu, C., Liu, W. 2008. Modelling of gold scavenging by bismuth melts coexisting with hydrothermal fluids. Geology 36, 815–818.


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Zhu, Y., An, F., Tan, J., 2011. Geochemistry of hydrothermal gold deposits: A review. Geoscience Frontiers 2:3, 367–374.

7 ACKNOWLEDGEMENTS

Jukka Välimaa (Agnico-Eagle Finland Ltd) allowed sampling for the UpDeep SRM bank at the Tiira Au prospect. Heidi Kalliosalo (Lapland University of Applied Sciences) and Hanna Koskinen (University of Oulu) helped with sampling. Päivi Heikkilä, Viena Arvola and Jenni Siivola (GTK) conducted the separation of the foliage samples. Mari Pölönen and Hannu Karhu conducted the sample preparation at GTK Mintec. Pasi Eilu and Juhani Ojala (GTK) provided expertise on Au deposits and their pathfinders. Colin Dunn (Colin Dunn Consulting) provided valuable advice throughout the work. Timo Tarvainen (GTK) carried out an external review of this report and Roy Siddal revised the language. Thank you for your contribution!

The UpDeep project (Upscaling deep buried geochemical exploration techniques into European business, 2017-2020, htts://projects.gtk.fi/updeep) was an EIT Raw Materials-funded project focusing on the development of a geochemical exploration service having a low environmental impact that specializes in surface geochemical techniques. The UpDeep surface geochemical concept can aid the exploration industry in identifying and prioritizing potential exploration targets by reducing the time and cost while improving reliability in target detection. Surface geochemical exploration is based on analysing trace amounts of metals or other elements and soil hydrocarbons in plants and soil horizons to discover deeply buried mineralisation. This activity received funding from the European Institute of Innovation and Technology (EIT), a body of the European Union, under Horizon 2020, the EU Framework Programme for Research and Innovation.

8 APPENDICES

Appendix 1. Laboratory input data files for the UpDeep SRM bank. UpDeep_SRM_bank_input_files.

Appendix 2. Output data files of the UpDeep SRM bank. UpDeep_SRM_bank_output_files.

qc_ SRMname.csv, LDL=lower detection limit, n_LDL = number of samples under the LDL,

pct_LDL = percentage of samples under the LDL, UDL = upper detection limit,

n_UDL = number of samples over the UDL, pct_UDL = percentage of samples over the UDL,

pct_LD = percentage of samples <LDL or >UDL, pct_discr = percentage of samples that are

rounded/discretized by the laboratory (calculated for all 10 samples), sd, mean and median of

the analysed UpDeep SRMs, SD_externalSRMname_C = standard deviation of preanalysed

concentrations, RSD_ externalSRMname_C = relative standard deviation of preanalysed

concentrations, SD_ externalSRMname = standard deviation of the external SRMs analysed


31

with UpDeep SRMs, RSD_ externalSRMname = relative standard deviation of the external

SRMs analysed with UpDeep SRMs.

descript_SRMname.csv, descriptive statistics of the homogenized SRM aliquots (n = 10),

MIN = minimum concentration, Q_0.05 = 5th percentile, Q1 = 25th percentile, MEAN-log,

logged mean, MAX = maximum value, SD = standard deviation, MAD = median absolute

deviation, IQR = interquartile range, CV% = RSD% = coefficient of variation, CVR% = the robust

coefficient of variation (see Reimann et al. 2008)

QC_ SRMname.pdf, Distribution plots of the analysis results for routine samples. Histogram,

Tukey boxplot, ECDF and CP plots on an absolute concentration scale and on a log scale. Plot

QAQC1 depicts the concentrations of single elements in the sequence of analysis, and QAQC2

the concentration of external SRMs in the order of analysis compared to the mean and

standard deviation of pre-analysed concentrations.

SRMname_realunits.csv. File of the UpDeep SRM aliquot (n = 10) concentrations in the

original units. Can be used by the clients of UpDeep SRMs as pre-analysed values. These files

are laboratory specific.

SRMname_ppm.csv. File of the UpDeep SRM aliquot (n = 10) concentrations in ppm. Can be

used by the clients of UpDeep SRMs as pre-analysed values. These files are laboratory specific.

ggplots_SMRname_realunits.pdf and ggplots_SMRname_ppm.pdf. UpDeep SRM plots

including all analysed elements and their a) concentration boxplots, b) RSD% and median

normalized concentration boxplots; a) can be used to quickly view the concentration ranges of

each element, and b) and c) to evaluate the homogeneity of the elemental analyses.

Appendix 3. Reports of the ready SRMs in the UpDeep biogeochemical SRM bank:

UpDeep_ORG_Ah1

UpDeep_MIN_B1

UpDeep_MIN_B3

UPDEEP_JUN_NEED_ASH

UPDEEP_JUN_TWIG_ASH

UPDEEP_SPRU_BARK_DRY



Appendix 4. Summary of the UpDeep soil reference material samples, available elements and their homogeneity expressed as the relative standard deviation (RSD%). Elements with RSD% < 5 are in green, RSD% = 5–15 in orange and RSD% > 15 in red; NA = three or less samples between the lower and upper detection limits and ‘-‘ = element not analysed. ME-MS07 is sodium pyrophosphate leach, ME-MS23 is Ionic leachTM, AQ250 is modified aqua regia digestion, LH103 is partial leach with 0.1 M sodium pyrophosphate and ME-MS41W-REE is weak acid leach.


32

Element Unit CV % Unit CV % Unit CV % Unit CV % Unit CV % Unit CV % Unit CV % Unit CV %

Ag ppm 33 ppm 22 ppm 8 ppm 114 ppb 7 ppb 7 ppb 21 ppm 7

Al ppm 3 ppm 2 % 3 % 3 - % 3 ppm 5 % 6

As ppm 10 ppm 15 ppm 8 ppm 88 ppb 17 ppm 9 ppb 8 ppm 9

Au ppm NA ppm NA ppm 87 ppm 256 ppb 26 ppb NA ppb NA ppm 105

B ppm 27 ppm 31 ppm NA ppm NA - ppm NA - ppm NA

Ba ppm 3 ppm 2 ppm 3 ppm 3 ppb 11 ppm 4 ppb 5 ppm 4

Be ppm 7 ppm 13 ppm 3 ppm 8 ppb 7 ppm 43 ppb 11 ppm 10

Bi ppm 13 ppm 11 ppm 4 ppm 12 ppb 11 ppm 13 ppb 8 ppm 5

Br ppm 14 ppm 13 - - ppm 7 - - -

Ca ppm 15 ppm 20 % NA % NA ppm 9 % 6 ppm 8 % 0

Cd ppm 30 ppm 47 ppm 7 ppm 16 ppb 5 ppm 4 ppb 8 ppm 6

Ce ppm 4 ppm 2 ppm 6 ppm 7 ppb 5 ppm 6 ppb 5 ppm 8

Co ppm 7 ppm 3 ppm 5 ppm 6 ppb 3 ppm 5 ppb 4 ppm 14

Cr ppm 3 ppm 1 ppm 2 ppm 4 ppb 4 ppm 6 - ppm 10

Cs ppm 11 ppm 11 ppm 5 ppm 5 ppb 5 ppm 6 ppb NA ppm 9

Cu ppm 4 ppm 2 ppm 3 ppm 11 ppb 4 ppm 8 ppb 12 ppm 10

Dy ppm 5 ppm 5 ppm 5 ppm 7 ppb 4 ppm 5 ppb 10 ppm 11

Er ppm 8 ppm 6 ppm 5 ppm 7 ppb 3 ppm 10 ppb 7 ppm 8

Eu ppm 7 ppm 7 ppm 4 ppm 8 ppb 5 ppm 5 ppb 7 ppm 7

Fe ppm 4 ppm 1 % 3 % 2 ppm 4 % 2 ppm 3 % 8

Ga ppm 5 ppm 2 ppm 3 ppm 5 ppb 8 ppm 6 ppb 8 ppm 9

Gd ppm 7 ppm 5 ppm 5 ppm 7 ppb 4 ppm 10 ppb 6 ppm 9

Ge ppm 6 ppm 8 ppm 7 ppm 9 ppb 7 ppm NA ppb NA ppm 49

Hf ppm 10 ppm 9 ppm 5 ppm 3 ppb 5 ppm NA ppb 8 ppm 57

Hg ppm 29 ppm NA ppm 9 ppm 10 ppb 5 ppb 7 ppb NA ppm 7

Ho ppm 5 ppm 5 ppm 5 ppm 8 ppb 3 ppm 9 ppb 9 ppm 12

I ppm 6 ppm 4 - - ppm 4 - - -

In ppm 26 ppm 30 ppm 10 ppm 13 ppb 9 ppm 34 ppb 21 ppm 6

K ppm 5 ppm 2 % NA % NA - % NA ppm 2 % 0

La ppm 4 ppm 3 ppm 7 ppm 6 ppb 5 ppm 6 ppb 6 ppm 7

Li ppm 7 ppm 5 ppm 5 ppm 7 ppb 15 ppm 18 ppb NA ppm 36

Lu ppm 13 ppm 12 ppm 5 ppm 7 ppb 3 ppm 15 ppb 10 ppm 10

Mg ppm 5 ppm 2 % 6 % 3 ppm 9 % 12 ppm 4 % 36

Mn ppm 20 ppm 2 ppm 9 ppm 3 ppm 13 ppm 8 ppb 8 ppm 23

Mo ppm 12 ppm 8 ppm 5 ppm 5 ppb 11 ppm 11 ppb 17 ppm 12

Na - - % 15 % NA - % 11 - % 26

Nb ppm 4 ppm 2 ppm 5 ppm 5 ppb 7 ppm 7 ppb 11 ppm 79

Nd ppm 6 ppm 3 ppm 5 ppm 7 ppb 5 ppm 7 ppb 7 ppm 7

B-horizon samples Ah-horizon samples

Up

De

ep

_MIN

_B1

_ALS

ME-

MS0

7

Up

De

ep

_MIN

_B3

_ALS

ME-

MS0

7

Up

De

ep

_MIN

_B1

_ALS

ME-

MS4

1W

-REE

Up

De

ep

_MIN

_B3

_ALS

ME-

MS4

1W

-REE

Up

De

ep

_MIN

_B2

_ALS

ME-

MS2

3

Up

De

ep

_OR

G_A

h1

_BV

AQ

25

0

Up

De

ep

_OR

G_A

h1

_BV

LH1

03

Up

De

ep

_OR

G_A

h1

_ALS

ME-

MS4

1W

-REE


33

Element Unit CV % Unit CV % Unit CV % Unit CV % Unit CV % Unit CV % Unit CV % Unit CV %

Ni ppm 5 ppm 4 ppm 3 ppm 12 ppb 5 ppm 3 ppb 7 ppm 9

P - - % 3 % 4 - % 9 - % 7

Pb ppm 5 ppm 8 ppm 4 ppm 18 ppb 4 ppm 4 ppb 3 ppm 4

Pd - - ppm NA ppm 199 ppb 24 ppb NA - ppm NA

Pr ppm 5 ppm 4 ppm 5 ppm 7 ppb 6 ppm 7 ppb 5 ppm 7

Pt - - ppm NA ppm NA ppb NA ppb NA - ppm NA

Rb ppm 4 ppm 6 ppm 3 ppm 4 ppb 4 ppm 4 ppb 6 ppm 10

Re ppm NA ppm NA ppm NA ppm NA ppb 11 ppb NA ppb NA ppm NA

S - - % NA % NA - % 8 - % 12

Sb ppm 12 ppm 10 ppm 16 ppm 97 ppb 26 ppm 9 ppb 40 ppm 8

Sc - - ppm 5 ppm 5 ppb 5 ppm 11 ppb 6 ppm 43

Se ppm 28 ppm 40 ppm 11 ppm 13 ppb 8 ppm 17 ppb NA ppm 9

Sm ppm 5 ppm 8 ppm 5 ppm 7 ppb 6 ppm 4 ppb 5 ppm 9

Sn ppm 9 ppm 4 ppm 14 ppm 11 ppb 9 ppm 7 ppb 9 ppm 9

Sr ppm 10 ppm 8 ppm 5 ppm 5 ppb 45 ppm 5 ppb 5 ppm 4

Ta ppm 6 ppm 6 ppm 18 ppm NA ppb 5 ppm NA ppb NA ppm 61

Tb ppm 9 ppm 12 ppm 4 ppm 7 ppb 3 ppm 8 ppb 8 ppm 8

Te ppm 55 ppm NA ppm 27 ppm 27 ppb 9 ppm NA ppb NA ppm 40

Th ppm 3 ppm 3 ppm 4 ppm 11 ppb 4 ppm NA ppb 9 ppm 51

Ti ppm 5 ppm 2 % 3 % 3 ppb 6 % 17 ppm NA % 11

Tl ppm 20 ppm 26 ppm 5 ppm 6 ppb 8 ppm 23 ppb NA ppm 10

Tm ppm 11 ppm 9 ppm 5 ppm 6 ppb 4 ppm 13 ppb 8 ppm 8

U ppm 4 ppm 3 ppm 2 ppm 4 ppb 3 ppm 15 ppb 6 ppm 7

V ppm 6 ppm 2 ppm 5 ppm 5 - ppm 5 ppb 10 ppm 11

W ppm 9 ppm 10 ppm 5 ppm 8 ppb 5 ppm NA ppb 11 ppm 26

Y ppm 4 ppm 4 ppm 4 ppm 7 ppb 5 ppm 6 ppb 6 ppm 8

Yb ppm 5 ppm 4 ppm 5 ppm 8 ppb 3 ppm 8 ppb 11 ppm 10

Zn ppm 6 ppm 2 ppm 3 ppm 5 ppb 3 ppm 5 ppb 4 ppm 5

Zr ppm 3 ppm 2 ppm 6 ppm 5 ppb 4 ppm NA ppb 7 ppm 97

B-horizon samples Ah-horizon samples

Up

Dee

p_M

IN_B

1_A

LS

ME-

MS0

7

Up

Dee

p_M

IN_B

3_A

LS

ME-

MS0

7

Up

Dee

p_M

IN_B

1_A

LS

ME-

MS4

1W-R

EE

Up

Dee

p_M

IN_B

3_A

LS

ME-

MS4

1W-R

EE

Up

Dee

p_M

IN_B

2_A

LS

ME-

MS2

3

Up

Dee

p_O

RG

_Ah

1_B

V

AQ

250

Up

Dee

p_O

RG

_Ah

1_B

V

LH10

3

Up

Dee

p_O

RG

_Ah

1_A

LS

ME-

MS4

1W-R

EE


34

Appendix 5. Summary of the UpDeep biogeochemical reference materials, available elements and their homogeneity expressed as the relative standard deviation (RSD%). Elements with RSD% < 5 are in green, RSD% = 5–15 in orange and RSD% > 15 in red; NA = three or less samples between the lower and upper detection limits and ‘-‘ = element not analysed. If RSD = 0, the values are heavily discretised, i.e. rounded, by the laboratory. Light rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd) are bolded in black and heavy rare earth (Y, Tb, Dy, Ho, Er, Tm, Yb, Lu) elements are bolded in grey. Explanations for the analytical techniques used in the laboratories can be found in Table 2.

ASHED SRMs DRY WEIGHT SRMs

JUN_TWIG_ASH JUN_NEED_ASH SPRU_BARK_DRY SPRU_TWIG_DRY SPRU_NEED_DRY

ele

me

nt

UP

DE

EP

_P

INE

_B

AR

K_A

SH

_A

LS

UP

DE

EP

_JU

N_T

WIG

_A

SH

_A

LS

UP

DE

EP

_JU

N_T

WIG

_A

SH

_B

VA

cm

e

UP

DE

EP

_JU

N_T

WIG

_A

SH

_A

ctlabs

UP

DE

EP

_JU

N_N

EE

D_A

SH

_A

LS

UP

DE

EP

_JU

N_N

EE

D_A

SH

_B

VA

cm

e

UP

DE

EP

_JU

N_N

EE

D_A

SH

_A

ctlabs

UP

DE

EP

_S

PR

U_B

AR

K_D

RY

_A

LS

UP

DE

EP

_S

PR

U_B

AR

K_D

RY

_B

VA

cm

e

UP

DE

EP

_S

PR

U_B

AR

K_D

RY

_A

ctla

bs

UP

DE

EP

_S

PR

U_T

WIG

_D

RY

_A

LS

UP

DE

EP

_S

PR

U_T

WIG

_D

RY

_B

VA

cm

e

UP

DE

EP

_S

PR

U_T

WIG

_D

RY

_A

ctla

bs

UP

DE

EP

_S

PR

U_N

EE

D_D

RY

_A

LS

UP

DE

EP

_S

PR

U_N

EE

D_D

RY

_B

VA

cm

e

UP

DE

EP

_S

PR

U_N

EE

D_D

RY

_A

ctla

bs

Ag 7.6 10.6 9 NA 6.5 9.8 NA 10.4 7.7 NA 5.2 12.4 NA 17.9 14.4 NA

Al 1.6 0 6.2 3.8 0 0 9 0 NA - 0 NA - 0 NA -

As 9.7 31 40.5 NA 14.5 34 NA 5.6 24.7 7.7 7.2 11.1 5.2 18.5 NA 12.5

Au 185.4 25.4 20.2 NA 113.9 116.9 NA 26.7 49 - 21 77.3 - NA 40.3 -

B 1.7 1.7 6 9.3 1.3 4.6 2.9 0 11.6 3.2 5.9 10.9 2.4 4.6 8.6 2.6

Ba 1.7 1.4 2.2 2 0.8 1.5 2 1.1 4.7 1.3 1.7 5 5.5 1.6 4 2.8

Be 8.7 12.1 NA NA 6.8 NA 11.3 0 NA NA NA NA NA 8.1 NA NA

Bi 29.7 6.5 NA NA 4.2 NA NA 4 NA 6.8 32.5 NA NA NA NA NA

Br - 6.4 - - - - - - - - - - - - -

Ca 1.6 1.4 2.4 2 0.7 1.9 1.8 1.5 3.8 1.7 1.7 4.6 1.5 1.8 5 2.1

Cd 1.8 1.8 4.6 4.4 1.8 5.5 2.5 4.8 8 2.8 3.2 11.7 5.6 5.8 16.6 8.3

Ce 3.4 1.5 3.6 1.7 1.8 3.7 1.7 9.9 NA 12.8 3.2 NA 24.7 6 NA 28.7

Cl - 8.3 - - - - - - - - - - - - -

Co 6.2 4.4 4.4 2.2 1.6 5.5 1.8 5 7.8 1.8 3.1 10 1.7 3.6 11.7 5.6

Cr 7.7 9.6 5.5 NA 3.9 7.9 NA 19.4 11 6.4 29.8 7 8.6 47.5 3.9 4.7

Cs 3 7.8 5.2 5.7 5.7 3.9 5 4.6 0 3.7 3.4 4.6 2.6 7.3 0 2.9

Cu 1.5 2.2 2.2 2 1.2 4.1 1.1 3.1 3.6 1.2 2.4 2.3 7.5 3.7 31.6 4

Dy 3.9 7.5 10 3.9 3.5 13.9 2.9 NA 5.8 11.7 NA 5.3 13.2 NA 8

Er 4.5 9.3 11.3 5.6 7.5 11.2 5.2 NA 7.4 18 NA 6.4 NA NA 6.4

Eu 4 13.2 15.7 3.5 8.6 15.3 1.9 NA 6.8 NA NA 8.3 NA NA 15.1

F - NA - - - - - - - - - - - - -

Fe 9.4 2.9 0 3.1 4.6 3.9 5.2 8 8.6 3.6 4.8 8 5.7 4 10.9 2.7

Ga 5.6 3.4 19.2 19.2 3.6 10.2 NA 6.8 NA 10.1 4.8 NA 12.5 9.6 NA 19.4

Gd 3.5 4.2 14.1 1.6 5.3 13.6 3.9 NA 6.1 10.6 NA 5.2 25.5 NA 12.8

Ge 14.1 18.6 NA NA NA NA NA 18.3 NA 25.1 NA NA 30.7 NA NA NA

Hf 14.7 14.3 NA NA 23.9 NA NA 10.2 58.8 17.5 NA NA NA NA NA NA

Hg 50.9 NA - - NA - - 7.8 3.4 7.5 8 14 NA 6.7 8.5 NA

Ho 3.8 7.3 13.1 5.1 5 21.1 4.1 NA 4.6 0 NA 8.9 11.1 NA 6.1

I - 9.6 - - - - - - - - - - - - -

In 23 NA NA 25.9 NA NA 48.2 0 NA NA NA NA NA NA NA NA

K 1.8 1.5 1.8 2.8 0.9 1.2 1.5 0 4.6 2.2 2 4.4 2 1.9 7 3

La 3.3 1.3 3.7 1.5 1.8 4.6 1.7 8.7 9.6 13.8 3.6 16.6 20.4 6.9 35.1 16.3

Li 5.3 5.4 6.8 3.1 2.2 3.6 1.5 0 42.6 NA 0 27.9 NA NA 24.7 NA

Lu 3.4 8.8 NA 10.8 10.9 NA 9.5 NA NA NA NA NA NA NA NA

Mg 1.8 1.5 2.6 2.2 0.9 1.5 1.1 0 5.2 1.6 1.8 4.4 1.6 1.7 4.4 1.5

Mn 1.4 1.5 2.3 1.7 0.6 NA 0.8 1.3 3.9 2 1.7 4.6 2.4 2 3.2 2.5

Mo 3.4 4.8 4.8 15.1 4.4 4.9 15.2 36.9 15.1 17.3 13.2 14.3 6 14.6 15.7 4.7


35

Na 1.3 2.8 2.6 7.7 1.1 2 5.4 15.4 9.1 5.7 3.4 11.2 2.4 6.2 13.2 9.7

Nb 2.8 6 4.1 6 10.3 7.3 6.4 8.1 NA 11.6 7.2 NA 8.7 22.1 NA 10.2

Nd 4 2.9 6.9 2.4 2.8 4.7 3.3 36.6 10.4 4.9 22.5 12.6 18.3 NA 18.2

Ni 3.1 3.7 4.4 1.7 1.2 1 1.1 8.9 9.4 15.3 4 10.9 4.8 5.4 0 9.1

P 1.6 1.4 3.6 - 0.9 5 - 4.7 7.7 - 1.8 4.7 - 1.8 5 -

Pb 38.6 2.3 3.5 2.5 1.9 4.3 2.7 3.9 5 6.8 4 13.4 18 20.2 13.9 123.4

Pd 49 NA NA 1.9 NA NA 1.7 10.2 NA NA NA NA NA NA NA NA

Pr 3.4 2.7 4.6 2.5 4.2 5.9 2.7 NA 9.9 4.7 NA 16.5 15.7 NA 20

Pt 13.7 26.9 31.5 30.2 NA 44.5 NA 103.1 NA NA NA NA NA 33.3 NA NA

Rb 3.2 3.3 3.7 2.2 1.2 3.1 2 4.5 3.8 1.8 2.3 3.5 1.5 1.6 4 1.1

Re 36.9 NA NA 38.2 NA NA 14.6 0 NA NA NA NA NA NA NA NA

Ru - - - NA - - NA - - - - - - - -

S 1.6 3.5 3.7 - 1.4 2 6 7.8 19.2 - 0 NA - 4 34.3 -

Sb 11.8 6.3 3 4.8 10.9 6.8 - 11.8 10 44.1 14.3 11.1 12.6 15.1 NA NA

Sc 6 3.1 21.1 13.6 2.5 6.2 NA 14 52.7 NA 8 43.8 NA 4.4 28.7 NA

Se 6 6.2 NA NA 6.5 NA NA 7.2 21 49.4 11.5 23.6 50.9 44.1 31.6 NA

Si - - - NA - - NA - - - - - - - -

Sm 5.1 8.2 13.5 3.8 7.3 9.9 7.3 NA 9.1 15.4 NA 10.8 28.7 NA 21.3

Sn 3.6 10.9 0 NA 6.9 19.2 NA 20.6 NA NA 13.2 NA NA 28.7 NA NA

Sr 1.7 1.5 3.9 2 1 4 0.8 3.9 3.7 1.4 1.5 5.4 1.1 1.4 4.5 0.9

Ta 8.3 NA NA NA NA NA 17.9 8.1 NA 25.1 NA NA 13.2 NA NA 15.9

Tb 4 6.8 14.3 2.7 5 15.2 4.2 NA 10.9 0 NA 6.6 13.1 NA NA

Te 76 NA 25.4 122.8 NA 22.1 113.4 0 NA NA NA NA NA NA NA NA

Th 5 5.8 NA 19.6 6.7 NA 6.5 14.8 NA 40.3 14.8 NA 44.2 NA NA 66.5

Ti 3.8 0 4.3 3.2 0 3.6 10.4 0 0 10.5 NA 14.3 6.8 NA 35.1 16.4

Tl 11.2 4.8 0 8.5 17.9 NA NA 3.7 21 3.1 2.2 11.2 2 2.9 7.7 2.1

Tm 4.8 5 NA 5.6 10 NA 6.7 NA NA NA NA NA NA NA NA

U 2.5 6.2 NA 9.3 5.5 NA 8 0 NA 116.1 NA NA 37.2 NA 204.4 131.5

V 5.6 4.5 0 NA 2 0 NA 3.2 NA 2.7 3.6 NA 4.1 13.8 NA 5.9

W 5.4 4.4 10.1 13 3.7 7.4 4.7 0 NA NA 0 NA NA NA NA NA

Y 3.9 3.7 4.6 2.5 2.4 3.5 2.5 5.6 8.7 4.2 5.3 10.3 7.6 7.3 11.3 4

Yb 2.3 9.6 15.1 7.8 8.5 16.3 5.4 NA 11.7 NA NA 9.4 NA NA 10.1

Zn 1.7 1.5 3.7 2 0.8 4 1 1.2 6.7 1.3 1.6 5.2 2 1.4 8.8 1.5

Zr 7.5 4.2 NA NA 4.3 NA NA 18.8 19.1 9.5 28.7 110.4 8 13.1 69 10.5

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