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PALEOMAGNETISM OF PROTEROZOIC NEWER DOLERITES DYKE SWARM IN THE SINGHBHUM CRATON, NE INDIA

By

KARASTIN KATUSIN

A THESIS PRESENTED TO THE GRADUATE SCHOOL

OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2017

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© 2017 Karastin Katusin

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To Daun, Jessica and Anthony Cespedes

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ACKNOWLEDGMENTS

This research was supported by the US National Science Foundation to J.G.

Meert (EAR13-47942 and EAR04-19101). I would like to thank my graduate advisor, Dr.

Joseph Meert for reminding me that hard work and perseverance are the keys to

success at any level and situation. I want to thank committee members, Dr. Ray Russo,

Dr. David Foster and Dr. George Kamenov for their support, helpful commentary and

guidance during my time with the Geological Sciences department. I would also like to

thank Dr. Manoj Pandit and Dr. Anup Sinha for the enjoyable companionship and in-the-

field guidance while in India. Thank you to the office staff, Pamela Haines and Carrie

Williams for answering all my questions and their unwavering support. I would like to

thank all of my lab mates, as well as fellow graduate students for their guidance,

support and friendship. Finally, I would like to thank my family for always believing in

me, never letting me doubt myself and reminding me that anything is possible if you

work hard enough.

.

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TABLE OF CONTENTS page

ACKNOWLEDGMENTS................................................................................................. 4

LIST OF FIGURES ........................................................................................................ 7

LIST OF ABBREVIATIONS ............................................................................................ 9

ABSTRACT.................................................................................................................. 10

CHAPTER

1 INTRODUCTION ................................................................................................... 12

Supercontinents .................................................................................................... 12

Regional Geology .................................................................................................. 16

2 METHODS ............................................................................................................ 29

Paleomagnetism .................................................................................................... 29

Rock Magnetic Studies .......................................................................................... 30

3 RESULTS .............................................................................................................. 31

Rock Magnetic Results .......................................................................................... 31

Northern (Jamshedpur) Sites .......................................................................... 31

Southern (Keonjhar) Sites ............................................................................... 32

Paleomagnetic Results .......................................................................................... 32

E-W Steeply Inclined Direction (Group 1) ........................................................ 32

NE-SW Shallowly Inclined Directions (Group 2) .............................................. 33

North Intermediate Inclination Direction (Group 3)........................................... 34

NW-SE Shallowly Inclined Direction (Group 4) ................................................ 35

E-W Intermediate Inclination Directions (Group 5 and 6) ................................. 35

4 DISCUSSION ........................................................................................................ 58

~1.77 Ga Dykes ..................................................................................................... 59

~2.2 Ga Dykes....................................................................................................... 61

North Group Direction ............................................................................................ 61

Global Reconstructions.......................................................................................... 62

5 CONCLUSIONS .................................................................................................... 73

LIST OF REFERENCES .............................................................................................. 75

BIOGRAPHICAL SKETCH ........................................................................................... 81

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LIST OF TABLES

Table page 3-1 All 2014 Paleomagnetic Results ........................................................................ 51

3-2 Paleomagnetic results from Group 1 ................................................................. 54

3-3 Paleomagnetic results from Group 2. ................................................................ 55

3-4 Paleomagnetic results from Group 3. ................................................................ 56

3-5 Paleomagnetic results from Group 4. ................................................................ 57

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LIST OF FIGURES

Figure page 1-1 Proterozoic supercontinent configuration of Columbia ....................................... 20

1-2 Configuration Laurentia’s Archean cratonic nuclei. ............................................ 21

1-3 Reconstruction of the supercontinent Rodina. ................................................... 22

1-4 Generalized geologic map of Peninsular India................................................... 23

1-5 Singhbhum Craton map .................................................................................... 24

1-6 Summary of the cratonic elements in the Singhbhum Craton. ........................... 25

1-7 Cross cutting trends of the Newer Dolerites dyke swarm, from our sampling locations. ........................................................................................................... 26

1-8 Cross cutting dyke relationships seen in the field. ............................................. 27

1-9 Map of our sampling site locations. ................................................................... 28

3-1 Map showing all sampling sites in the Singhbhum craton. ................................. 36

3-2 Geological map of the Singhbhum crustal provinces. ........................................ 37

3-3 Rose diagram depicting only dyke trends observed in the North study area. ..... 38

3-4 Orthogonal vector plots, equal area stereonets and thermal demagnetization behavior for the Jamshedpur low temperature/coercivity component dykes of the Singhbhum craton.. ..................................................................................... 39

3-5 Orthogonal vector plots, equal area stereonets and thermal demagnetization behavior for the Jamshedpur high temperature/coercivity component dykes of the Singhbhum craton.. ................................................................................. 41

3-6 Curie Temperature analysis of the Jamshedpur samples. Here both heating (Tch) and cooling (Tcc) curves are shown with the Curie temperature analyses. ........................................................................................................... 43

3-7 Rose diagram depicting only the dyke trends observed in the South study area. .................................................................................................................. 45

3-8 Orthogonal vector plots, equal area stereonets and thermal demagnetization behavior for the Keonjhar region of the Singhbhum craton ................................ 46

3-9 Curie Temperature analysis of the Keonjhar samples.. ..................................... 48

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3-10 Log bulk susceptibility versus distance plot of site i1427 contacts. .................... 49

3-11 Paleomagnetic results from 1637 dyke and country rock. .................................. 50

4-1 Shankar et al. (2014) 206Pb/207Pb ages from five baddeleyite fractions from the Newer Dolerite swarm. ................................................................................ 66

4-2 Sampling locations of 1636 (red star) and 1637 (yellow star), of the 1765 Ma WNW trending dyke. ......................................................................................... 67

4-3 Comparison of the Shankar et al. (2016) and this study pole position for the shallow NW-SE direction. .................................................................................. 68

4-4 Comparison of shallow NE-SE direction poles observed in the Singhbhum craton. Das et al. (1995; blue), Kumar and Bhalla (1984; yellow) and this study (pink) poles are shown which have age ranges from 2900-1765 Ma. ....... 69

4-5 Comparison of the Belica et al. (2014) and this study’s pole position for the ~2.2 Ga direction. .............................................................................................. 70

4-6 ~1.77 Ga paleogeographic reconstruction. Outlines are the Amazonia, North China, India, Baltica, Laurentia and Rio de la Playa cratons in a possible configuration during the supercontinent Columbia. ............................................ 71

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LIST OF ABBREVIATIONS

AF Alternating Field

CITZ Central Indian Tectonic Zone

D Declination

EB Eastern Block

Ga Billion Years

I Inclination

Ma Million Years

NE-SW Northeast-Southwest

NIB North Indian Block

NRM Natural Magnetic Remanence

NW-SE Northwest-Southeast

SIB South Indian Block

Tcc Cooling Curie Temperature

Tch Heating Curie Temperature

TUB Thermal Unblocking Temperature

VGP Virtual Geomagnetic Pole

α95 95 cone of confidence about the mean direction

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science

PALEOMAGNETISM OF PROTEROZOIC NEWER DOLERITES DYKE SWARM IN

THE SINGHBHUM CRATON, NE INDIA

By

Karastin Katusin

August 2017

Chair: Joseph Meert Major: Geology

We present new paleomagnetic results from the Singhbhum craton at 2.25 and

1.765 Ga. The Newer Dolerite dyke swarm varies in orientation, with the two major

trends being NW-SE and NE-SW. The NE-SW trending dykes are of 2.25 Ga

(Srivastava et al., 2016) and show a mean declination= 81°, inclination= 69° (α95=6°).

The paleomagnetic pole position for the Singhbhum craton at 2.25 Ga is 22°N, 126°E

(A95=9°). Our pole gives constraints on a unification age of the South Indian Block due

to the similar poles seen in the Singhbhum and Dharwar cratons.

The 1.76 Ga (Shankar et al., 2014) dykes primarily trend NW-SE, with a

declination= 43°, inclination= -3° (α95= 12°). The paleopole position for the 1.76 Ga age

is 45°N, 199°E (A95=10°). We also present a possible continental reconstruction for

~1.77 Ga, which shows some similarities with previously published models, but due to

the lack of poles at this age, we cannot adequately test a complete reconstruction.

We also note the presence of a low temperature component in both the

Jamshedpur and Keonjhar regions. This component has a Curie Temperature of 320°C,

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indicative of pyrrhotite. This pyrrhotite dominated remanence was primarily in seen the

northern Jamshedpur region.

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CHAPTER 1 INTRODUCTION

Supercontinents

Although the Archean and Proterozoic Eons encompass more than 75% of Earth

history, the onset of modern-style plate tectonics, the history of plate motion and the

evolving paleogeography of this vast interval of geologic time is still poorly defined (Li et

al., 2008; Meert and Santosh, 2017). In particular, several supercontinent (or

supercraton) configurations were proposed including, but not limited to, Columbia/Nuna

and Rodinia (Rogers and Santosh 2002; Meert, 2002; Zhao et al., 2004; Li et al., 2008;

Evans and Mitchell, 2011; Meert, 2012; Meert, 2014; Meert and Santosh, 2017; Figure

1-1). In contrast with the more recent supercontinent of Pangea, data are lacking that

provide tight control on the relationships between the various nuclei that comprise

Rodinia and Columbia. The limited information that does exist often leads to vastly

different models of supercontinent assembly and breakup (Rogers and Santosh 2002;

Zhao et al., 2004; Li et al., 2008; Evans and Mitchell, 2011; Meert, 2014; Meert and

Santosh, 2017). While the desire is to incorporate as many types of data as possible

into the tectonic models, only paleomagnetic studies coupled with geochronological

data provide quantitative tools for establishing the latitude and orientation information

required for a robust paleogeography.

Columbia/Nuna is thought to be the first large supercontinent. According to some

models, the formation of Columbia took place between 2.0-1.7 Ga through the

progressive accretion of cratonic fragments now marked by ancient orogenic belts

(Rogers and Santosh, 2002; Meert, 2002, 2014; Zhao et al., 2003, 2004; Roberts,

2013). Columbia is thought to remain a stable configuration from ~1.7 Ga to ~1.3 Ga

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(Roberts, 2013; Zhao et al.,2004). Rogers and Santosh (2002) argued for a Columbia

supercontinent based on three observations: (1) A lack of orogenic activity between 2.5

to 2.1 Ga; (2) widespread tectonism between ~2.1-1.8 Ga; (3) Mesoproterozoic rift

basins that are found in both India and Western North America. The name “Columbia”

comes from the similarities between the Mahanadi-Lambert and Godavari rifts of

India/East Antarctica and the Belt and Uinta rifts in the Columbia region of western

Laurentia around 1.5-1.6 Ga.

Zhao et al. (2002, 2003, 2004) provided a more detailed model that focused on

global collisional orogenic belts that developed between 2.1-1.8 Ga. The core of

Columbia “grew” from~1.8 to 1.3 Ga, via subduction-related accretion along the

continental margins of Laurentia, Baltica, Amazonia and North Australia (Zhao et al.,

2004). Fragmentation of Columbia began ~ 1.6 Ga, and is recorded by intra-continental

rift zones in Laurentia, Baltica, Siberia, North China and South Africa with final

dissolution of all cratons at ~1.2 Ga. The emplacement of ~1.35 to 1.27 Ga mafic dyke

swarms indicates the youngest ages in which cratons could have been linked in the

Columbia supercontinent (Zhao et al., 2002; 2004; 2011).

The configuration of Columbia included a core nucleus of Siberia, Laurentia and

Baltica, originally named “Nena” (Gower et al.,1990). Rogers (1996) modified the

“Nena” configuration to include “Artica” (Laurentia and Siberia), Baltica and East

Antarctica. Hoffman (1997) used Rogers (1996) definition of “Nena”, adding northern

and western Australia to create “Nuna”.

In addition to the issues related to the amalgamation and dispersal of Columbia;

the tectonic evolution of each crustal element within Columbia must be defined. As an

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example, “Laurentia” forms the core of both Columbia and Rodinia. Hoffman (1988)

outlined the progressive assembly of Laurentia and argued that Laurentia's growth

resulted from the closure of the intervening oceanic basins that originally separated the

Slave, Superior and Wyoming cratons (Figure 1-2). In the past 30 years, Hoffman’s

(1988) hypothesis found support from paleomagnetic studies (Kilian et al., 2016 and

sources within). In contrast, the history of Peninsular India assembly is poorly

constrained as is its location in Precambrian supercontinents.

In some Columbia reconstructions, India is positioned near Australia (Rogers and

Santosh, 2002) or East Antarctica and North China (Zhao et al., 2003; 2004). In the

Zhao et al (2003) model, the South India Block (SIB) is correlated to the Eastern Block

(EB) of the North China craton, linking Trans-North China Orogen (TNCO) as a

continuation of the Central Indian Tectonic Zone (CITZ). Zhao et al. (2003) based their

model on similarities between the sedimentary and magmatic records on both India and

North China during the 3.8 – 1.3 Ga interval. That original proposition no longer seems

tenable given age differences between the TNCO and the CITZ. Metamorphism and

deformation within the TNCO reaches a maxima around ~1.85 Ga (Zhao et al, 2002,

2003, 2004, 2011), but that age contrasts with most models for deformation/

metamorphism within the CITZ ages (2.5, 1.6, or 1.1-1.0 Ga; see below). In later models

(see Zhao et al.,2011), North China is simply placed alongside ‘another craton’ with no

mention of India.

Pisarevsky et al. (2013) used the Lakhna paleopole to compare India’s position

to Laurentia, Siberia and Baltica during the ~1.1 – 1.0 Ga interval. Their model

juxtaposes the Dharwar craton with Sarmatia. The western edge of Baltica is

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characterized as a prolonged accretionary margin as is the eastern margin of India.

Pisarevsky et al. (2013) implied that if this connection holds true, there could be a long

term (Paleo-MesoProterozoic), linear accretionary orogen spanning Baltica, India, and

Laurentia (connected to Baltica). In more recent models, Meert and Santosh (2017)

show that India can also be placed near Baltica or Amazonia ~1.45 Ga given the

liberties associated with paleomagnetic data.

Understanding the transition from Columbia to Rodinia is of critical importance,

(Rogers and Santosh, 2002; Meert, 2002; 2014; Zhao et al., 2002; Zhao et al., 2004,

Ernst et al., 2008; Meert and Santosh, 2017). The Rodinia and Columbia models; taken

at face value (i.e. Li et al., 2008; Zhao et al., 2003,2004), show only slight differences in

paleogeographic relationships (Meert, 2014). First, there is a group of “rigid core”

cratons (Laurentia, Baltica, Siberia), which have a consistent location and grouping

within both Columbia and Rodinia. Next, there are the India, Antarctica and Australia

cratons have a more malleable position within Rodinia. Lastly, the North China, South

China and Tarim cratons seem to wander in both super continental configurations.

Following the breakup of Columbia, some of the landmasses, most notably South

China, North China, Tarim and Kalahari, are thought to have drifted independently

before re-aggregating into the Rodina supercontinent (1.1-0.75 Ga; Torsvik et al., 1996;

Piper, 2000; Zhao, et al 2002; Zhao et al., 2003; Zhao et al., 2004; Meert 2002; Meert

and Torsvik, 2003; Li et al., 2008; Ernst et al., 2008; Hou et al., 2008; Pensonen et al.,

2012; Roberts, 2013). Roberts (2013) argues that the Columbia supercontinent

underwent minor changes rather than complete dispersal to form Rodinia.

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The reconstruction of Rodinia is partially based on linking orogenic belts of so-

called “Grenvillian” age (1.3-1.0 Ga; Fitzsimons, 2000, Hoffman 1991; Dalziel, 1991;

Moores, 1991). Although the model of Li et al. (2008) is often cited as the ‘best

reconstruction’ of Rodinia, numerous debates exist regarding paleogeographic

relationships between individual cratons (Figure 1-3; Meert, 2012; Meert and Torsvik,

2003; Piper, 2000; Torsvik et al., 1996; Li et al., 2008; Zhao et al., 2002; Pesonen et al.,

2012; Meert, 2014).

The focus of this study was to collect paleomagnetic data from mafic dykes

intruding the basement granites and gneisses of the Singhbhum craton of Peninsular

India and compare the results with the other Indian nuclei and global reconstructions.

Regional Geology

Peninsular India consists of six ancient regions: the Aravalli-Banded Gneiss

Complex; the Bundelkhand, Singhbhum, Bastar and Dharwar cratons along with the

Southern Granulite Terrain (Figure 1-4). India is typically divided into the North India

Block (NIB) and the South India Block (SIB) that are divided by the Central Indian

Tectonic Zone (CITZ). The NIB consists of the Aravalli-Banded Gneiss Complex and

Bundelkhand craton. The SIB is composed of the Singhbhum, Bastar and Dharwar

cratons along with the Southern Granulite Terrain (SGT). Within the SIB, the Bastar and

Singhbhum nuclei are separated by the Mahanadi Rift (MR) whereas the Bastar and

Dharwar craton boundary lies along the Pranhita-Godavari Rift (PG).

The exact timing of the NIB/SIB unification is contested (Mazumder, 2000; Meert

et al., 2011; Bhowmik et al., 2012; Meert and Pandit, 2015 and sources within). The

most oft-cited ages for deformation in the CITZ associated with Peninsular India

assembly are 2.5 Ga (Mazumder et al., 2000; Stein et al., 2004; 2014; Meert et al.,

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2011; Radhakrishna et al., 2013; Pradhan et al., 2012; Meert and Pandit, 2015), 1.6 Ga

(Acharyya, 2003; Meert and Pandit, 2015;) and 1.1-1.0 Ga (Acharrya, 2003; Bhowmik et

al., 2012; Pradhan et al., 2012).

Stein et al. (2004, 2014) argue that the suturing between the NIB and SIB took

place ~2.5 billion years ago, and that the younger ages reported in the region (1.6 and

1.1 Ga) represent re-working. The ~2.5 Ga for suturing of the NIB/SIB was based on the

isotopic age of the of the Malanjkhand deposit in the Sausar Mobil belt, that is argued to

have formed via subduction during NIB/SIB convergence. In 2014, Stein et al.

presented whole rock molybdenite ~2.4 Ga age in the Sausar Belt, as well as a U-Pb

titanite age of ~1.0 Ga. These ages show two distinctly different metamorphic events, in

agreement with the Stein et al. (2004) original findings; the oldest age (~2.5 Ga)

reflecting the original collision of the NIB/SIB and the younger (1.0 Ga) indicative of a

reactivation age.

Using the paleomagnetic poles and geochronology of dyke suites in the

Bundelkhand (NIB) and Dharwar (SIB), these two cratons were argued to be in close

proximity by ~1.9 Ga (Prahdan et al., 2012; Meert et al., 2011). This 1.9 Ga age does

not verify any of the suggested CITZ suture ages, but rather they suggest a possible link

in time, when the blocks may have been moving towards one another. Other authors

favor a younger model which the NIB/SIB collision along with the Marwar Block to form

“Greater India” at ~1.0 Ga, (Bhowmik et al., 2012; Pisarevsky et al., 2013). Combined

geochemical and geochronological studies on the southern margin on the CITZ, show

that NIB/SIB did not complete unification until ~1.1 to 0.9 Ga (Bhowmik et al.,2012; Roy

et al., 2006).

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There is still considerable debate on the exact timing of the NIB/SIB unification.

Before incorporating India (or parts of India) into supercontinental models, we must

ascertain the exact timing of Peninsular India’s assembly. Our study is aimed at

providing new paleomagnetic data from the northernmost craton within the SIB.

The Singhbhum craton is in the northeastern part of India (Figure 1-5). The

Singhbhum craton is bordered on the west by the Mahandi Graben, Narmada Son

Lineament, and the Indo-Gangetic plain, and to the north by the Tamar-Poropahar

Shear Zone and the Chhotanagpur Granite-Gneiss Terrain (CGGT) that forms the

eastern extension of the Central Indian Tectonic Zone (CITZ; Figure 1-5; Meert et al.,

2010; Meert and Pandit, 2015). The basement rocks of the Singhbhum craton are

subdivided into three groups: the Older Metamorphic Group (OMG; 3.6-3.5, 3.4 and 3.2

Ga), the Iron Ore Group (IOG; ~3.5Ga), and Singhbhum and related granites (3 to

3.1Ga; Mishra et al., 1999; Zhao, et al., 2003; Mondal et al., 2007; Mukhopadhyay et al.,

2008; Meert et al., 2010; Mir et al., 2011; Meert and Pandit, 2015). The Newer Dolerites

intrude all the crystalline rocks in the region (Figure 1-6; Bose, 2008, Shankar et al.,

2014, Meert et al., 2010; Meert and Pandit, 2015).

The Newer Dolerites are a suite of dykes that vary in composition from mafic to

intermediate (with rare ultramafic bodies). Mineralogically, the dykes contain augite,

olivine, andesine, labradorite with minor OPX and are considered intermediate, between

tholeiitic and alkalic dolerites (Shankar et al., 2014; Srivastava, 2000; Bose, 2008; Mir et

al, 2011; Mukhopadhyay 2001; Zhao et al., 2003; Verma and Prasad, 1974). Individual

dykes are typically 5-25 m wide, although a few small dykelets, ranging from several

inches to half a meter, often occur as offshoots from the main body (Mir et al., 2011;

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Meert et al., 2011). These larger dykes have two main crosscutting trends of NNE/SSW

and NW/SE (Figure 1-7; Meert and Pandit 2015; Meert et al. 2010; Mir et al., 2011;

Verma and Prasad 1974; Shankar et al, 2014; Mukhopadhyay 2001; Bose, 2008).

Shankar et al. (2014) argued that the NW oriented dykes are the youngest based on

cross-cutting relationships and this is confirmed by our field observations (Figure 1-8).

Until recently, geochronological control on the emplacement ages for the Newer

Dolerites was poor. Most of the earlier published ages were low-precision K-Ar and Rb-

Sr isochron determinations. The K-Ar data yielded a range of ages between 1600-950

Ma (Bose, 2008; Srivastava et al, 2000; Naqvi and Rogers, 1987; Mukhopadhyay,

2001). Additional K-Ar data studies yielded three ages of 2100 + 100Ma, 1500 + 100

Ma and 1100 + 200 Ma (Bose, 2008; and sources within). While those data indicate

Proterozoic ages for the dykes, it is unclear if they delineate three separate episodes of

intrusion.

More recently, Shankar et al. (2014, 2016) published Pb-Pb ages on two NW-SE

oriented dykes of 1766.2 + 1.1 Ma and 1764.5 + 0.9 Ma and an age of ~1.77 Ga on a

WNW trending dyke. Srivastava et al. (2016) has published a mean Pb-Pb age of ~2.25

Ga of a NE-SW trending dyke from the Kaptipada region (near the Similipal Complex)

within the Singhbhum Granite Complex (Figure 1-9). Kumar et al. (2016) has published

eight Pb-Pb dated baddeleyite ages of NNE-SSW oriented dykes throughout the

Singhbhum region, six of which gave emplacement ages of ~2.76 Ga, one at ~2.8 Ga

and one at ~2.75 Ga. These ages would represent some of the oldest dyke intrusions

into Peninsular India.

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Figure 1-1. Proterozoic supercontinent configuration of Columbia by Zhao et al. (2002;

2004), Legend: Ak = Akitkan; C = Capricorn; CA = Central Aldan; CITZ = Central Indian Tectonic Zone; E = Eburnean; F = Foxe; K = Ketilidian;KK = Kola-Karelian; Kp = Kaapvaal craton; L = Limpopo; M = Madagascar; NCB = North China Block; NQ = Nugssugtoquidian; P = Pachelma; Pe = Penokean; TA = Transantarctic;Taz = TransAmazonian; TH = Trans-Hudson; TNC = Trans North China; TT = Taltson-Thelon; SAM = South America blocks (Amazonia, Rio de la Plata); SCB = South China Block;Sf = Svecofennian; U = Ungava; V = Volhyn; WAfr = West Africa; W = Wopmay; Zm = Zimbabwe craton.

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Figure 1-2. Configuration Laurentia’s Archean cratonic nuclei (Meert, 2012).

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Figure 1-3. Reconstruction of the supercontinent Rodina (Li et al., 2008).

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Figure 1-4. Generalized geologic map of Peninsular India showing the major cratons (modified after Meert et al., 2011). The NIB (North Indian Block; blue colors) consists of the Aravalli and Bundelkhand cratons. The SIB (South Indian Block; red colors) is comprised of the Singhbhum (this study), Bastar, Dharwar, and Southern Granulite terrain. CITZ = Central Indian Tectonic Zone; GR = Godavari Rift; C = Cuddapah Basin; V = Vindhyan Basin; Ch = Chhattisgarh Basin.

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Figure 1-5. Singhbhum Craton map after Iyengar & Murthy (1982), Mista (2006) and Meert et al. (2010). IOG, Iron Ore Group; SBG-1, -2, -3, Singhbhum Granite; OMG, Older Metamorphic Group; OMTG, Older Metamorphic Tonalite Gneiss; MG, Maturbani Granite; NSO, North Singhbhum Orogen; SSZ, Singhbhum Shear Zone; PLG, Pala Lahara Gneiss.

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Figure 1-6. Summary of the cratonic elements in the Singhbhum Craton (Meert and Pandit, 2015). SG, Singhbhum Granite; MG, Mayurbanj granite; (dz), detrital zircon ages.

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Figure 1-7. Cross cutting trends of the Newer Dolerites dyke swarm, from our sampling locations.

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Figure 1-8. Cross cutting dyke relationships seen in the field (2016).

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Figure 1-9. Map of our sampling site locations. White diamonds are our sites, yellow

diamonds are the locations of the dykes dated by Shankar et al. (2014; yellow diamonds) and Srivastava et al. (2016) dated dykes in Kaptipada.

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CHAPTER 2 METHODS

Paleomagnetism

A total of 52 sites were sampled from the Newer dolerite dyke swarm in the

Singhbhum craton. Samples from sites 1-22 were collected with a portable hand drill,

and oriented hand samples were taken for sites 22-52 after the drill malfunctioned. The

location, orientation, and quality of each outcrop was recorded at every site. Whenever

possible, baked contact samples were also collected from the host rocks for analysis.

The cores collected with the gasoline-powered portable hand drill were oriented using a

Brunton geologic compass, as well as a sun-compass to correct for magnetic

interference. Hand sample blocks were oriented and marked in the field with a Brunton

geologic compass. All samples were returned to the University of Florida, where the

hand samples were re-oriented in plaster and drilled into cores with a drill press. The

cores were trimmed into symmetrical cylinders measuring 2.5 cm high and 2.5 cm in

diameter, although some cores were broken during collection and therefore vary in

volume. The natural remnant magnetization (NRM) of all samples was measured on a

Molspin spinner magnetometer or a 2-G cryogenic magnetometer, depending on the

intensity of the magnetization. From every site, two pilot samples were treated using

thermal or alternating field (AF) demagnetization. AF demagnetization was carried out

with a homebuilt demagnetizer initially, then a D-2000 AF Demagnetizer, with fields up

with 150 mT. Thermal demagnetization was carried out with an ASC-Scientific TD-48

thermal demagnetizer, with temperatures up to 600̊ C. The appropriate demagnetization

method for the remainder of the samples was chosen based on the pilot sample results.

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The primary and overprint path components were analyzed using IAPD software

(Torsvik, 2000).

Rock Magnetic Studies

Curie temperature analyses were run on several samples from every site, using a

KLY-3S susceptibility bridge. Bulk susceptibility measurements were made on at least

one sample per site or on every sample for sites with a baked contact, prior to

demagnetization. Hysteresis and coercivity and diagrams were run on a few samples

from the group. Samples were crushed into approximately two-millimeter-long pieces

and measured using a Princeton Instruments Model ##XX MircoMag vibrating sample

magnetometer (VSM). All rock magnetic studies were performed at the University of

Florida paleomagnetic laboratories.

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CHAPTER 3 RESULTS

The sampling sites of the Singhbhum craton were divided latitudinally into two

distinct groups, the “north” (Jamshedpur Group) and the “south” (Keonjhar Group),

shown in Figure 3-1. Dyke trends in both regions showed a wide variation in orientation

and NRM (Natural Remanence Magnetization) intensities. One major difference was

the magnetic mineralogy in the two regions. Although magnetite-carried directions are

present in both the North and South, a pyrrhotite-carried remanence dominated many

samples in the North. A total of six distinct paleomagnetic directions were isolated from

our dataset. The six groups identified have both normal and reverse directions. A

normal direction is defined here as a negative, upward inclination and a reverse

direction is a positive, downward inclination.

Rock Magnetic Results

Northern (Jamshedpur) Sites

There are 24 sampling sites in the Jamshedpur region, located between

22.672°N-22.408°N latitude (Figure 3-2). There are two main dyke trends found in this

region (shown in Figure 3-3). NRM intensities from these dykes range from 0.7 mA/m –

48 A/m. Representative demagnetization diagrams are shown in Figure 3-4. Thermal

demagnetization unblocking temperatures (TUB) ranged from 315-580°C (Figure 3-4)

and alternating field (AF) median destructive fields ranged from 15-80 mT, with one site

(1446) that a maximum median destructive field of 180mT. Unblocking temperatures in

this range are consistent with pyrrhotite (~330°C) and magnetite as the main

remanence carriers (~578°C; Butler., 1998), and the high applied fields are indicative of

higher coercivity minerals. The majority of the sites in the Jamshedpur region have

32

demagnetization temperatures below 400°C and AF median destructive fields below 20

mT. A few sites have remanences carried by both pyrrhotite and magnetite, or only a

high temperature component carried by magnetite (Table 3-1). Curie temperature

experiments (Figure 3-6; susceptibility vs. temperature) show decreases in susceptibility

at ~320°C (pyrrhotite) and ~560-580°C (magnetite; Figure 3-4).

Southern (Keonjhar) Sites

In the south, there are 23 sampling sites, located ~65 km south of the

Jamshedpur group sites and to the southwest of the Simlipal Basin (Figure 3-1). The

trends of these dykes are highly variable and include trends of NW-SE, N-S and NE-NW

(Figure 3-7). The dyke NRM intensities range from 0.2 mA/m – 60 A/m. The TUB range

from ~330 – 580°C and AF median destructive fields varied from 15 – 80 mT (Figure 3-

7). The unblocking temperatures are consistent with pyrrhotite and magnetite as the

main remanence carriers (Butler, 1998). Curie temperature analyses are shown in

Figure 3-8. Of the 23 sites sampled, the demagnetization behaviors show that four sites

have a remanence that is carried by pyrrhotite and six sites have directions isolated in

both pyrrhotite and magnetite (Table 3-1).

Paleomagnetic Results

There are six directional groups reported from the Singhbhum craton that are

described below, from the best to least defined groupings.

E-W Steeply Inclined Direction (Group 1)

There are four Jamshedpur and eight Keonjhar sites that account for the largest

directional group (Group 1). Group 1 has a steep E-W inclination (Table 3-2). The steep

E-W component is primarily found in the largest NE-SW trending dykes. Group 1

exhibits a dual-polarity magnetization (two sites show negative inclinations and the

33

remainder have positive inclinations). After reversing the two negatively inclined results,

Group 1 has a mean declination= 80.9° and inclination= +69.1° (α95=6.1°; k=52.06). The

reversal test (McFadden and McElhinny, 1990) showed a classification of Rc (λobs=

14.15, λcrit= 14.93). The mean paleomagnetic pole from this data set falls at 23.4°N,

125.4°E (A95= 8.8°).

At site i1427, samples were collected from the dyke (~5 m wide), the contact

between the dyke and host granite and the unbaked host. Samples from the dyke

yielded mean D=84.5°, I= +76.3° (α95=7.7°; k= 33.11). One group composed of 50-50%

dyke and granite yielded a direction of D=275°, I= +87.5°. The unbaked granite yielded

a direction at D=272.6°, I= +86.5°. The bulk susceptibility values are highest in the fine-

grained dyke interior and decreases toward the dyke/host contact and into the country

rock (Figure 3-9). Due to the steep inclinations, the baked contact test here is

inconclusive although we do note that the susceptibility profile through the dyke and

contact rocks is suggestive of baking of the host rock by the intruding dyke.

NE-SW Shallowly Inclined Directions (Group 2)

A total of six Keonjhar and three Jamshedpur vectors are in the shallow NE-SW

directional group (Table 3-3). Five of the dykes in Group 2 strike NW-SE, and four NE-

SW trending dykes also show the Group 2 direction. Of the nine sites, only one site

(1641) was isolated as a low temperature component which grouped within the shallow

NE direction; site 1641 is not included in any of the following calculations. Group 2

directions yielded a shallow SW declination= 216.7°, inclination= +3.1° (α95=20.7°, k=

20.7) and a shallow NE declination= 48.4°, inclination= -2.7° (α95=18.3, k= 18.4). After

reversing the SW direction, a mean paleomagnetic pole was calculated at 45°N, 199°E

(A95= 10°). The reversal test was indeterminate (λo = 11.69; λcrit = 24.86).

34

At site i1637, samples were collected from the dyke (~80 m wide at outcrop

location) and the contact between the dyke and host granite (Figure 3-10). Samples

from the dyke yielded mean D=53°, I= -13° (α95=9°). One sample composed of 50-

50% dyke and granite yielded a direction of D=42°, I= -10°. The baked granite yielded a

direction at D=48°, I= -13°. The unbaked granite yielded a direction of D=26°, I=

+10°.These directions show that there is more than 20° difference between the dyke

and host rock. It is possible that the shallow NE direction of the unbaked host for site

1637 is the true unmagnetized country rock signal, but given the width of the dyke, and

that the unbaked sample was collected 6 m away, it is possible that the country rock is

partially reset. It is also noted in the field observations that the dyke/host contact is

poorly defined, insinuating a deeper emplacement of the dyke. The bulk susceptibility

values are highest in the fine-grained dyke near the host rocks and decrease both

towards the interior of the dyke and out into the country rock (Figure 3-10). When

pairing the susceptibility values with the directional change from the interior dyke to the

“unbaked” sample, the data are consistent with a positive baked contact test for site

I1637.

North Intermediate Inclination Direction (Group 3)

Group 3 directions were isolated at three Jamshedpur and three Keonjhar sites

(Table 3-4). In Group 3, the dyke trends vary between NW-SE and NE-SW, although

three of the five sites trend NW-SE. Group 3 is a high temperature/ coercivity

component with the exception of site 1410; this low coercivity component was not

included in our analysis. The Group 3 direction is dual-polarity albeit with only one site

exhibiting the opposite polarity to the other four sites. After inverting the polarity of that

one site, we report a mean declination= 355°, inclination= +61° (α95=12°, k=43). The

35

reversal test was indeterminate (Ro; observed λo = 7.62, λcrit = 36.27) The mean VGP

(virtual geomagnetic pole) from this data set is 72°N, 64°E (A95= 16°).

NW-SE Shallowly Inclined Direction (Group 4)

Group 4 is a shallow NW-SE direction derived from five Jamshedpur and four

Keonjhar sites (Table 3-5). The main dyke trend of Group 4 is NW-SE, with subordinate

NE-SW trending dykes in this group. Group 4 directions are almost entirely isolated

from low coercivity/ temperature components. Group 4 has a mean declination= 309°,

inclination= 12° (α95=13°, k=34) and a shallow SE declination= 144°, inclination= -16°

(α95=21°, k=19). The mean paleomagnetic pole from Group 4 is 45°N, 344°E (A95= 9°).

The reversal test was indeterminate (λo = 18.01, λcrit = 23.83).

E-W Intermediate Inclination Directions (Group 5 and 6)

The remaining two directional groups exhibit moderately steep inclinations

oriented along the E-W plane. These directions are isolated in both NE-SW and NW-

SE trending dykes. The group 5 dual-polarity direction is Dec= 257°, Inc= +37° and the

group 6 dual-polarity direction is Dec=88° Inc=+41°. Since both of these groups were

isolated in only a few sites, we do not attempt to evaluate their significance for plate

reconstructions.

36

Figure 3-1. Map showing all sampling sites in the Singhbhum craton.

Jamshedpur

Keonjhar

37

Figure 3-2. Geological map of the Singhbhum crustal provinces (after Bose, 1994; Bose et al. 2009) to the north of the Singhbhum nucleus. Our study sites oriented as blue strike lines; 1 – Singhbhum granite platform. 2 - Banded iron formation bearing supracrustals. 3 - Proterozoic volcanosedimentary basin (Proterozoic Singhbhum Basin). DB = Dhanjori basinal domain of PSB. 4 - Dalma midbasinal volcanic belt. 5 - Mayurbhanj granite (MG). 6 - Younger sedimentary basin, Kolhan Basin (KB). 7 - Northern fringe of Jagannathpur basalt (JB). 8 - Chotanagpur highlands(granite gneiss, granulites and migmatites). 9 - Antiformal / Synformal fold. RK = Rakha mines TN = Tatanagar, CH=Chaibasa, CP = Chakradharpur.

1 2 3 4 5 6 7 8 9

38

Figure 3-3. Rose diagram depicting only dyke trends observed in the North study area.

39

Figure 3-4. Orthogonal vector plots, equal area stereonets and thermal demagnetization

behavior for the Jamshedpur low temperature/coercivity component dykes of the Singhbhum craton. These plots show typical characteristic remanent magnetization directions, where solid (open) circles represent projections on the horizontal (vertical) plane in the orthogonal plots while up (down) pointingpaleomagnetic directions are indicated by open (closed) circles in the stereoplots.

40

41

Figure 3-5. Orthogonal vector plots, equal area stereonets and thermal demagnetization behavior for the Jamshedpur high temperature/coercivity component dykes of the Singhbhum craton. These plots show typical characteristic remanent magnetization directions, where solid (open) circles represent projections on the horizontal (vertical) plane in the orthogonal plots while up (down) pointing paleomagnetic directions areindicated by open (closed) circles in the stereoplots.

42

43

Figure 3-6. Curie Temperature analysis of the Jamshedpur samples. Here both heating (Tch) and cooling (Tcc) curves are shown with the Curie temperature analyses.

44

45

Figure 3-7. Rose diagram depicting only the dyke trends observed in the South study

area.

46

Figure3-8. Orthogonal vector plots, equal area stereonets and thermal demagnetization

behavior for the Keonjhar region of the Singhbhum craton showing typical characteristic remanent magnetization directions. Solid (open) circles represent projections on the horizontal (vertical) plane in the orthogonal plots while up (down) pointing paleomagnetic directions areindicated by open (closed) circles in the stereoplots

47

.

48

Figure 3-9. Curie Temperature analysis of the Keonjhar samples. Here both heating

(Tch) and cooling (Tcc) curves are shown with the Curie temperature analyses.

49

Figure 3-10. Log bulk susceptibility versus distance plot of site i1427 contacts.

50

Figure 3-11. Paleomagnetic results from 1637 dyke and country rock, including a) plot

of log susceptibility vs. distance from dyke contact; b) thermal demagnetization diagram and stereoplot of vectors for the central dyke; c) thermal demagnetization diagram and stereoplot of vectors for the dyke margin; d) thermal demagnetization diagram and stereoplot of vectors for the dyke/granite hydrid; e) thermal demagnetization diagram and stereoplot of vectors for the baked granite; f) alternating field demagnetization diagram and stereoplot of vectors for the unbaked granite.

51

Table 3-1. All 2014 Paleomagnetic Results

Site Slat (°N)

Slong (°E)

Location Trend N D (°) I (°) α95 k Plat (°N) Plong (°E)

3 LF 22.623 86.118 Jamshedpur 45-225 5 23.3 -43.2 15 21.0 -37.2 59.4

4 LF 22.614 86.010 Jamshedpur 130-310 8 278.8 -16.5 8.8 31.1 -4.8 164.8

5 LF 22.608 86.079 Jamshedpur 130-310 6 133.3 1.2 6.7 102.4 -21.2 166.1

5 HF 22.608 86.079 Jamshedpur 130-310 12 126.7 -18.8 11.3 14.5 37.5 350.9

6 LF 22.634 86.078 Jamshedpur 30-210 8 192.1 -20.9 4.5 131.5 74.1 222.1

7dyke1 LF 22.632 86.061 Jamshedpur 20-200 4 88.3 34.4 13.4 33.4 8.7 159.7

7dyke2 LF 22.632 86.061 Jamshedpur 20-200 3 256.5 41.5 16.1 33.4 -2.4 23.2

8 LF 22.632 86.060 Jamshedpur 130-310 5 314.2 3.4 8.5 63.8 40.9 337.5

8 HF 22.632 86.060 Jamshedpur 130-310 5 334.8 57 13.3 33.9 63.7 36.5

9 HF 22.621 86.005 Jamshedpur 140-320 6 16 74.1 6.5 86.0 50.7 98.4

10 LF 22.408 86.145 Jamshedpur 150-330 9 344.9 56.8 15.8 9.4 70.2 48.6

10 HF 22.408 86.145 Jamshedpur 150-330 9 248.8 26.6 14.5 13.6 -13.4 17.8

11 LF 22.572 86.148 Jamshedpur 10-190 8 162.8 18.1 8.4 38.2 -54 115.9

12 22.572 86.148 Jamshedpur 150-330

Scatter

13 LF 22.405 86.148 Jamshedpur 40-220 8 109.6 57.5 4.4 122.7 -0.5 135

14 LF 22.548 86.159 Jamshedpur 35-215

Scatter

14contact 22.548 86.159 Jamshedpur 35-215 6 236.7 68 10.8 39.7 -1.2 54.5

15 LF 22.640 86.019 Jamshedpur 0-180

Scatter

16 HF 22.672 85.969 Jamshedpur 140-320

Scatter

17 HF 22.583 85.910 Jamshedpur 40-220 5 84.5 58.1 6.9 95.6 18 141.6

18 LF 22.619 85.981 Jamshedpur 40-220 3 28.6 -10.5 17 53.5 -50.5 37.5

19 HF 21.567 85.697 Keonjhar 130-310 6 227.2 -4.7 10.7 40.2 40.3 192.8

20 HF 21.567 85.697 Keonjhar 20-200 7 58.5 11.5 10.9 26.9 31.4 183.2

22 21.517 85.821 Keonjhar 40-220

Scatter

22a LT 21.517 85.821 Keonjhar 40-220 6 102.3 17.6 4 116.5 -7.9 162.8

22a HT 21.517 85.821 Keonjhar 40-220 6 94.3 41.8 9 24.4 4.9 151.8

23a LT 21.515 85.822 Keonjhar 25-205 8 167.2 -21.9 8.5 43.6 74.1 318.2

23ab HT 21.515 85.822 Keonjhar 25-205 9 174.8 61.4 7 48.3 -25.8 90.1

26 HT 21.568 85.651 Keonjhar 140-320 7 228.8 68.3 7.7 45.8 -5.4 57.6

27 HF 21.551 85.662 Keonjhar 140-320 10 84.5 76.3 7.7 33.1 21.7 113.7

27Baked 21.551 85.662 Keonjhar 140-320 4 275.4 87.5 14.3 42.3 21.9 80.3

27Unbaked 21.551 85.662 Keonjhar 140-320 11 272.6 86.5 4.5 239.4 31.3 70.6

28a 21.509 85.677 Keonjhar 150-330

Scatter

29 LF 21.404 85.740 Keonjhar 25-205 9 155 4.1 8 42.8 -56.1 135

52

Table 3-1. Continued

Site Slat (°N)

Slong (°E)

Location Trend N D (°) I (°) α95 k Plat (°N) Plong (°E)

29 HF 21.404 85.740 Keonjhar 25-205 8 46 69 2 972.0 43.1 122.6

30 HF 21.333 85.287 Keonjhar 170-350 15 206.3 -6.8 5.4 51.0 58.8 206.7

31a LF 21.229 85.759 Keonjhar 165-345 3 35.7 5.6 11.9 60.5 50.7 199.8

31b LF 21.229 85.759 Keonjhar 165-345 8 143.7 -29.8 6.6 61.9 55.3 354.4

32b LF 21.317 85.817 Keonjhar 165-345 5 297 62.7 5 76.0 33.8 35.4

32a HF 21.317 85.817 Keonjhar 165-345 5 335.5 83.7 8.9 57.4 32.5 79.7

33 LF 21.643 85.651 Keonjhar 0-180 3 105.9 66.6 10.9 71.8 6.4 125

33contact 21.643 85.651 Keonjhar 0-180 6 87.9 51.5 11.6 34.2 13 145.9

34 HF 21.643 85.651 Keonjhar 10-190 1 76.4 73.4 5.5 - 25.4 119.1

35 HF 21.553 86.016 Keonjhar 120-300 11 221.4 -77.7 3.6 136.2 38 104.6

35c_contact 21.553 86.016 Keonjhar 120-300 3 223.5 49.2 1.4 4180.3 -23.6 45.5

35e_contactgr 21.553 86.016 Keonjhar 120-300 2 98.2 -42.6 5.2 557.3 15.9 16.8

36LF 21.553 86.016 Keonjhar 140-320 3 312.1 19.1 9 105.1 42.6 359.5

36HF 21.553 86.016 Keonjhar 140-320 4 261.5 -45.6 7.6 79.1 16.8 153

36unbake 21.553 86.016 Keonjhar 140-320 5 89.1 -68.7 8.4 83.9 16.3 46.2

37 HF 21.553 86.016 Keonjhar 55-235 7 56.7 -51.7 2.8 344.1 -13.6 38.4

38 HF 21.553 86.016 Keonjhar 55-235 4 94 60.5 2.7 805.6 11.2 134.7

39 HF 21.553 86.016 Keonjhar 25-205 12 343.7 -78.1 4.4 89.6 -0.5 91.3

40 21.553 86.016 Keonjhar 10-190 2 308.5 -57.3 10 620.0 -13.4 124.4

41 HF 21.829 85.847 Keonjhar 25-205 7 236.4 -40.9 5.3 131.6 38.3 162.6

42 HF 21.832 85.861 Keonjhar 20-200 5 112.6 -45.1 4.8 252.9 29.1 15.1

42 LF 21.832 85.861 Keonjhar 20-200 6 358.1 23.1 3.4 397.7 80 276.4

43 LF 21.845 85.895 Keonjhar 10-190 5 344.4 30.5 9 46.3 74.3 338.4

44 LF 21.779 85.563 Keonjhar 30-210 5 93 78.6 10.9 38.7 19 108.8

45 HF 22.530 85.866 Jamshedpur 20-220 6 17.1 46.9 10.6 28.3 73.6 152.5

46 LF 22.536 85.904 Jamshedpur 20-200 7 299.6 14.4 6.4 89.0 30.1 351.3

46 HF 22.536 85.904 Jamshedpur 20-200 8 214.9 26.6 2 733.5 -39.9 39.5

47 LF 22.559 85.876 Jamshedpur 40-220 4 10 40 3.9 238.7 80.8 172.7

48 HF 22.559 85.876 Jamshedpur 40-220 6 351 50.7 3.1 315.6 78.1 45.7

49 LF 22.618 85.999 Jamshedpur 10-190 13 66.3 -6.6 2 378.6 -20.4 8.8

50 HF 22.423 86.078 Jamshedpur 40-220 9 228.3 -67 5.9 67.1 43.5 127.9

51 HF 22.411 86.0751 Jamshedpur 130-310 8 84.3 59.8 4.9 98.9 18.5 138.8

52ac LF 22.613 86.1837 Jamshedpur 40-220 8 84.8 -40.1 5.1 103.6 4.1 19.2

52b LF 22.613 86.1837 Jamshedpur 40-220 3 149 -18.9 91 101.9 57.6 337.4

53

Notes: Slat=site latitude, Slong=site longitude, Location= sampling group N=number of samples, Dec=declination, Inc=inclination, α95=cone of 95% confidence about the mean direction, k=kappa precision parameter (Fisher, 1953), Plat = pole latitude, Plong = pole longitude.

54

Table 3-2. Paleomagnetic results from Group 1

Site Slat (°N) Slong (°E) Trend N D (°) I (°) α95 k Plat (°N) Plong (°E) Dp Dm

13 LF 22.405 86.148 40-220 8 109.6 57.5 4.4 123 -0.5 135 4.7 6.4

33 LF 21.643 85.651 0-180 3 105.9 66.6 10.9 72 6.4 125 14.8 18

44 LF 21.779 85.563 30-210 5 93 78.6 10.9 39 19 108.8 19.5 20.6

17 HF 22.583 85.910 40-220 5 84.5 58.1 6.9 96 18 141.6 7.5 10.2

27 HF 21.551 85.662 140-320 10 84.5 76.3 7.7 33 21.7 113.7 13.2 14.2

29 HF 21.404 85.740 25-205 9 46 69 2 972 43.1 122.6 2.9 3.4

34 HF 21.643 85.651 10-190 1 76.4 73.4 5.5 - 25.4 119.1 8.8 9.9

35 HF 21.553 86.016 120-300 11 221.4 -77.7 3.6 136 38 104.6 6.3 6.8

38 HF 21.553 86.016 55-235 4 94 60.5 2.7 806 11.2 134.7 3.1 4.1

50 HF 22.423 86.078 40-220 9 228.3 -67 5.9 67 43.5 127.9 8.1 9.8

51 HF 22.4112 86.0751 130-310 8 84.3 59.8 4.9 99 18.5 138.8 5.6 7.4

1641 HF 21.553 86.017 130-310 10 65 68 5 110 32.2 128.33 7 8.4

Group 1 Mean

80.9 69.1 6.1 52 23.4 125.4 A95= 8.8°

Notes: Slat=site latitude, Slong=site longitude, N=number of samples, Dec=declination, Inc=inclination, α95=cone of 95% confidence about the mean direction, k=kappa precision parameter (Fisher, 1953), Plat = pole latitude, Plong = pole longitude.

55

Table 3-3. Paleomagnetic results from Group 2. Site Slat (°N) Slong (°E) Trend N D (°) I (°) α9

5 k Plat

(°N) Plong (°E)

Dp Dm

18 LF 22.619 85.981 40-220 3 28.6 -10.5

17 54 -50.5 37.5 8.7 17.2

31a LF 21.229 85.759 165-345 3 35.7 5.6 12 60 50.7 199.8 6 11.9

49 LF 22.618 85.999 10-190 13 66.3 -6.6 2 379

-20.4 8.8 1 2

1641 LF* 21.553 86.017 130-310 5 35 9 20 16 52 197.6 10.2

20.2

19 HF 21.567 85.697 130-310 6 227.2 -4.7 11 40 40.3 192.8 5.4 10.7

20 HF 21.567 85.697 20-200 7 58.5 11.5

11 27 31.4 183.2 5.6 11.1

30 HF 21.333 85.287 170-350 15 206.3 -6.8 5 51 58.8 206.7 2.7 5.4

1637 21.593 85.726 120-300 6 53 -13 9 60 -30.9 18.1 4.7 9.2

i498 22.556 86.152 40-220 7 218 -2.2 7 7 47.3 201 3.5 7

Group 3 Mean 9 43.2 -2.9 12 20 45.4 198.7 A95=

8.7° Notes: Slat=site latitude, Slong=site longitude, N=number of samples, Dec=declination, Inc=inclination, α95=cone of 95% confidence about the mean direction, k=kappa precision parameter (Fisher, 1953), Plat = pole latitude, Plong = pole longitude, *1641 LF was excluded from all group calculations.

56

Table 3-4. Paleomagnetic results from Group 3. Site Slat (°N) Slong (°E) Trend N D (°) I (°) α95 k Plat (°N) Plong (°E) Dp Dm

10 LF 22.408 86.145 150-330 9 344.9 56.8 15.8 9 70.2 48.6 16.6 22.9

1648 LF 21.554 86.018 240-60 7 8 53 10 36 76.1 114.8 9.6 13.8

8 HF 22.632 86.060 130-310 5 334.8 57 13.3 34 63.7 36.5 14.1 19.3

48 HF 22.559 85.876 40-220 6 351 50.7 3.1 316 78.1 45.7 2.8 4.2

1639 HF 21.566 85.705 315-135 5 172 -67 6 156 61.2 8.2 8.2 9.9

Group 2 Mean

350.4 57.4 8.7 78 71.7 61 A95= 11.5°

Notes: Slat=site latitude, Slong=site longitude, N=number of samples, Dec=declination, Inc=inclination, α95=cone of 95% confidence about the mean direction, k=kappa precision parameter (Fisher, 1953), Plat = pole latitude, Plong = pole longitude.

57

Table 3-5. Paleomagnetic results from Group 4.

Site Slat (°N)

Slong (°E)

Trend N D (°) I (°) α95 k Plat (°N)

Plong (°E)

Dp Dm

8 LF 22.632 86.060

130-310

5 314.2

3.4 8.5 64 40.9 337.5 4.3 8.5

29 LF 21.404 85.740 25-205 9 155 4.1 8 43 -56.1 135 4 8

31b LF

21.229 85.759 165-345

8 143.7

-29.8

6.6 62 55.3 354.4 4.1 7.3

36 LF 21.553 86.016

140-320

3 312.1

19.1

9 105

42.6 359.5 4.9 9.4

46 LF 22.536 85.904

20-200 7 299.6

14.4

6.4 89 30.1 351.3 3.4 6.6

52b LF

22.6135 86.1837

40-220 3 149 -18.9

91 102

57.6 337.4 4.9 9.5

5 HF 22.608 86.079

130-310

12

126.7

-18.8

11.3

15 37.5 350.9 6.1 11.8

1636 21.592 85.725

9 321 24 9 32 51.7 348.6 5.1 9.6

i499 22.548 86.154 130-310

9 299 0 12 18 26.6 344.2 6 12

Group 4 Mean

315.4

14.1

10.9 23 44.7 344.1 A95= 9°

Notes: Slat=site latitude, Slong=site longitude, N=number of samples, Dec=declination, Inc=inclination, α95=cone of 95% confidence about the mean direction, k=kappa precision parameter (Fisher, 1953), Plat = pole latitude, Plong = pole longitude.

58

CHAPTER 4 DISCUSSION

The position of the Singhbhum craton within Peninsular India was poorly

constrained due to the paucity of high-quality paleomagnetic data. The purpose of this

study was to obtain new paleomagnetic data from dated mafic dykes in the Singhbhum

craton and use those data to test models of India assembly and to evaluate the position

of the Singhbhum craton in global reconstructions.

Our study was hindered by the fact that many dykes carried a pyrrhotite-

dominated remanence. A low temperature/coercivity component, most likely pyrrhotite,

was most commonly found in the Jamshedpur group, but several sites in the Keonjhar

group are also dominated by pyrrhotite. This low temperature component was noted in

previous paleomagnetic studies on the Newer Dolerites from the northern part of

Singhbhum craton (Jamshedpur region; Verma and Prasad, 1974). The authors

interpreted the first pole (67°N, 46°W, a95=16°) as 1600-910 Ma in age whereas, the

second pole (29.5°N, 94°E, a95=16.5°) and the third pole (28°N, 56°W, a95=13°) were

classified as generally Precambrian in age due to the lack of age constraints at the time.

In a paleomagnetic study of the Sukinda Chromites, near the southern margin of

the Singhbhum craton, Kumar and Bhalla (1984) used thermal and AF demagnetization

and reported that the majority of their samples became scattered after they were heated

above 300°C and had a sharp decrease in intensity by 20 mT. They reported a pole

direction of 47 °N, 220°E and assigned this pole an age of 1800 + 200 Ma.

Verma and Prasad (1974) performed petrographic studies, in which they found

alteration of magnetic minerals, specifically to Ti-rich Leucoxene, present in their

samples and attributed this alteration to the possibility of low grade regional

59

metamorphism event of a younger age. Since the northern edge of the Singhbhum

craton is located near the CITZ, there is a possibility that the pyrrhotite-rich sampling

sites were locally reheated and therefore remagnetized. In order reset pyrrhotite’s

magnetic alignment, the metamorphism would have to be above ~320°C.

There are numerous dyke trends found in the Newer Dolerites. These include the

more common NW-SE and NE-SW trends along with fewer N-S trending dykes. Dyke

orientations varied in both the Jamshedpur and Keonjhar regions; however, we

identified relationships between dyke trends and directional groups in our study. We

believe that the larger dykes can be used with more confidence when comparing dyke

trends to directional groups and ages.

~1.77 Ga Dykes

In spite of the fact that dyke trends are not always diagnostic of their ages, we do

believe that we can speculatively correlate some of our directional groups to specifically

oriented geochronologically dated dykes in the Singhbhum craton. Shankar et al. (2014;

2016) reported several precise Pb-Pb ages for the some of the larger WNW trending

dykes (Figure 4-1). Sites i1636 and i1637 were collected along a reservoir where the

1765 Ma WNW trending dyke outcropped (Figure 4-2). Each of the sampled sites

yielded different directional components; site i1636 had two components, yielding a

lower temperature/coercivity direction mean declination= 321°, inclination= +24°

(α95=9°) and a higher temperature component with a mean declination= 005°,

inclination= -82° (α95=7°), and site 1637 had a mean 53°, inclination= -13° (α95=9°).

This same WNW dyke was reported to have a NNW/SSE shallow inclination

direction for 10 sites in the Singhbhum, with a mean declination= 329°, inclination= -27°

(α95= 11°; Shankar et al., 2016). Shankar et al. (2016) reported a high coercivity, stable

60

vector component for this NW-SE directed shallow paleomagnetic direction, with

magnetite as the dominant magnetic carrier. This contradicts our own findings for the

shallow NW-SE directional group wherein the direction is isolated almost entirely within

low coercivity/temperature intervals. In our thermal and AF demagnetization of site

i1636, we found large drop in intensity by 325°C and 10 mT respectively, indicative of a

low coercivity/temperature component, such as pyrrhotite. We have a paleomagnetic

pole position of 44.7°N, 344.1°E (A95= 9°) for the shallow NW-SE group and Shankar et

al. (2016) reported a pole position of 43.4°N, 308.7°E for their directions (Figure 4-3).

There is a longitudinal difference of ~ 40° between the two poles. This variance could

be due to the fact that we sampled a larger area and sites from both regions

(Jamshedpur and Keonjhar) are included in our pole position. The Jamshedpur sites

consisted of primarily low coercivity/temperature components, which is how we defined

this shallow NW-SE direction and could be attributed to the variance in the two pole

positions.

At Site i1637, we have identified a high temperature/ coercivity component

carried by magnetite with a shallow NE-SW direction. The NE-SW direction reported in

this study is a stable, primarily high temperature/coercivity component, with a

paleomagnetic pole position calculated at 45°N, 199°E (A95= 10°). Our pole is similar to

that of Kumar and Bhalla (1984) for the Sukinda Chromites (47 °N, 220°E; A95=6.5°)

and the pole of Das et al. (1995) for banded hematite jasper rocks (37°N, 195°E;

A95=17°). The three poles overlap within their errors and are shown in Figure 4-4.

Kumar and Bhalla (1984) assign an age for their pole that falls, broady, within error

(1830+200 Ma) to ours. In contrast, Das et al. (1995) assigned a much older age to

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their pole of between 2600-2900 Ma. Kumar and Bhalla (1984) performed a fold test

on the Chromite ore deposit, which their paleomagnetic data yielded a pre-folding

remanence and the age of this pole was obtained by comparing their pole position to

the Gwalior Traps. The older age (Das et al., 1995; 2600-2900 Ma) is from the

sedimentary banded iron formation within the Iron Ore Group, and thought to be a pre-

folding age, although the field tests were inconclusive. It is possible that the 2600-2900

Ma age is an older detrital age, that the paleomagnetic signal is a younger direction

and/or the younger age is a remagnetized age.

~2.2 Ga Dykes

Srivastava et al. (2016) reported a mean Pb-Pb age of ~2.25 Ga for NE-SW

trending dykes in the Kaptipada region of the Singhbhum craton (Figure 3-1). The

reported age comes from dykes to the east of our southern study area. In our study, we

isolated a stable paleomagnetic direction in the NE-SW trending dykes. Our steeply

inclined E-W group, has a pole position of 22° N, 126 °E (A95= 9°) which is similar to the

2.21 Ga pole position of 31°N, 121°E (A95= 11.5°) determined from similar-aged dykes

in the Dharwar craton (Belica et al., 2014; Figure 4-5). Although contact tests were

inconclusive, the steep E-W direction yielded a Rc classification for the reversal test,

which increases the likelihood that this is a stable direction for at least one

emplacement pulse of the Newer Dolerites.

North Group Direction

The last directional group reported is a northerly direction with an intermediate

inclination that yields a mean VGP of 72°N, 64°E (A95= 16°). This pole position is similar

to two previously reported pole directions in India; the 750 Ma north India Malani pole

(68°N, 73°E, A95=9°; Meert et al., 2013) and the 2.18 Ga south India Dharwar pole

62

position (68°N, 85°E, A95=18°; Belica et al., 2014). There are no similar ages that are

reported from the Singhbhum craton; therefore we cannot definitively make a correlation

to between the reported poles and our pole. The reversal test was indeterminant, but

the moderately inclined north group is a primarily high coercivity/temperature directional

group, so we believe that this direction may be primary.

Global Reconstructions

Here we report on two ages of dyke emplacement for the Singhbhum craton.

From our study, we have paleomagnetic evidence that the Singhbhum and Dharwar

cratons were likely in close proximity to one another as early as ~2.2 Ga (Figure 4-5). If

this is the case, that would imply that SIB cratons were in close proximity at this interval,

giving better constraints on the SIB unification age. The debate on when the SIB nuclei

(Singhbhum, Bastar and Dharwar) came together has been poorly defined due to the

lack of paleomagnetic constraints, specifically in the Singhbhum craton. In the Dharwar

and Bastar, there are similarly reported ages (~1.8-1.9 Ga) and directions, implying

proximal positions of the two nuclei at this time (Meert et al., 2011). With the Bastar

craton located in between the Singhbhum and the Dharwar, we now can infer that the

entire SIB was likely unified, or at least neighbors, by ~1.8-1.9 Ga. We can infer this

relationship with some confidence, due to the similar localities of the Singhbhum and

Dharwar paleomagnetic poles at ~2.2Ga (Belica et al., 2014; Srivastava et al., 2016).

The amalgamation timing of the SIB, and ultimately Peninsular India is important for

global scale reconstructions. Specifically, the importance lies in whether the NIB/SIB

were unified or separate; if the later, then the specific cratons of India need to be

clarified when making a reconstruction.

63

As described above, there is consistent NE-SW mean direction seen in the

Singhbhum, although the associated ages vary from 2900-1765 Ma (Shankar et al.,

2014; Das et al., 1995; Verma and Prasad, 1974). This wide range of ages could be due

to the lack of robust dating techniques at the time the earlier papers published (1976;

1995), or it could infer a possible remagnetization present. We believe that the precise

Pb-Pb age of 1765 Ma (Shankar et al., 2014;2016) to be the most robust age of the

group, and are therefore able to give a location of the Singhbhum craton at this interval.

The Bundelkhand craton has a pole positon and age, neighboring the Singhbhum

~1.77 Ga pole (15.4°N, 173°E; 1780 Ma; Pradhan et al., 2010). Although the age

constraints on the Bundelkhand pole are less defined, and there is a variance between

these pole positions, the similarities of the two poles could imply a connection between

the NIB/SIB at this time interval (~1.78-~1.77 Ga). We can also correlate the

Singhbhum to other cratons globally at this interval (~1.77Ga). These correlations are

important for gaining a better understanding of the formation of Proterozoic

supercontinents, like Columbia, especially since the location of India is still contested at

this time. The current Proterozoic reconstructions show India near a variety of cratons

including North China, East Antarctica, Australia, Baltica and Amazonia. Here we

compare the location of the Singhbhum craton to North China, Baltica, Amazonia,

Laurentia and Rio de la Plata, due to the availability of poles during this time, ~1.77 Ga

(Table 4-1; Figure 4-6).

For this reconstruction, the position of the Fennoscandian component of Baltica

comes from Pisarevsky and Bylund (2010) who presented a paleomagnetic pole for the

Smaland intrusives in Fennoscandia at 1778 Ma, with a primary signal that was verified

64

via a positive baked contact test. The Laurentia paleomagnetic pole was obtained in the

Cleaver Dykes, at 1740 Ma (Irving et al., 2004). There were also contact tests

performed in this dyke suit, which yielded a post-orogenic overprint, consistent with the

Hudson orogeny. The Rio de la Playa paleopole was obtained from the Florida dykes

(Teixeira et al., 2013), at 1790 Ma, but has a few different possible craton positons. The

Colider volcanics pole from southwest Amazonia are shown (Bispos-Santos, 2012),

carried by a Ti-poor characteristic component, which is thought to be a primary

remanence from petrographic and magnetic minerology analysis, with an age of 1785

Ma. The last craton shown is North China, represented by the Yinshan dykes

paleomagnetic pole (1780 Ma; Xu et al., 2014), with contact tests performed on two

Yinshan dykes, which were intruded by a younger dyke, and demonstrated the Yishan

dykes to be older than ~1320 Ma.

Our reconstruction of ~1.77 Ga, shows some similarities to previously published

Proterozoic reconstructions (Zhao et al., 2002; 2004). Most noticeable is the connection

of North China to India, which was originally proposed based on orogenic belts (Zhao et

al., 2002). Srivastava et al. (2016) suggests that the North China, Baltica, Rio de la

Playa and Indian cratons were adjacent to one another, due to the possible remanence

of a large igneous province at ~1.77Ga. From our reconstruction, there is a connection

present between North China and Baltica, which could support the hypothesis of a LIP

during Columbia, although Rio de la Playa is not included in this connection. Rio de la

Playa is instead located near Amazonia, as mentioned in Teixeira et al. (2013) as one of

the possible connections. The issue associated with our reconstruction is the lack of

available poles at ~1.77 Ga, and with only a few cratons available, we cannot

65

completely understand the amalgamation of this Proterozoic formation, or assess it at

its entirety.

66

Figure 4-1. Shankar et al. (2014) 206Pb/207Pb ages from five baddeleyite fractions from the Newer Dolerite swarm. Error bars represent 95% confidence limit of measurements.

67

Figure 4-2. Sampling locations of 1636 (red star) and 1637 (yellow star), of the 1765 Ma

WNW trending dyke.

68

Figure 4-3. Comparison of the Shankar et al. (2016) and this study pole position for the

shallow NW-SE direction.

69

Figure 4-4. Comparison of shallow NE-SE direction poles observed in the Singhbhum

craton. Das et al. (1995; blue), Kumar and Bhalla (1984; yellow) and this study (pink) poles are shown which have age ranges from 2900-1765 Ma.

70

Figure 4-5. Comparison of the Belica et al. (2014) and this study’s pole position for the ~2.2 Ga direction.

Belica et al. 2014

This study

Dharwar

Singhbhum

71

Figure 4-6. ~1.77 Ga paleogeographic reconstruction. Outlines are the Amazonia, North China, India, Baltica, Laurentia and Rio de la Playa cratons in a possible configuration during the supercontinent Columbia.

72

Table 4-1. Paleomagnetic poles used in ~1.77 Ga Continental Reconstruction.

Pole Name Cont./Craton

Plat (°N)

Plong (°E) A95 Age Reference

Smaland Intrusives

Baltica 46 183 8 1778 Pisarevsky and Bylund, 2010

Yishan Dykes North China 42 246 4 1780 Halls et al., 2000; Piper et al., 2011

Newer Dolerites

India 44 199 10 1765 This Study

Florida Dykes Rio de la Plata

78 342 10 1790 Texeira et al., 2013

Colider Volcanics

Amazonia 63 119 11 1785 Bispos-Santos et al., 2008

Cleaver Dykes Laurentia 19 276 9 1740 Irving et al., 2004

73

CHAPTER 5 CONCLUSIONS

Paleomagnetic studies are necessary in understanding the cyclicity of

supercontinent formation and dispersal. Although there has been an increase in such

studies, Proterozoic supercontinents are still controversial in geometry and make up.

The addition of paleomagnetic poles will help constrain landmass amagalmation on both

the small (i.e. cratonic) and global (i.e. supercontinental) scale. Our reconstruction at

~1.77 Ga shows that the exact make up of Columbia is variable and therefore complex,

but with increasing availability of paleomagnetic poles, this supercontinent assembly is

becoming better defined. Our main conclusions from our study are listed below.

First, in the Singhbhum craton, specifically the North (Jamshedpur region) but

also in the South (Keonjhar) there is a dominant low temperature/coercivity remanence.

This remanence was seen is samples which were demagnetized thermally to 350°C and

had AF median fields of 20 mT, which we have identified as pyrrhotite. This magnetic

carrier can be problematic, because the north margin of the Singhbhum craton is a part

of the CITZ and if this region had been activated during the NIB/SIB collision, causing

regional metamorphism, that could have remagnetized the magnetic signal to a younger

direction.

Second, the combined ~2.2 Ga age (Srivastava et al., 2016) of the NE trending

dykes, with our paleomagnetic pole, gives constraints on a unification age of the SIB,

due to the similar paleomagnetic poles and ages seen in the Dharwar and Singhbhum.

There has yet to be a similar age identified in the Bastar craton, but due to the

positioning of the nuclei, it is likely all three cratons were in close proximity ~2.2Ga.

74

Third, we present a paleomagnetic pole for a dated WNW trending dyke of 1765

Ma, which is also presented in previous studies from the Singhbhum (Das et al., 1995;

Kumar and Bhalla, 1984). This combined pole and age can be used to test possible

Columbia configurations. Our reconstruction agrees with some previously proposed

connections, such as India/North China, but there are still issues with the configuration.

Specifically, at ~1.77 there are few poles to adequately test a complete reconstruction,

that consists of the majority of the landmass present in that interval.

Last, we present a mean VGP for the Singhbhum craton which has no

geochronological constraints, but does match with two other poles (the 750 Ma Malani

and 2.18 Ga Dharwar) seen in Greater India. Since we do not have any age constrains

on our pole, we cannot evaluate this position to a greater extent.

75

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BIOGRAPHICAL SKETCH

Karastin Daun Katusin was born in northeast Ohio, and continued to live in the

region until she received her Bachelor of Science in geology from the University of

Akron in May 2014. She completed her master’s degree at the University of Florida in

August 2017. Her future goals are to move to the western U.S. and pursue a career in

field geology and teaching.