Botala Boloso, JorgeSummer Field SchoolJune 24, 2007

Mining Considerations After Summitville, CO.Environmental Concerns

Introduction:

In this paper I present the results from our study of the water chemistry at

Summitville mine area, CO, located 10 km north-west of platoro. In addition, these

results reveal that the water quality at Summerville is affected by two primary factors: a)

the amount of discharge in the Alamosa River and its affluences; and b) the proximity

with respect to the mine area. On the other hand, rock chemistry analysis along the

different locations where our water sample were collected was necessary to determine

whether we were more proximal (argillic) or distal (propylithic) to concentrated

hydrothermal fluid flow. Since the chemistry of these rocks also affect the acidity of the

water.

Regional Geology

The regional geology of the Western US is identified along with several orogenic

systems related to the Laramite Orogeny, which is defined as an arc bar of very shallow

slab angle resulted in the uplift and faulting (700-40 Ma). The Laramite Orogeny is

characterized by a westward migration originated from slap dilamination (~40 Ma).

Laramite uplift extends from southern Canada to Mexico. In addition, sedimentary unit

along the Laramite orogeny are identified with steeply dipping angles. Some formations

identified with the Laramite orogeny include:

a) Hurfano Butte (25.2 Ma), located one mile east of the exit 59 on I-25. It represent

the easternmost tertiary intrusive in the US. In addition, orogenic system is related to the

tertiary extension of the Rio Grande Rift. Also, the rocks we observed at this location

were primarily felsic intrusive igneous rocks related to two main phases: nepheline gabro

and diorite. Furthermore, we observed the baking of the Pierre shale, which is an

indicative of a contact metamorphism between the minette and the shale.

b) Spanish Peak - East and the West Spanish Peak - (22-25 Ma), located 3 miles

west of Lavita, CO. Characteristic about this peak is the series of radio dikes that emanate

from the central part of these peaks and extend to the NW. Also, one of the mysteries

related to the Spanish Peak is the Gormer Butte, which is and extrusive body of rocks in

the vicinity of the Spanish peak while the top of the Spanish peak itself is intrusive. The

Gormer Butte extrusive body is the same age as the Spanish Peak.

c) Cuchara Formation – It is a series of Tertiary conglomerate related to the

Laramite Orogeny.

d) Sun Grays – Represents a series of Precambrian units that originated from the

Laramite orogeny. Most remarkable able this formation is the series of concentrical dikes

that radiate along Sangre de Cristo.

e) Rio Grande Rift, located 10 miles NW of Taos, CO, I-64. This is defined as a

continental rift. This rift is defined by a series of Quaternary basalts. In addition,

seismic studies along this rift reveal a well defined velocity zone at the base of the

crust. Also, high heat flow measurements have indicated a crustal thinning along

this rift system.

f) Cochina Mesa – This formation is defined by the following groups of orogenies:

(1) Cochiti Formation (13.1- 1.6 Ma), which is a pre-caldera, mafi

(intermediate to volcanic) formation.

(2) Caldera – two events produced it:

Tsiringe Member (1.22 Myr) – Defined by a series of felsic ignimbrites

(e.g. Valles caldera).

Otowi Member (1.6 Myr), slope forming (e.g. Toledo Caldera)

Both of these members constitute the Bandalier Tuff

(3) Resurgent Domes (1.22 Myr) – Formed around of the rift section of the

caldera.

(4) SW Moab Volcano (6000 Ka). This is defined by the Battleship rock (ash flow), el

Cajete (pyroclastic ash), and Banco Bonito.

Geology of the Summitville Deposit

Significant remarks regarding the geology of Summitville deposit are provided by

Gray and Coolbaugh (1994). According to these authors, the Summitville deposit lies

within the large, mid Tertiary San Juan Volcanic field. In addition, San Juan volcanism

(35 Ma) produced the series of calderas defined in the previous section. This volcanic

activity let to the formation of several domes among which is the South Mountain quartz.

Geology of the Summitville/Platoro caldera

Moreover, According to Gray and Coolbaugh (1994), the Summitville deposit is located

in the southeastern San Juan volcanic field, approximately 10 km northwest of Platoro,

Colorado. In addition, these authors added that the Summitville deposit is situated near

the intersection of the regional Park Creek-Elwood Creek-Platoro fault system and the

ring fracture zone of the nested Platoro and Summitville calderas (Gray and Coolbaugh,

1994). Remarkable about this area is the series of magmatic hydrothermal, epithermal

deposits that are normally associated with significant gold deposits. In addition,

according to the USGS Survey Bulletin, mining of this gold deposits using cyanide

solutions is what generate the major concern of acid drainage at Summitville mine area.

Results:

See graph provided in Table1 below.

Alamosa River~ 2-3 mi east of Whightman Fork 41 79.08 0.3 1.14 0.2 0.168 5.6 6.34 35 85

Conffluence of Whightman Fork and Alamosa River

a) 22 60.91 0.45 1.2 0.01 1.645 5.25 6.45 20.4

74.14

b) 77 275.73 0.14 0.93 0.02 0.456 4.75 5.85 99.4 44

Conffluence of Bitter Creek and Alamosa River 60 106.73 3.02 6.047 0.01 0.03 4.5 3.96 410 0.27

Alum Creek 100 739.54 3.3 110.7 0.27 0.189 3.75 3.175 471 0.39

Iron Creek on the SW side of Lookout Mountain 31 77.36 0.65 5.56 0.01 0.3042 4.75 4.45 343 2.9

Cattle Guard Crossing, SW flank of Sheepshead Mtn. 19 20.71 ND 0.22 0.05 0.01 5.25 6.725 200 Low

Western Margin of Schinzel Flats 5 27.5 0.36 0.648 0.02 0.02 5 6.4 106 Low

whightman Fork headwaters NW of the Summitville deposit ND 15 0.11 0.347 ND 0.02 5 6.21 75 0.5

Whightman Fork Just below the Summitville mine

a) 300 469 0.69 10.64 0.32 3.063 5 4.68 269 48

b) 50 218 1.59 1.084 0.45 0.347 4 5.32 358 0.4

Mossy Stop 330 1266 30.8 74 7.7 20.6 3.5 3.1 494 ND

Table1. This table illustrates the results we obtained from our analysys of the water chemestry at Summitville and the avarage from 1995-2006

Discussions:

Table1. includes both the result of the water chemistry measurements obtained

this year and the average values of previous measurements (from 1995 to 2006) at the

Summitville mine area. From these results we can see that there has been a significant

progress in reducing the amount of ion, sulfate, and copper going into the drainage

system at the Summitville mine area. For instance, the results obtained from the

measurement of sulfate this year is almost half the average amount of sulfate that was

loaded into the Alamosa River from 1995 to 2006. This reduction on the amount of

sulfuric acid and heavy metals going into the Alamosa River and its affluences has

significantly improved the water quality along this drainage system. This general

improvement of the water quality can be observed in the values of PH that we measured

this year compared to the general average of the PH values measured between1995-2006.

Therefore, we can conclude from these results that the EPA’s environmental protection

plan at Summitville mine are is having a great impact in reducing the acid drainage and

improving the water quality in this area.

Conclusions

Moreover, the catastrophe at Summitville is a reminder of what can go wrong

whenever the urge for profit overshadow the attention that should be paid to the natural

landscape. In addition, though the mining of ore deposits appears to be inevitable in

modern societies, however, considerations must be taken into account to manage these

resources in an efficiently way in order to minimize our environmental footprint and to

avoid catastrophes like the one that took place in Summitville.

References:

Gray, J.E Coolbaugh, MF., Plumlee, G.S., and Atkinson, W.A., 1994, Environmental Geology of the Summitville mine, Colorado: Economic Geology, V.89, p.2006-2014.

Gray, J.E., and Coolbagh, M.F., 1994, Geology and Geochemestry of Summitville, Colorado: An epithermal acid sulfate deposit in a volcanic dome: Economic Geology, V.89, p.0000-0000.

Environmental considerations of active and abandoned mine lands : lessons from Summitville, Colorado / Compiled by Trude V.V. king wotj Contributions from Cathy M. Ager… [et al.] p. cm.-(U.S. Geological Survey bulletin : 2220)