Geochemistry and Stable Isotopes of Surface Water and Groundwater in the Continental Pit in Butte, Montana, USA

The Continental porphyry Cu‐Mo mine, located 2 km east of the famous Berkeley Pit lake of Butte, Montana, contains two small lakes that vary in size depending on mining activity. In contrast to the acidic Berkeley Pit lake, the Continental Pit waters have near-neutral pH and relatively low metal concentrations. The main reason is geological: whereas the Berkeley Pit mined highly‐altered granite rich in pyrite with no neutralizing potential, the Continental Pit is mining weakly‐altered granite with lower pyrite concentrations and up to 1‐2% hydrothermal calcite. The purpose of this study was to gather and interpret information that bears on the chemistry of surface water and groundwater in the active Continental Pit. Pre‐existing chemistry data from sampling of the Continental Pit were compiled from the Montana Bureau of Mines and Geology and Montana Department of Environmental Quality records. In addition, in March of 2013, new water samples were collected from the mine’s main dewatering well, the Sarsfield well, and a nearby acidic seep (Pavilion Seep) and analyzed for trace metals and several stable isotopes, including dD and d18O of water, d13C of dissolved inorganic carbon, and d34S of dissolved sulfate. In December 2013, several soil samples were collected from the shore of the frozen pit lake and surrounding area. The soil samples were analyzed using X‐ray diffraction to determine mineral content. Based on Visual Minteq modeling, water in the Continental Pit lake is near equilibrium with a number of carbonate, sulfate, and molybdate minerals, including calcite, dolomite, rhodochrosite (MnCO3), brochantite (CuSO4·3Cu(OH)2), malachite (Cu2CO3(OH)2), hydrozincite (Zn5(CO3)2(OH)6), gypsum, and powellite (CaMoO4). The fact that these minerals are close to equilibrium suggests that they are present on the weathered mine walls and/or in the sediment of the surface water ponds. X‐Ray Diffraction (XRD) analysis of the pond “beach” sample failed to show any discrete metal‐bearing phases. One of the soil samples collected higher in the mine, near an area of active weathering of chalcocite‐rich ore, contained over 50% chalcanthite (CuSO4·5H2O). This water‐soluble copper salt is easily dissolved in water, and is probably a major source of copper to the pond and underlying groundwater system. However, concentrations of copper in the latter are probably controlled by other, less‐soluble minerals, such as brochantite or malachite. Although the acidity of the Pavilion Seep is high (~ 11 meq/L), the flow is much less than the Sarsfield Well at the current time. Thus, the pH, major and minor element chemistry in the Continental Pit lakes are buffered by calcite and other carbonate minerals. For the Continental Pit waters to become acidic, the influx of acidic seepage (e.g., Pavilion Seep) would need to increase substantially over its present volume.

Geology of the Butte Ore Deposit

Dr. John Dilles discusses the geochemistry of the porphyry Cu-Mo resource found at at Butte, Montana. The porphyry formed from dilute magmatic fluids that contained 1,000s of ppm Cu between 66 and 64 Ma, and at depths of ~8 km. The porphory is zoned from innermost Cu (Ag) ore; to mixed intermediate Cu (Zn, Ag) / Zn-MJn-Ag (Cu, Pb, Au) ore; to an outer Mn-Ag (Pb) ore that grades to barren quartz.

Shallow Groundwater Quality and Geochemistry in the Shields River Basin, South-Central Montana

Water samples were collected from 33 domestic wells, 2 springs, and 3 streams in the Shields River Basin (Basin) in southwest Montana. Samples were collected in 2013 to describe the chemical quality of groundwater in the Basin. Sampling was done to assess potential impacts to water quality from recent exploratory oil and gas drilling and to establish baseline water quality conditions. Wells were selected in areas near and away from oil and gas drilling and in areas susceptible to contamination. Water samples from surface water sites were collected in October to characterize base flow conditions. Physical characteristics of the land surface, soils, and shallow aquifers were used to assess groundwater susceptibility to contamination from the land surface. This analysis was completed using GIS. Samples were analyzed for major ions, trace metals, water isotopes of oxygen and hydrogen. A subset (24) of samples were analyzed for tritium and organic constituents (GRO, DRO, BTEX, methane, ethylene, and ethane). One sample exceeded the human health drinking water standard for selenium. Dissolved methane and ethylene gas were detected in six samples at concentrations less than 0.184 milligrams per liter. Three locations were resampled in 2014, and no methane or ethylene was detected. Shallow groundwater and streams are generally calcium- or sodium-bicarbonate type water with total dissolved solids concentration less than 300 milligrams per liter. Some wells produce either sodium-chloride or sodium-sulfate type water suggesting slower flow paths and more rock-water interaction. Tritium concentrations suggest that older water (TU< 0.8), recharged prior to the mid-1950’s, is generally sodium type, whereas younger water (TU > 4) is generally a calcium type. Water-quality data from this study were compared to available historic data in the Basin. Additionally, the USGS Produced Waters Geochemical database was queried for chemical data of produced waters from reservoir rocks throughout Montana and the surrounding states. Comparisons to historic and produced water chemical data suggest no impact to shallow groundwater quality from exploratory oil and gas drilling.

Geology and Ore Deposits of the Butte-Highland Gold Mine.

The Butte-Highland mine is situated at the head of Basin Creek, in the Highland mining district, Silver Bow County, about 14 miles south of Butte. The tunnel portal and present surface plant are at an elevation of about 7350 feet above sea level, facing westward across the head of Basin Creek valley. The "ghost" mining town of Highland lies a mile to the east, near the forks of Fish Creek. Access to the mine is obtained at present from Beaudine's siding, 12 miles west. The property may also be reached, with difficulty, over poor roads from Limekiln hill, or from Moose Creek.

The General Geology of the Cardwell Mining District

The Cardwell Mining District is part of the greater Whitehall Mining District. The district is situated about four miles to the east and northeast of Whitehall in the southern end of the Bull Mountains which are near the Continental Divide. The first reported production was in 1896 after the dis­covery of the Mayflower Mine. Mining has been carried on in­termittently and on a small scale since that time.

The Geology of Lost Creek Canyon with Special Reference to Igneous Activity

This investigation was undertaken primarily as a problem in geologic mapping, coupled with a study of stratigraphy, glaciation, igneous phenomena, and structure. The area is admirably suited to a study of geology and geologic events. Because it is small in extent, the area was studied in some detail during the time which was devoted to field work. The record of igneous activity of past geological ages is re­markably well exposed, since Lost Creek Canyon was carved through the roof of a stock or batholith by the glaciers of the Pleistocene epoch.

Geology of some Gold Deposits of Montana

Gold is one of the rarer metals in nature, and chemically it is one of the most inactive. Gold forms stable, natural compounds with few other elements, and only with metals.

Geology and Ore Deposits of the Golden Era and Goldfinch Mines, Argenta Mining District, Montana.

This report includes the results of geological investigation of a small area in the northern part of the Argenta mining district. Approximately two square miles were mapped. The underground working of the three mines only were accessible: the Goldfinch. Golden Era, and Mayday mines.

Geology and Ore Deposits of the Golden Messenger MIne, Lewis and Clark County, Helena, Montana.

The Golden Messenger Mine which is approximately twenty-three miles northeast of Helena, Montana, near York, on Trout Creek, has long presented several problems of both theoretical and practical interest.

The Geology of the Southern Central Portion of the Morrison Cave Area.

Morrison Cave is located about 50 miles southeast of Butte, Montana. It was named after the man who discovered it. Later it was taken over by the State and renamed Morrison Cave State Park. Recently the government with the aid of the Civilian Conservation Corps has built a new road to the cave and has made the interior more accessible. The name of the cave is now Lewis and Clark Cavern National Monument.

The Geology and Ore Deposits of Jardine, Montana

The subject to be covered by this paper is based upon field study made during a six week stay at Jardine. The work began on June 19, 1937 and ended on July 31 of the same year.

Secondary Enrichment of Copper at the Madison Gold Skarn Deposit, Silver Star District, Montana

Secondary Enrichment of Copper at the Madison Gold Skarn Deposit, Silver Star District, Montana. This paper focuses on the chemical reactions responsible for secondary enrichment of copper...we argue that most of the secondary Cu enrichment occurred during a late hydrothermal event that replaced the high temperature skarn mineral assemblage with hematitic jasperoid. Evidence favoring this "hypogene" Cu enrichment hypothesis is presented.

Creating Lakes from Open Pit Mines: Processes and Considerations, Emphasis on Northern Environments

Creating Lakes from Open Pit Mines: Processes and Considerations, Emphasis on Northern Environments. This document summarizes the literature of mining pit lakes (through 2007), with a particular focus on issues that are likely to be of special relevance to the creation and management of pit lakes in northern climates. Pit lakes are simply waterbodies formed by filling the open pit left upon the completion of mining operations with water. Like natural lakes, mining pit lakes display a huge diversity in each of these subject areas. However, pit lakes are young and therefore are typically in a non-equilibrium state with respect to their rate of filling, water quality, and biology. Separate sections deal with different aspects of pit lakes, including their morphometry, geology, hydrogeology, geochemistry, and biology. Depending on the type and location of the mine, there may be opportunities to enhance the recreational or ecological benefits of a given pit lake, for example, by re-landscaping and re-vegetating the shoreline, by adding engineered habitat for aquatic life, and maintaining water quality. The creation of a pit lake may be a regulatory requirement to mitigate environmental impacts from mining operations, and/or be included as part of a closure and reclamation plan. Based on published case studies of pit lakes, large-scale bio-engineering projects have had mixed success. A common consensus is that manipulation of pit lake chemistry is difficult, expensive, and takes many years to achieve remediation goals. For this reason, it is prudent to take steps throughout mine operation to reduce the likelihood of future water quality problems upon closure. Also, it makes sense to engineer the lake in such a way that it will achieve its maximal end-use potential, whether it be permanent and safe storage of mine waste, habitat for aquatic life, recreation, or water supply.

Geology of a Portion of the Bull Mountain Range Jefferson County, Montana

Work was first done on a known section, the south Boulder Section, in order to familiarize the student with the formations. Most of the area was mapped by plane table and telescopic alidade, general features being surveyed by automobile traverse and a pacing traverse.

Geology of the Golden Sunlight Mine and Vicinity

The Golden Sunlight Mine is in the northern part of the Cardwell mining district on the eastern slope of a small range that rises by a series of benches to an elevation of 7,200 at a point five miles east of the town of Whitehall in Jefferson County.