A Bentonite Deposit near Warm Springs, Montana

This report deals with a bentonite deposit recently developed, approximately seven miles northeast of Warm Springs, Montana. A group of claims have been staked on the deposit and are owned by the Lincoln Mining Company of Anaconda, Montana. The company also has several claims prospected for silver one mile from its present site of operations, but the silver prospects have failed to produce. The bentonite deposit was discovered incidentally during the course of other development work, and at present two adits have been driven into the side of a mountain, each crosscutting a vein-like mass of bentonite varying from two to three feet in width.

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.

The Jefferson Canyon Gypsum Deposit.

Gypsum deposits are widespread geographically and are in many geo­logic formations. Ordinarily their character and origin, for the most part sedimentary, are not difficult to ascertain. Near Lewis and Clark Caverns, east of Whitehall, Montana, occurs a deposit of gypsum unique in many re­spects.

South Moccasin Kaolin Deposit

Kaolin has never been considered an important economic mineral in Montana. Deposits of Kaolin in this state are not described in the literature and apparently very few deposits have been found.

Geology of a Kyanite Deposit Near Ennis, Montana

A deposit of kyanite, an aluminum silicate mineral used in the ceramic industry, occurs in the low foothills of the Gravelly range about 10 miles south of Ennis, Montana. This study deals primarily with the character and origin of the deposit, and its relationship to the surrounding rocks.

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.

The Christensen Sillimanite Deposit Southeast of Dillon, Montana

The minerals sillimanite, kyanite, andalusite, dumortierite, and topaz comprise a group of minerals whose high alumina content and physical properties are particularly desirable in the manufacture of refractory products. Sillimanite is the least plentiful of the minerals of this group, and for this reason it is not used extensively at the present time. However, it would be very desirable to the refractory industry if a suitable domestic source of supply could be established.

Possible earthquake trigger for 6th century mass wasting deposit at Lake Ohrid (Macedonia/Albania)

Abstract. Lake Ohrid shared by the Republics of Albania and Macedonia is formed by a tectonically active graben within the south Balkans and suggested to be the oldest lake in Europe. Several studies have shown that the lake provides a valuable record of climatic and environmental changes and a distal tephrostratigraphic record of volcanic eruptions from Italy. Fault structures identified in seismic data demonstrate that sediments have also the potential to record tectonic activity in the region. Here, we provide an example of linking seismic and sedimentological information with tectonic activity and historical documents. Historical documents indicate that a major earthquake destroyed the city of Lychnidus (today: city of Ohrid) in the early 6th century AD. Multichannel seismic profiles, parametric sediment echosounder profiles, and a 10.08m long sediment record from the western part of the lake indicate a 2m thick mass wasting deposit, which is tentatively correlated with this earthquake. The mass wasting deposit is chronologically well constrained, as it directly overlays the AD472/AD 512 tephra. Moreover, radiocarbon dates and cross correlation with other sediment sequences with similar geochemical characteristics of the Holocene indicate that the mass wasting event took place prior to the onset of the Medieval Warm Period, and is attributed it to one of the known earthquakes in the region in the early 6th century AD.

Small-Scale Features of Marine Sediments and Their Importance to the Study of Deposit-Feeding

Techniques currently in use by sedimentologists for the study of marine sedment microfabric are of limited use for understandmg the relationship between sediment organic matter and mineral grains. In this article it is shown that by combining standard histological protocols for fixation and dehydration with petrological protocols for resin embedding and thin sectioning, very fine details of the sediment structure can be seen. Because of the ubiquitous presence of the organic matrix, organicmineral aggregates are not seen in situ. Other features of the sediment of importance to deposit-feeders, such as the presence of intact chloroplasts, can be observed through the use of epifluorescence illumination, while partially crossed polarizers help to delimit the grain boundaries. It is suggested that if these procedures can be combined with histological staining techniques, it may be possible to determine the potential food value of sedment on a scale equivalent to that perceived by infaunal deposit-feeders.

Sedimentary Metal Bioavailability Determined By the Digestive Constraints of Marine Deposit Feeders: Gut Retention Time and Dissolved Amino Acids

Contaminant metals bound to sediments are subject to considerable solubilization during passage of the sediments through the digestive systems of deposit feeders. We examined the kinetics of this process, using digestive fluids extracted from deposit feeders Arenicola marina and Parastichopus californicus and then incubated with contaminated sediments. Kinetics are complex, with solubilization followed occasionally by readsorption onto the sediment. In general, solubilization kinetics are biphasic, with an initial rapid step followed by a slower reaction. For many sediment-organism combinations, the reaction will not reach a steady state or equilibrium within the gut retention time (GRT) of the organisms, suggesting that metal bioavailability in sediments is a time-dependent parameter. Experiments with commercial protein solutions mimic the kinetic patterns observed with digestive fluids, which corroborates our previous study that complexation by dissolved amino acids (AA) in digestive fluids leads to metal solubilization (Chen & Mayer 1998b; Environ Sci Technol 32:770-778). The relative importance of the fast and slow reactions appears to depend on the ratio of ligands in gut fluids to the amount of bound metal in sediments. High ligand to solid metal ratios result in more metals released in fast reactions and thus higher lability of sedimentary metals. Multiple extractions of a sediment with digestive fluid of A. marina confirm the potential importance of incomplete reactions within a single deposit-feeding event, and make clear that bioavailability to a single animal is Likely different from that to a community of organisms. The complex kinetic patterns lead to the counterintuitive prediction that toxification of digestive enzymes by solubilized metals will occur more readily in species that dissolve less metals.