Sulphur isotopic evidence for the genesis of the Au-Ag-Sb-W mineralization of the Fairbanks mining district, Alaska

Introduction -- Sampling and analytical technique -- Results and discussions -- References.Sulphur dioxide from sulphides was extracted for analysis by oxidation with Cuprous oxide at 1070º C, using essentially the method described by Robinson and Kusakabe (1975). The isotopic analyses of the purified sulphur dioxide were made on a modified Micromass 602 mass spectrometer with heated inlet system. The results were corrected for isobaric interference assuming a constant oxygen isotopic content and instrumental crosstalk (Coleman, 1977; 1980) and expressed in conventional del notation with respect to the Canon Diablo meteoritic troilite standard

A Summary of gold fineness values from Alaska placer deposits

This report is the first in a series of publications by the Mineral Industry Research Laboratory and the Alaska Division of Geological and Geophysical Surveys under a special appropriation by the Alaska State Legislature to the School of Mineral Industry to conduct a "Mineral Appraisal of Interior Alaska Mining Districts".Funding for the report was supplimented by a grant under the Mining and Mineral Resources Research Institute, Office of Surface Mining, U.S. Department of Interior

Compilation of the data on the land withdrawals in Alaska

Major decisions an the use and disposition of land in Alaska are being made by the State and Federal governments. These decisions will affect the utilization of all our land resources including minerals. Since minerals are an essential component of our existance, the availability and access to minerals is an important issue. There are approximately 2600 land orders and acts classifying land in Alaska that restrict the utilization of our minerals resources. As of April 1977, approximately twenty-six percent of Alaska, or 100,875,391 acres was open to mineral entry and location under the Federal Mining Laws and the State Mining and Mineral leasing Laws

Landsat linear features and mineral occurrences in Alaska

In order to develop and better understanding of the regional structural controls of the metallic mineral deposits of Alaska, a detailed examination was made of the linear features and trends interpreted from Landsat imagery. In addition, local structural features and alteration zones were examined by ratio analysis of selected Landsat images. The linear trend analysis provided new regional structural data for previously proposed mineral deposit models and also provided new evidence for the extension of the existing models. Preliminary evidence also suggests linear intersection control of some types of mineral occurrences and that trend analysis may result in the definition of areas favorable for future mineral exploration. Ratio image analysis indicates that alteration zones and local structural features can be identified by use of Landsat imagery. Ratio image analysis for the definition of alteration zones must be used with caution, however, since the alteration associated with the various mineral deposits may not be differentiated by the technique.This research was supported by a grant from the Mining and Mineral Resources Research Institute, Office of Surface Mining, U.S. Department of Interior

Metallogeny of the Fairbanks Mining District, Alaska and adjacent areas

The Fairbanks mining district encompasses an area of 1500 km2 (600 miles2) centred just north of the City of Fairbanks, Alaska. The district is one of six mining areas located in or near the northwestern margin of the Yukon-Tanana Uplands of east-central Alaska and the Yukon Territory, Canada. The six mining districts in Alaska (Fairbanks, Circle, Steese, Richardson, Tolovana and Kantishna) and the Klondike district nearby in the Yukon Territory, have an aggregate placer gold production of 25 million troy ounces. This production establishes the region as one of the largest gold producing areas of North America. The aim of the present investigation is to define, classify and explain the genesis of the several primary sources from which the placer gold deposits of the region were derived. Through geological mapping and sampling of the districts, the 350 identified primary mineral occurrences are classified into eight categories as follows: (1) metamorphosed volcanic-exhalative and associated low-sulfide Au-quartz veins, (2) Cu-Mo-Au porphyries, (3) precious metal enriched massive sulfides, (4) epithermal veins in plutonic rocks, (5) Au-bearing tungsten skarns, (6) Sn greisen-gold-quartz veins, (7) Sediment-hosted gold of the Carlin type, and (8) palaeoplacer gold deposits. Geological mapping and sampling has also established that recent faulting and regional uplift are responsible for stream capture, stream drainage reversal, resorting of stream sediments, and modem alluvial placer formation. The volcanic-exhalative mineralization is hosted in metamorphosed low-K tholeiitic basalts, Ca-poor rhyolitic tuffs, and cherts. In the Fairbanks district the rocks are informally referred to as the Cleary sequence. Detrital zircons from the sequence yield U-Pb ages in the ranges 1.2, 1.3- 1.4, 1.8-1.9,2.5, and 3.4 Ga. The bimodal volcanic rocks are enriched in Au, Ag, As, Sb, and W. Average gold contents of the rocks exceed average crustal abundances by two orders of magnitude. Locally the metavolcanic rocks contain base metal massive sulfide mineralization with grades up to 20% combined Pb-Zn, 3 g/tonne Au, and 500 g/tonne Ag. These metavolcanic rock are correlated with those occurring in the Kantishna district (Spruce Creek sequence) and in the Circle district (Bonanza Creek sequence). The mineralized bimodal metavolcanic suite is thus shown to extend along strike for 350 krn (210 miles) through the Yukon-Tanana Terrane. In the Fairbanks district the Cleary sequence rocks are thrust over Type C eclogites. These eclogites trend northeasterly along the regional strike to the Circle quadrangle and are correlated with the eclogites of the central Yukon Territory. Lead 206/204 and 207/204 ratios from galena from the metavolcanic sequences and from the vein deposits are similar with average values of 19.10 and 15.69 respectively. The eclogitic rocks are less radiogenic with 206/204 and 207/204 ratios of 18.80 and 15.65 respectively. Low sulfide Au-quartz veins within the metavolcanic sequences are shown to be the product of multiple thermal and deformational events in the terrane taking place at 160-185, 140-145, and 90-125 Ma, K-Ar. Studies of the fluid inclusions in the metamorphic and vein quartz demonstrate that fluid compositions (1-20 mole % CO2; 3-5 wt % NaCl equiv.) and homogenization temperatures (275-375°C) are closely similar. Gold contents of the vein systems range from 5 to 18 g/tonne. Calc-alkaline plutons of Cretaceous (85-1 10 Ma) and Tertiary (50-70 Ma) age K-Ar host epithermal veins, Sn-greisen, and W-skarn mineralization, all of which are demonstrably gold-bearing. Rb-Sr initial ratios for the mineralized composite plutons are greater than 0.71 1 indicating that anatexis of the lower crust was the source of the granitic magma. The Cu-Mo-Au porphyry mineralization is hosted in the Tertiary plutons that intrude lower Palaeozoic and Mesozoic sediments of the North American Continental Margin (NACM) in the Tolovana district. The NACM rocks are separated from the metavolcanic sequence by the eclogitic rocks and by major thrust faults. Paleoplacer Au deposits hosted in continental clastic rocks of Eocene to Pliocene age are described. These have formed in small grabens adjacent to major strike-slip faults bounding the Yukon-Tanana Terrane on the northeast and southwest respectively. These structures, the Tintina and Denali Faults, controlled sedimentation and placer formation in these grabens. Using compilations of tonnage/grade data from examples of primary deposits analogous to those identified in the Yukon-Tanana Terrane, it is shown that a single large-scale deposit of any of these types could have supplied all the gold contained in the placer deposits of the region.A thesis in two volumes submitted for the degree of Doctor of Philosophy of the University of London. Department of Geology Royal School of Mines, Imperial College of Science, Technology, and Medicine, London

Mineral investigations of D-2 lands in the Philip Smith Mountains and Chandler Lake quadrangles

Eight hundred and sixty-five stream sediment samples were collected over an area of approximately 2,120 square kilometers (828 square miles) in the Chandler Lake and Philip Smith Mountains quadrangles (Fig. 1). The samples were analyzed by atomic absorption methods for Cu, Pb, Zn, Ag and Mo. Statistical reduction of the data resulted in the definition of 86 anomalous samples. The majority of the anomalous samples were from streams draining either the Hunt Fork Shale, Kanayut Conglomerate, or the Lisburne Group. The anomalous samples are grouped in ten separate areas; eight of these areas warrant additional field examination. The number of geochemical anomalies within the area indicates that region has good potential for copper, lead and zinc sulfide mineral deposits.Introduction -- Objective -- Previous investigations -- Regional geology and petrology -- Structural geology -- Geochemistry -- Mining activity and economic geology -- Summary and conclusions -- References cited -- Appendix

Evaluation of the mineral resources of the pipeline corridor, phases i and ii

In accordance with U. S. Bureau of Mines (U.S.B.M.) Grant No. G0166180 entitled, “Evaluation of the Mineral Resources of the Pipeline Corridor”, the Mineral Industry Research Laboratory (M.I.R.L.), of the University of Alaska, completed an examination of the mineral resource potential of the federal utility corridor established for the trans-Alaska pipeline. The contract was completed under the direction of the Principal Investigator, Paul A. Metz and the Associate Investigator, Mark S. Robinson.Introduction -- Section I. Geology and mineral resources of the Valdez quadrangle -- Section II. Geology and mineral resources of the Gulkana quadrangle -- Section III. Geology and mineral resources of the Mt. Hayes quadrangle -- Section IV. Geology and mineral resources of the Big Delta quadrangle -- Section V. Geology and mineral resources of the Fairbanks quadrangle -- Section VI. Geology and mineral resources of the Livengood quadrangle -- Section VII. Geology and mineral resources of the Tanana quadrangle --Section VIII. Geology and mineral resources of the Bettles quadrangle -- Section IX. Geology and mineral resources of the Wiseman quadrangle -- Section X. Geology and mineral resources of the Chandalar quadrangle -- Section XI. Geology and mineral resources of the Philip Smith Mountains quadrangle -- Section XII. Geology and mineral resources of the Sagavanirktok quadrangle

Baseline geochemical studies for resource evaluation of D-2 Lands - geophysical and geochemical investigations at the Red Dog and Drenchwater Creek mineral occurrences

Major zinc, lead and barite mineralization has been discovered at Red Dog and Drenchwater Creeks in the DeLong Mountains of north-western Alaska. The host rocks for the mineral occurrences are carbonates, cherts, shales, and dacitic volcanic rocks of the Mississippian Lisburne Group. The host rocks are deformed in a narrow belt of imbricate thrust sheets that extend from the Canadian border to the Chukchi Sea. The rocks strike generally east-west and dip to the south. The sulfide minerals occur as stratiform mineralization parallel to bedding planes, as breccia fillings and vein replacements, and as disseminations in the various host rocks. The primary ore minerals are sphalerite, pyrite, pyrrhotite, and galena. Barite occurs as massive beds up to 90 meters (300 feet) thick at Red Dog Creek and as nodules, veinlets, and disseminations at Drenchwater Creek. Close spaced soil sampling, mercury vapor sampling, and magnetic and radiometric surveys were conducted over the areas of exposed sulfide mineralization to test the response of these techniques to these types of deposits in northern Alaska. There is potential for additional deposits of this type in the Lisburne Group of the entire northern Brooks Range. These techniques provide a rapid low cost method for the discovery and preliminary evaluation of these types of mineral occurrences in northern Alaska.Introduction -- Objectives -- General geology of the Red Dog Creek and Drenchwater Creek mineral occurrences -- Red Dog Creek mineral occurrence -- Location and previous investigations -- Regional geology and petrology -- Geochronology and structural geology -- Economic geology -- Drenchwater Creek mineral occurrence -- Location and previous investigations -- Regional geology and petrology -- Geochronology and structural geology -- Economic geology -- Geophysical and geochemical data collection, analysis, and reduction - Red Dog Creek -- Geophysical and geochemical data collection, analysis, and reduction - Drenchwater Creek -- Summary and conclusions -- References cited -- Appendices

Evolutionary Dynamics on Small-Order Graphs

Abstract. We study the stochastic birth-death model for structured finite populations popularized by Lieberman et al. [Lieberman, E., Hauert, C., Nowak, M.A., 2005. Evolutionary dynamics on graphs. Nature 433, 312-316]. We consider all possible connected undirected graphs of orders three through eight. For each graph, using the Monte Carlo Markov Chain simulations, we determine the fixation probability of a mutant introduced at every possible vertex. We show that the fixation probability depends on the vertex and on the graph. A randomly placed mutant has the highest chances of fixation in a star graph, closely followed by star-like graphs. The fixation probability was lowest for regular and almost regular graphs. We also find that within a fixed graph, the fixation probability of a mutant has a negative correlation with the degree of the starting vertex. 1