Download or read book Data for Plutonic Rocks and Associated Gold Deposits in Interior Alaska written by Rainer J. Newberry and published by . This book was released on 1995 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quartz Normative Plutonic Rocks of Interior Alaska and Their Favorability for Association with Gold written by L. E. Burns and published by . This book was released on 1991 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mid Cretaceous Plutonic related Gold Deposits of Interior Alaska written by Daniel Thomas McCoy and published by . This book was released on 2000 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Mid-cretaceous gold deposits in interior Alaska are hosted in or near apices of low magnetite plutons that are formed in a broad continental arc. Ore is hosted in 1) anastomosing quartz veins with potassic or albitic envelopes, 2) planar veins and shear zones with sericitic alteration, and 3) pyroxene-rich skarn deposits. This study was undertaken to constrain the fluid and metal source and composition, formation conditions, gold associative mineralogy, age relationships, and areal extent of this mineralizing event. Techniques included reflected light petrographic, 40Ar/39Ar step-heating, stable isotope, fire assay, Mossbauer spectroscopy, electron microprobe, and scanning ion mass spectroscopy analysis. Results suggest ages between 85 Ma and 107 Ma with a 0 to 2 million-year differential between magmatic biotite and hydrothermal veins in the same deposits. Deposits are 10 t0 20 million years younger than local metamorphism. Fluid calculated stable isotopic ratios (ð13C = -9 to -10 per mil; ð18O = 5-10 per mil; ðD = -47 to -100; ð34S = -5 to +5 per mil) suggest gold precipitated from magmatic fluids. Fluid inclusions in ore-bearing quartz contain high CO2 with trapping temperatures and pressures of 270 ̊to 570C̊ and 0.5 to 2 kb respectively. The Fort Knox and Pogo deposits have a strong Au-Bi association and high relative amounts of potassic and albitic alteration with mineralogical evidence for the original existence of maldonite (Au2Bi) or Au-Bi melt subsequently overprinted by native gold + bismuthinite. The True North deposit has a strong Au-As association and no Au-Bi association. It lacks potassic or albitic alteration and contains only sub-micron gold; approximately half chemically bound to arsenopyrite or arsenian pyrite. The Dolphin and Ryan Lode deposits are intermediate in Au-Bi association, gold-associative mineralogy and alteration features. Arsenopyrite geothermometry yield temperatures between 300 ̊and 630C̊ for albitic and potassic alteration and between 250 ̊and 420C̊ for sericitic alteration. 40Ar/39Ar dating and metal ratios suggest that gold mineralization is 1) solely mid-Cretaceous in the Fairbanks mining district, 2) mid-Cretaceous and late Cretaceous in the Kantishna mining district, and 3) mid-Cretaceous and early Tertiary in the Livengood mining district"--Leaves iii-iv.
Download or read book Mineral Deposits of Alaska written by R. J. Goldfarb and published by . This book was released on 1997 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geologic Studies in Alaska by the U S Geological Survey 1996 written by John E. Gray and published by . This book was released on 1998 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geologic Studies in Alaska by the U S Geological Survey 1996 written by and published by . This book was released on 1998 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Geological Survey Circular written by and published by . This book was released on 1984 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Digital Files of Geochemical Analyses of Plutonic Rocks in East central Interior Alaska Compiled from Published Sources written by L. E. Burns and published by . This book was released on 1993 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 1996 Annual Report on Alaska s Mineral Resources written by and published by . This book was released on 1997 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fifth Hutton Symposium written by Shuns? Ishihara and published by Geological Society of America. This book was released on 2005-01-01 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Geological Survey Professional Paper written by and published by . This book was released on 1984 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geology and Ore Deposits 2000 written by Geological Society of Nevada. Symposium and published by . This book was released on 2000 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Exploring Competing Gold System Models in the Valdez Creek Region Clearwater Mountains Alaska written by Jane Marguerite Suhey and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gold deposits located within the accretionary and subduction-related tectonic environment of south-central Alaska are interpreted to have formed via devolatilization of hydrous assemblages through regional metamorphism (orogenic model) or by intrusion-related hydrothermal processes (intrusion-related gold system model). The Valdez Creek mining district is located in the southern Clearwater Mountains of south-central Alaska along the intermontane-insular belt suture of the North American Cordillera. The 67-56 Ma south-vergent Valdez Creek shear zone resulted in the thrusting of North American-derived Maclaren schist (intermontane) structurally above lower greenschist-facies rocks of the Clearwater metasediments (Insular). The ~ 5km thick ductile shear zone preserves a complete inverted Barrovian metamorphic gradient ranging from lower greenschist-facies conditions in the south to upper-amphibolite-facies in the north. This event records the terminal suturing of the Wrangellia composite terrane with the North American margin. Placer gold mining and lode gold exploration is currently focused within the footwall of the Valdez Creek shear zone. The region also contains previously undated Cretaceous intrusive rocks associated with gold-in-soil geochemical anomalies. Here, competing gold system models were investigated to identify the predominant mineralization process. This information is used to improve exploration strategies in the area and further develop our understanding of gold formation in the Clearwater Mountains, Alaska. Constraining mechanisms of gold mineralization through integrating structural analysis, geochemistry, and a multiphase geochronologic framework provides a robust tool to determine dominant ore-forming mechanisms. 40Ar/39Ar and 206Pb/238U geochronological methods were used to determine the timing of gold mineralization and constrain ages of igneous rocks associated with known lode sources. Detrital gold geochemistry methods were used to compare placer gold and lode gold compositions. Bulk rock major and trace element geochemical methods were also used to evaluate a primary gold-model by investigating compositional differences of gold-like elements across the Valdez Creek shear zone. Detailed mapping and structural analysis were completed to test if gold mineralization is compatible with shear zone activity (supporting an orogenic model) or if mineralization was unrelated to regional metamorphism and overprinted by the shear zone from 67-56 Ma (supporting an intrusion-related gold system model). The 206Pb/238U zircon data collected from the alkali pluton suite and the placer system indicates gold-hosting veins were localized within and adjacent to alkaline plutons in the region. These data also indicate that detritus in the placer system was locally derived. White mica 40Ar/39Ar geochronology integration ages from undeformed gold-bearing quartz veins proximal to intrusions supports a young mineralization age for gold between 62.11 Ma to 66.58 Ma. Similarities in gold chemistry were also identified within placer gold samples collected from current mining operations and a lode gold location within the catchment. Structural observations show gold-bearing mineralization in quartz veins is likely synchronous with the penetrative deformation associated with the Valdez Creek shear zone. Discrete and network vein orientations throughout the shear zone have geometries compatible with top-to-the-south shear sense of the Valdez Creek shear zone. These results are compatible with a local gold lode source for the Valdez Creek placer deposit that formed coeval with the Valdez Creek shear zone. Bulk rock major and trace element geochemistry results from across the Valdez Creek shear zone metamorphic gradient show a systematic decrease in As, Cu, Ni, Zn, Pb, and Au across the greenschist-amphibolite facies transition indicating that auriferous fluids may have been derived from the shear zone. We hypothesize that metamorphic fluids generated from the dehydroxylation of chlorite occurred simultaneously with shearing along the Valdez Creek shear zone. In this system, auriferous fluids were likely concentrated within or proximal to rigid intrusion(s) in the footwall of the shear zone, coinciding with vein development and fluid channelization, similar in process to the Juneau Gold Belt.
Download or read book Some Plutonic Rocks of Southwestern Alaska written by Frederic H. Wilson and published by . This book was released on 1977 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Sapporo International Conference on Mineral Resources of the NW Pacific Rim 1994 written by Shunsō Ishihara and published by . This book was released on 1995 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Tintina Gold Belt written by and published by . This book was released on 2000 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metallogenesis and Tectonics of the Russian Far East Alaska and the Canadian Cordillera written by and published by . This book was released on 2005 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt:
