Chemical and physical characteristics of alluvium from drill core near the Rabbit Creek gold deposit, Getchell mining district, Humboldt County, Nevada

1989 ◽  
Author(s):  
D.E. Detra ◽  
D.J. Madden-McGuire ◽  
S.M. Smith ◽  
M.L. Silberman ◽  
Theodore Botinelly ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Physical Characteristics ◽  
Mining District ◽  
Drill Core ◽  
Humboldt County

Low-temperature thermal history of the Gilmore Dome area, Fairbanks Mining District, Alaska

1993 ◽  
Vol 30 (4) ◽  
pp. 764-768 ◽  
Author(s):  
John M. Murphy ◽  
Arne Bakke
Keyword(s):  
Gold Deposit ◽  
Fission Track ◽  
Hydrothermal Fluids ◽  
Mining District ◽  
Cooling Path ◽  
Alteration Assemblage ◽  
Zircon Fission Track ◽  
History Of ◽  
Maximum Temperatures ◽  
Fission Track Ages

Eight apatite and two zircon fission-track ages provide evidence of complex Tertiary thermal overprinting by hydrothermal fluids in the Gilmore Dome area. Five ages on apatite from the Fort Knox gold deposit average 41 Ma, one from the Stepovich prospect is 80 Ma, and two from Pedro Dome average 67 Ma. Elevations of these samples overlap but their ages do not, indicating that each area experienced a different thermal history.Ages of apatite from the Fort Knox gold deposit decrease with elevation from 42 to 36 Ma but have data trends indicative of complex cooling. Two ~51 Ma ages on zircon indicate that maximum temperatures approached or exceeded ~180 °C. An alteration assemblage of chalcedony + zeolite + calcite + clay in the deposit resulted from deposition by a paleo-hydrothermal system. The data suggest that the system followed a complex cooling path from > 180 to < 110 °C between 51 and 36 Ma, and that final cooling to below 60 °C occurred after ~25 Ma.The 80 Ma age from Stepovich prospect either resulted from cooling after intrusion of the underlying pluton (~90 Ma) or records postintrusion thermal overprinting sometime after ~50 Ma. The 67 Ma samples from Pedro Dome may also have experienced partial age reduction during later heating. The differences in the data from the different areas and the presence of a late alteration assemblage at Fort Knox suggest that the fluids responsible for heating were largely confined to the highly fractured and porous Fort Knox pluton.

scholarly journals Quantitative Mineral Mapping of Drill Core Surfaces I: A Method for µXRF Mineral Calculation and Mapping of Hydrothermally Altered, Fine-Grained Sedimentary Rocks from a Carlin-Type Gold Deposit

2020 ◽  
Author(s):  
Rocky D. Barker ◽  
Shaun L.L. Barker ◽  
Siobhan A. Wilson ◽  
Elizabeth D. Stock
Keyword(s):  
Gold Deposit ◽  
Sedimentary Rocks ◽  
Potassium Feldspar ◽  
Ore Deposits ◽  
Drill Core ◽  
Raster Data ◽  
X Ray ◽  
Fine Grained ◽  
Core Samples ◽  
Wavelength Dispersive Spectrometry

Abstract Mineral distributions can be determined in drill core samples from a Carlin-type gold deposit, using micro-X-ray fluorescence (µXRF) raster data. Micro-XRF data were collected using a Bruker Tornado µXRF scanner on split drill core samples (~25 × 8 cm) with data collected at a spatial resolution of ~100 µm. Bruker AMICS software was used to identify mineral species from µXRF raster data, which revealed that many individual sample spots were mineral mixtures due to the fine-grained nature of the samples. In order to estimate the mineral abundances in each pixel, we used a linear programming (LP) approach on quantified µXRF data. Quantification of µXRF spectra was completed using a fundamental parameters (FP) standardless approach. Results of the FP method compared to standardized wavelength dispersive spectrometry (WDS)-XRF of the same samples showed that the FP method for quantification of µXRF spectra was precise (R2 values of 0.98–0.97) although the FP method gave a slight overestimate of Fe and K and an underestimate of Mg abundance. Accuracy of the quantified µXRF chemistry results was further improved by using the WDS-XRF data as a calibration correction before calculating mineralogy using LP. The LP mineral abundance predictions were compared to Rietveld refinement results using X-ray diffraction (XRD) patterns collected from powders of the same drill core samples. The root mean square error (RMSE) for LP-predicted mineralogy compared to quantitative XRD results ranges from 0.91 to 7.15% for quartz, potassium feldspar, pyrite, kaolinite, calcite, dolomite, and illite. The approaches outlined here demonstrates that µXRF maps can be used to determine mineralogy, mineral abundances, and mineralogical textures not visible with the naked eye from fine-grained sedimentary rocks associated with Carlin-type Au deposits. This approach is transferrable to any ore deposit, but particularly useful in sedimentary-hosted ore deposits where ore and gangue minerals are often fine grained and difficult to distinguish in hand specimen.

Age and sources of gold mineralization in the Marmato mining district, NW Colombia: A Miocene–Pliocene epizonal gold deposit

2008 ◽  
Vol 33 (3-4) ◽  
pp. 505-518 ◽  
Author(s):  
Colombo Celso Gaeta Tassinari ◽  
Fabio Diaz Pinzon ◽  
Juaquin Buena Ventura
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Mining District

Gold Distribution in Pyrite of the Senjedeh Gold Deposit, Muteh Mining District, NW of Iran

2014 ◽  
Vol 88 (s2) ◽  
pp. 829-830 ◽  
Author(s):  
Zahra Nourian Ramsheh ◽  
Jingwen MAO ◽  
Mohammad Yazdi ◽  
Junfeng XIANG ◽  
Iraj Rasa ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Mining District

ORE CLASSIFICATION OF PSEUDOBRECCIA ORE IN THE 144 ZONE GOLD DEPOSIT: A CHEMICAL REPLACEMENT MODEL, BARE MOUNTAIN RANGE, NEVADA

2020 ◽  
Vol 115 (5) ◽  
pp. 1137-1150
Author(s):  
Bill T. Fischer ◽  
Jean S. Cline
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Selective Dissolution ◽  
Mining District ◽  
Mountain Range ◽  
Late Cambrian ◽  
Southern Nevada ◽  
Replacement Model ◽  
The Matrix ◽  
Host Rocks

Abstract The 144 zone is a pseudobreccia-hosted, disseminated gold deposit that formed in the middle to late Cambrian Bonanza King dolostone along an unconformity with the underlying early to middle Cambrian Carrara limestone at Bare Mountain, southern Nevada. Underground mapping revealed spatial relationships between breccia types, host rocks, and alteration assemblages that are related to gold mineralization. Samples were collected along transects from low- to high-grade Au and were analyzed using petrography, applied reflectance spectroscopy, scanning electron microscopy, and electron probe microanalysis to characterize mineral assemblages and evaluate gold deportment. Two breccia types are identified. Breccia type 1 clasts consist of dolomite, dolomite with phengite, and quartz cemented in a quartz-rich matrix. Breccia type 2 has similar clasts of dolomite, dolomite with phengite, and quartz, but the matrix is phengite dominant. Neither breccia type has a preferred association with gold, which occurs with goethite that replaced pyrite in both breccias. Clast and matrix compositions and textures show that the two breccia types formed at the same time by selective dissolution and replacement of the lowermost Bonanza King dolomite. Fluid-rock reaction transformed massive dolomite into pseudobreccia. Quartz replacement of dolomite plus the precipitation of pyrite, Au, and phengite yielded the 144 zone pseudobreccia matrix. The geology that characterizes gold mineralization in the 144 zone can be applied to exploration throughout Bare Mountain. Other localities where the same stratigraphic contact is cut by silicic dikes of similar age provide drill targets in the mining district.

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