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Comstock Tuff

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Journal Article
Journal: Economic Geology
Published: 01 August 1993
Economic Geology (1993) 88 (5): 1176-1197.
... of magmatic zircons and hornblendes, respectively, from different parts of the Mount Read Volcanics yields a concordant age of 502.6 + or - 3.5 Ma (1Sigma ), which constrains the time of volcanogenic massive sulfide mineralization. The Comstock Tuff from the Tyndall Group in the upper part of the volcanic...
Journal Article
Journal: Economic Geology
Published: 01 April 2003
Economic Geology (2003) 98 (2): 367-385.
... in the southern part of the district, and is generally distal to the footwall in the northern part of Comstock lode. Between the Haywood and Grizzly Hill faults, illitic alteration affects the upper part of the silicic ash-flow tuffs in a wide blanket, but it is not found in the directly overlying Alta andesites...
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Journal Article
Journal: Economic Geology
Published: 01 April 2003
Economic Geology (2003) 98 (2): 387-408.
... of higher and lower permeability appears to be a key process necessary for high-grade ore formation and, most commonly, it is such concentrations of metals that make an epithermal vein district world class. In the world-class silver- and gold-producing Comstock mining district, Nevada, several lines...
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Journal Article
Journal: Economic Geology
Published: 01 January 2000
Economic Geology (2000) 95 (1): 131-142.
...) from surface outcrops of andesite, tuff, and granodiorite in the Comstock lode mining district. The 75-km 2 circular zone of rocks having low δ 18 O values of– 4 to +6 per mil represents an ancient volcanic center where rocks interacted with low 18 O fluids and became propylitized. This field...
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Journal Article
Journal: GSA Bulletin
Published: 01 December 2002
GSA Bulletin (2002) 114 (12): 1535-1549.
...Rónadh Cox; Mark W. Martin; Jana C. Comstock; Laura S. Dickerson; Ingrid L. Ekstrom; James H. Sammons Abstract Quartzite, conglomerate, and shale of the Mazatzal Group record the filling of a Prot erozoic intra-arc basin in central Arizona. U-Pb ages of zircons from rhyolite ash-flow tuff indicate...
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Journal Article
Published: 01 July 2001
Journal of Paleontology (2001) 75 (4): 890-894.
... Hills in the west to the West Cronese Basin in the east and crops out in the Mud Hills, the Yermo Hills, the Alvord Mountains, and the Calico Mountains. Figure 1 —Stratigraphic table for the Barstow Formation with land mammal ages and dated tuffs used to determine the age of the formation...
FIGURES
Journal Article
Journal: GSA Bulletin
Published: 01 July 2004
GSA Bulletin (2004) 116 (7-8): 817-839.
..., and paleomagnetic stratigraphy of these tuffs and rocks now allow dating of local fossil floras. The Comstock, Goshen, Rujada, and Willamette floras have been widely used as evidence for Eocene-Oligocene climatic cooling and drying. Eocene leaves from Comstock and Hobart Butte included such thermophilic taxa...
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Journal Article
Journal: Economic Geology
Published: 01 December 2001
Economic Geology (2001) 96 (8): 1827-1853.
... and include the Comstock Lode, Tonopah, Goldfield, Aurora, Bodie, Paradise Peak, and Rawhide deposits. Low-sulfidation Au-Ag deposits in the bimodal assemblage formed under relatively low oxygen and sulfur fugacities and have generally low total base metal (Cu + Pb + Zn) contents, low Ag/Au ratios...
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Journal Article
Journal: Economic Geology
Published: 01 April 2003
Economic Geology (2003) 98 (2): 425-463.
... narrow and discontinuous gold-bearing siliceous veins. These differences primarily are due to the mafic composition of the host rocks. Mule Canyon differs from low-sulfidation deposits associated with subduction-related calc-alkaline porphyry intrusions, such as the Comstock lode, in that a much smaller...
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Journal Article
Journal: AAPG Bulletin
Published: 01 December 1956
AAPG Bulletin (1956) 40 (12): 2801-2825.
...Franklyn B. Van Houten ABSTRACT Throughout Nevada the most reliable stratigraphic datum in sequences of non-marine Cenozoic sedimentary rocks is a distinctive suite of tuffaceous upper Miocene to middle Pliocene deposits. For convenience of discussion these rocks are referred to as the vitric tuff...
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Journal Article
Published: 15 April 2014
Geological Magazine (2015) 152 (1): 28-40.
...). Indeed, Perkins & Walshe's ( 1993 ) report includes samples with quite different dates and with uncertain or questionable biostratigraphic context. Thus, they report a mean date of 494.4±3.5 Ma on the Comstock Tuff (sample 92–101) above Jago et al .'s ( 1972 ; also...
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Journal Article
Published: 01 February 2000
Mineralogical Magazine (2000) 64 (1): 43-57.
... SHRIMP result for the Mt. Read Volcanics. The SHRIMP data were published before the variability within the SL13 was recognized and before the use of mixture modelling; the full Mt. Read Volcanics ages will be reviewed in detail elsewhere. The revised age of the Comstock tuff from the upper part of the Mt...
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Journal Article
Journal: PALAIOS
Published: 20 September 2019
PALAIOS (2019) 34 (9): 424-436.
... and the cooler middle Eocene. Plant macrofossils were collected from one fluvial site at East Birch Creek approximately 2 m below a 51.9 ± 0.9 Ma tuff. Collections were also made at two co-occurring fluvial sites at Arbuckle Mountain, whose ages are constrained to ca. 44.5–43.8 Ma based on a dated tuff from...
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Journal Article
Journal: Economic Geology
Published: 01 December 2004
Economic Geology (2004) 99 (8): 1665-1686.
... a change from mafic-dominated bimodal volcanism and basin formation to felsic volcanism, folding, and faulting at about 15.6 Ma. From 15.6 to 15.2 Ma, sediments and tuffs were deposited on a relatively impermeable rhyolite flow. During this period, faulting and tilting of the volcanic edifice created...
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Series: Special Publications of the Society of Economic Geologists
Published: 01 January 2001
DOI: 10.5382/SP.08.02
EISBN: 9781629490328
... of the major silver and gold producers in the world. The high-grade silver-gold deposits are of the low sulfidation, adularia-sericite epithermal type, formed during the final stages of igneous and hydrothermal activity of small Eocene quartz monzonitic and andesitic intrusions. The veins are hosted by tuffs...
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Journal Article
Published: 01 January 2001
Journal of Sedimentary Research (2001) 71 (1): 190-204.
... silica (opal-A), that are informally termed "geyser eggs", surround the vent of Waikorohihi, whereas smaller (< 3 cm) geyser eggs are present in the proximal outflow channel of Mahanga. The geyser eggs have nuclei of detrital sinter or rhyolitic tuff. Their cortices are formed of thin concentric...
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Journal Article
Journal: GSA Bulletin
Published: 01 September 2013
GSA Bulletin (2013) 125 (9-10): 1423-1441.
... Hondo Group, a metamorphosed tuff layer from the Pilar Formation yields an age of 1488 ± 6 Ma and represents the first direct depositional age constraint on any part of the Proterozoic metasedimentary succession in northern New Mexico. Detrital zircon from the overlying Piedra Lumbre Formation yield...
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Journal Article
Journal: GSA Bulletin
Published: 01 March 2008
GSA Bulletin (2008) 120 (3-4): 274-299.
... the paleocanyons. Vent-proximal facies consist of lava domes that collapsed to generate block and ash flow tuffs, which in turn were remobilized down-canyon to produce coarse-grained volcanic mudflow and dilute flow (fluvial) deposits. Lava flows are rare; instead, magmas invaded wet volcaniclastic sediment...
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Series: Geological Society, London, Engineering Geology Special Publications
Published: 01 January 2005
DOI: 10.5382/SP.11.06
EISBN: 9781629490359
... volcanic suite, known as the Paleocene belt. It comprises basaltic to rhyolitic lavas and tuffs, subvolcanic porphyritic intrusions, and granitoid stocks that extend from southern Peru to central Chile and range in age from 72 to 40 Ma ( Boric et al., 1990 ; Marinovic et al., 1995 ; SERNAGEOMIN, 2003...
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Image
F ig . 1. Contour map of whole-rock δ 18 O
values (dots) from surface outcr...
Published: 01 January 2000
F ig . 1. Contour map of whole-rock δ 18 O values (dots) from surface outcrops of andesite, tuff, and granodiorite in the Comstock lode mining district. The 75-km 2 circular zone of rocks having low δ 18 O values of– 4 to +6 per mil represents an ancient volcanic center where rocks interacted