An oxygen-isotope study of water-rock interaction in the granite of Cataract Gulch, western San Juan Mountains, Colorado

Larson, Peter B.; Taylor, Hugh P.

doi:10.1130/0016-7606(1986)97<505:aosowi>2.0.co;2

Cited by 24 publications

(5 citation statements)

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“…2A and 3A). The granite is coarse grained (2-8 mm) and mineralogically uniform where undeformed (Larsen and Cross, 1956;Larson and Taylor, 1986a). The granite is intruded by numerous Ordovician to Cambrian diabase dikes, which mostly have a west to northwest orientation (Lipman, 1976b).…”

Section: Geology Of Lake City Calderamentioning

confidence: 99%

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Controls on hydrothermal fluid flow in caldera-hosted settings: Evidence from Lake City caldera, USA

Garden¹,

Gravley²,

Kennedy³

et al. 2017

Geosphere

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Silicic caldera volcanoes are often associated with hydrothermal systems economically important for electricity generation and localization of ore deposits. Despite their potential importance, the poor exposure that is typical in caldera settings has limited the number of detailed studies of the relationship between caldera structures and fluid flow. We use field mapping, outcrop scale scanline transects, and petrographic analyses to characterize fault rocks, alteration, and veins in the well-exposed 22.9 Ma Lake City caldera fossil hydrothermal system. The caldera margin consists of relatively straight segments linked by more structurally complex intersections; these structural intricacies produce a zone of deformation that can reach >300 m wide. Structural analyses show that the wide (up to ~60 m) fault core of the ring fault contains abundant subparallel veins, with orientations similar to that of the caldera margin. Smaller displacement faults inside the caldera generally have narrow (<1 m), hydrothermally cemented fault cores with more variably oriented veins in the surrounding damage zone. These findings at Lake City illustrate that fluid flow is controlled by lithology and the location and displacement of faults, e.g., ring fault versus intracaldera fault. Fault connectivity is another key control. We propose a conceptual model where fluid flow in caldera-hosted settings is influenced by: (1) the presence of favorable lithologies (proximity to magmatic intrusions and/or the presence of permeable lithologies), (2) a high density of faults and fractures, and (3) favorable orientations of faults and fractures that promote the formation of discontinuity intersections.

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Section: Geology Of Lake City Calderamentioning

confidence: 99%

“…Oxygen-isotope data show that the basement granite is progressively more altered closer to the margin of the LCC (Fig. 2B) ( Larson and Taylor, 1986a). Meteoric water is the principal source of hydrothermal fluid in shallow systems such as Lake City.…”

Section: Geology Of Lake City Calderamentioning

confidence: 99%

Controls on hydrothermal fluid flow in caldera-hosted settings: Evidence from Lake City caldera, USA

Garden¹,

Gravley²,

Kennedy³

et al. 2017

Geosphere

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“…Similar alteration has affected rocks in the Capitol City area (Slack, 1976;Steven and others, 1977). Oxygen-isotope data also indicate hydrothermal alteration in the study areas (Larson, 1983;Larson and Taylor, 1986). Electrical studies suggest that much intensely altered rock is associated with the ring fault in the Burrows Park area (pi.…”

Section: Evaluation Of Mineral Resource Potential For Epithermal Depomentioning

confidence: 90%

“…Regional propylitic alteration is widespread especially in the lower two members of the Sunshine Peak Tuff (Hon, 1987), in the lower part of the Eureka Member of the Sapinero Mesa Tuff (Lipman, 1976a), and in the Proterozoic rocks closest to the ring fault of the Lake City caldera and to the Eureka graben (Larson and Taylor, 1986). Quartz-sericite-pyrite alteration, corresponding to hematite-and limonite-altered areas on plate 1, occurs around the resurgent intrusion in the Lake City caldera and in most rocks adjacent to veins in the two study areas (Hon, 1987).…”

Section: Evaluation Of Mineral Resource Potential For Epithermal Depomentioning

confidence: 99%

Mineral resources of the Redcloud Peak and Handies Peak Wilderness Study Areas, Hinsdale County, Colorado

Sanford¹,

Grauch²,

Hon³

et al. 1987

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Geochemistry 11 Analytical methods 11 Results of analyses of rock samples 12 Results of analyses of stream-sediment samples 12 Geophysics 14 Gravity survey and results 14 Aeromagnetic survey and results 17 Aeroradiometric survey and results 17 Electrical survey and results 20 Mineral and energy resource potential 20 Epithermal precious-metal (silver and gold) and base-metal (principally lead, zinc, and copper) deposits 20 Criteria for recognition of epithermal deposits 20 Evaluation of mineral resource potential for epithermal deposits General statement 22 Vein-type epithermal deposits 23 Breccia-pipe-type epithermal deposits 23 Volcanic-hosted disseminated-type epithermal deposits 23 Clastic-sediment disseminated-type epithermal deposits 26 Porphyry-type molybdenum and (or) copper deposits 26 Mineral resource potential for porphyry-type deposits in the Redcloud Peak Wilderness Study Area 26 Mineral resource potential for porphyry-type deposits in the Handies Peak Wilderness Study Area 29 Alunite (aluminum) deposits 29 Uranium deposits 30 Mineral resource potential for vein uranium deposits 30 Mineral resource potential for disseminated uranium deposits 30 Energy sources other than uranium 30 Recommendations for further study 30 References cited 32 Appendix 37 Contents V 1. Comparison of trace-element concentrations in rock samples, San Juan Mountains 14 2. Distribution of anomalous elements and oxides in stream-sediment samples, Redcloud Peak and Handles Peak Wilderness Study Areas 15

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“…Such enrichment is also known for granitoid rocks affected by exchange with meteoric water and/or brines of seawater origin (e.g., Wenner and Taylor, 1976;Harper et al, 1995;Beyth et al, 1997). Igneous rocks with δ 18 O WR values lower than +6‰ can either form through the assimilation of a low-18 O protolith into the magma chamber (e.g., Bacon et al, 1989;Gilliam and Valley, 1997;Balsley and Gregory, 1998;Bindeman and Valley, 2000;Zheng et al, 2004) or by post-magmatic alteration at higher temperatures (generally >300 °C) (e.g., Taylor, 1971Taylor, , 1974Taylor, , 1977Larson and Taylor, 1986). The δD WR values for the majority of igneous rocks fall in the range of -85 to -50‰ (e.g., Taylor, 1974Taylor, , 1977.…”

Section: Signifi Cance Of the Distribution Of Low δ 18 O Wr Valuesmentioning

confidence: 99%

Regional 18O-depletion of Neoproterozoic igneous rocks from Avalonia, Cape Breton Island and southern New Brunswick, Canada

Potter

Longstaffe

Barr

2008

Geological Society of America Bulletin

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Neoproterozoic igneous rocks of the Avalonian Mira terrane, Cape Breton Island, and Caledonia terrane, southern New Brunswick, have experienced regional 18 O-depletion. The majority of these rocks have δ 18 O WR values between -1 and +6‰, markedly different from igneous rocks of the inboard Ganderian terranes, which have normal-high δ 18 O WR values of +7 to +12‰. The 18 O-depletion of these Avalonian terranes resulted from pervasive hydrothermal alteration. All of the igneous rocks contain classic propylitic alteration assemblages of turbid feldspar, chlorite, epidote, sericite, and calcite and host multiple generations of veins containing the same phases. The δ 18 O values of the rock-forming minerals show strong disequilibrium with Δ qtz-fs ranging from +2.5 to +11.0‰ and Δ kfs-plg from -0.5 to +1.0‰. Such values are indicative of post-magmatic hydrothermal alteration. The hydrothermal alteration occurred at ca. 560-550 Ma during initial transcurrent rifting of Avalonia at the Gondwanan margin. The development of rift-wrench basins with associated bimodal volcanism allowed large volumes of hydrothermal fl uids to penetrate and circulate within Mira and Caledonia terrane crust before its submergence in the early Cambrian (ca. 540-530 Ma). The hydrothermal fl uids were predominantly meteoric, although the presence of a significant seawater component cannot be ruled out. The almost ubiquitous 18 O-depletion exhibited by the Neoproterozoic rocks in these Avalonian terranes is absent in the associated Ganderian terranes, suggesting that Avalonia remained separate from Ganderia until at least the Cambrian-Ordovician. This 18 O-depletion provides an additional geochemical tool for identifi cation of Avalonian crust in other areas of the Appalachians and Europe.

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An oxygen-isotope study of water-rock interaction in the granite of Cataract Gulch, western San Juan Mountains, Colorado

Cited by 24 publications

References 0 publications

Controls on hydrothermal fluid flow in caldera-hosted settings: Evidence from Lake City caldera, USA

Controls on hydrothermal fluid flow in caldera-hosted settings: Evidence from Lake City caldera, USA

Mineral resources of the Redcloud Peak and Handies Peak Wilderness Study Areas, Hinsdale County, Colorado

Regional 18O-depletion of Neoproterozoic igneous rocks from Avalonia, Cape Breton Island and southern New Brunswick, Canada

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