Geochemistry of footwall alteration associated with the early Proterozoic United Verde massive sulfide deposit, Arizona

Vance, R. Kelly; Condie, Kent C.

doi:10.2113/gsecongeo.82.3.571

Cited by 23 publications

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“…The chemical composition of a hydrothermally-formed mineral depends on fluid composition, kinetic effects and the prevailing temperature and pressure (Rose and Burt 1979;Vance and Condie 1987). The fluid composition is a result of the evolution of the fluid.…”

Section: Hydrothermal Alterationmentioning

confidence: 99%

“…If fresh seawater is entrained, Mg-rich minerals may form (with sulphides). The most common alteration asemblages described in the literature are composed of greenschist facies minerals like chlorite + / -sericite ( + / -biotite) (Riverin and Hodgson 1980;Hall 1982;Morton and Nebel 1984;Osterberg et al 1987;Vance and Condie 1987).…”

Section: Hydrothermal Alterationmentioning

confidence: 99%

“…Regardless of the age or the primary composition of the volcano-sedimentary host rocks, the original alteration products mainly comprise chlorite and/or sericite (e.g. Riverin and Hodgson 1980;Hall 1982;Morton and Nebel 1984;Osterberg et al 1987;Vance and Condie 1987). The alteration zone chlorites have characteristic chemical variation trends related to the intensity of alteration and to the position within the zone.…”

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confidence: 99%

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The mineral chemistry of hydrothermally altered and metamorphosed wall-rocks at the Stollberg Fe-Pb-Zn-Mn(-Ag) deposit, Bergslagen, Sweden

Ripa

1994

Mineral. Deposita

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The c. 1.9 Ga old Stollberg sulphide and Mnrich skarn iron ores and sulphide ores in Bergslagen, south-central Sweden are hosted by hydrothermally altered and metamorphosed felsic volcanic and volcaniclastic rocks. The ores are underlain by comformable alteration zones characterized by albite-gedrite-quartz and biotite-muscovite-plagioclase-K-feldspar-quartz + / -garnet assemblages. The present mineralogies are interpreted as medium-grade metamorphic equivalents to the original alteration mineral assemblages. PT-conditions during prograde regional metamorphism are semiquantatively determined to be 510 to 560 ~ at approximately 3 kbar. With increasing modal content of gedrite and biotite in the alteration zones, the Mg/Fe ratios and XMg' S in octahedral positions of these minerals also increase. In the gedrite-bearing strata, whole-rock Mg/Fe ratios remain constant, whereas in the biotite-rich unit the wholerock Mg/Fe trend is parallel to that of the biotites.The trends in the metamorphic mineral composition are interpreted to be a product of original changes in fluid composition during the evolution of a sub-seafloor hydrothermal system. During the initial stage of alteration, Fe-Mn-rich fluids altered the rocks, and during a later stage, the fluids became more Mg-rich, possibly due to entrainment of fresh seawater, and the alteration zones became relatively more Mg-rich. Sulphide precipitation was contemperaneous with Mg metasomatism, suggesting base metal precipitation was a function of the mixing of cool seawater with hydrothermal fluid. It is proposed that early hydrothermal alteration was associated with the deposition of areally extensive Fe-oxide formation, and that Mg metasomatism defines a second stage of hydrothermal activity during which sulphide mineralization overprinted the earlier formed Fe-oxide deposit.

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Section: Hydrothermal Alterationmentioning

confidence: 99%

Section: Hydrothermal Alterationmentioning

confidence: 99%

mentioning

confidence: 99%

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The mineral chemistry of hydrothermally altered and metamorphosed wall-rocks at the Stollberg Fe-Pb-Zn-Mn(-Ag) deposit, Bergslagen, Sweden

Ripa

1994

Mineral. Deposita

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“…Lanphere (1968) obtained Rb-Sr whole-rock ages for metamorphism of 1,640 to 1,660 Ma. Vance and Condie (1987) reported an assemblage of sericite + chlorite + oligoclase for the felsic rocks of the study area and Anderson and Creasey (1958). Formations within the study area, the upper Shea Basalt, the Deception Rhyolite, and the Grapevine Gulch Formation, are characterized by the mineral assemblage sericite + chlorite + quartz + albite, indicative of lower greenschist facies metamorphism (Turner and Verhoogen, 1960;Winkler, 1979).…”

mentioning

confidence: 99%

Stratigraphy and alteration of the host rocks, United Verde massive sulfide deposit, Jerome, Arizona

Gustin

1990

Economic Geology

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The early Proterozoic volcanogenic United Verde massive sulfide orebody is situated within the Cleopatra Member of the Deception Rhyolite. The Cleopatra Member, a porphyritic rhyodacite, has been subdivided into an upper unit and a lower unit. The United Verde orebody, previously interpreted to lie at the top of the Cleopatra Member, is now recognized as lying within the basal section of the upper unit of the Cleopatra Member.The upper unit and lower unit are differentiated on the basis of alteration mineralogy, mineral and rock geochemistry, and lithologic peculiarities. The contact between the two units is marked by sediments at the base of the upper unit, including a distinct green calcitebearing feldspar tuff, chert and hematitic chert layers, and a quartz porphyry conglomerate.The Cleopatra Member contains six distinct alteration types. Five alteration types characterize the lower unit and include two types of moderate chloritic and sericitic alteration (designated B1 and B2), two spatially distinct types of sericitic and silicic alteration (designated S1 and S2), and an area of intense chloritic alteration (designated C). These five alteration types record the effects of hydrothermal alteration by the massive sulfide ore-forming system and of a regional greenschist facies metamorphic event. The upper unit contains the least altered rocks of the Cleopatra Member and the bulk of the sixth alteration type, designated H. The rocks included within H-type alteration have disseminated hematite and/or hematitic chert veining.Whole-rock and mineral geochemistry of the lower unit may be used to establish position within the palcohydrothermal system. The distal area of moderate alteration (B1) contains samples enriched in MgO, slightly depleted in alkalies, and having ratios of Fe203(t, ,/Fe203•,, • + MgO for whole rocks and Fe(total)/Fe(total) + Mg for chlorites that are oa oa) low relative to other Cleopatra Member samples. These attributes are suggestive of the lowtemperature seawater-rock interaction expected in the domain of fluid recharge. Rocks of alteration type C experienced significant additions of iron and magnesium, and losses of CaO, Na20, and K20, presumed to reflect alteration in the main discharge conduit for the hydrothermal fluid. Chlorite and whole-rock iron to iron-plus-magnesium ratios decrease within the area of alteration type C toward the sediment-water interface. This is consistent with mixing of an evolved ore-forming fluid with seawater in the upper levels of the area of alteration type C. Samples from the area of alteration type B2, which is intermediate between the recharge (B1) and discharge areas (C), are greatly depleted in CaO and Na20, and are enriched in iron. Alteration types S1 and S2 are interpreted to reflect localized sites of fluid discharge where SiO2 and K20 have been added and other major elements, except for A1203, have been removed.Whole-rock and mineral chemistry of the alteration types record progressive changes in the hydrothermal fluid from seawater to an ore-forming f...

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“…56, no. 2, 2006 Hydrothermal Alteration of Oman Ophiolite Extrusives 169 Most of the REE (rare earth elements) and HFSE (high field strength elements) have been found to be immobile in hydrothermal alteration processes associated with massive sulfide deposition (Finlow-Bates and Stumpfl, 1981;Vance and Condie, 1987;MacLean and Kranitoids, 1987). The lavas in Ghuzayn area were discriminated into andesitic and basaltic lavas.…”

Section: Igneous Mineralogy and Geochemistrymentioning

confidence: 99%

Hydrothermal Alteration of Oman Ophiolite Extrusives in Ghuzayn Area

et al. 2006

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Convective circulation of seawater through oceanic crust at mid-oceanic ridges (MOR), on ridge flanks and at back arc basins has wide effects on heat transport, chemical and isotopic compositions of oceanic crust and seawater, mineralization in the crust and on the physical properties of the oceanic basement. The mineralization which occurred in the oceanic crust was resulted by metals leached from large volumes of altered crust at various depths from the surface of hydrothermal circulation (Hannington et al., 1995). Therefore, the study on the ophiolites which are accessible fragments of oceanic crust exposed on land and studied as analogues for tectonic, magmatic and hydrothermal processes occurring at modern MORs and back arc basins that are much more difficult to sample and examine directly, has been used to model chemical and isotopic fluxes between seawater and the ocean crust during hydrothermal alteration and the effect on the compositions of seawater and the crust (e.g., Gregory and Taylor, 1981;Bickle and Teagle, 1992;Alt, 1994).Mineralization and massive sulfide deposits in ophiolites are also cited as analogues of black smokers forming on modern oceanic crust (Hannington et al., 1995). At the same time, the alteration patterns documented for modern oceanic crust and ophiolites record the short and long time-integrated effects of fluid-rock interaction related to the oceanic hydrothermal systems.Geological, geophysical and drilling surveys were applied to investigate the mineralizations in the explo- RESOURCE GEOLOGY, vol. 56, no. 2, 167-182, 2006 167 Abstract: The hydrothermal alteration in Ghuzayn Volcanics was associated with mineralization and accumulation of three massive sulfide deposits. The Ghuzayn Volcanics were discriminated into basaltic and andesitic lavas. The crossplots of Zr versus Nb, Y, Hf, La and Lu show that they fall in the same linear fractionation trends with more evolved affinities in the andesitic lavas compared to the less evolved affinities in the basaltic lavas. The immobile trace element contents of the Ghuzayn Volcanics show that they are of oceanic to continental tholeiitic affinity which fall in the fields of back-arc basin basalt, N-MORB and island arc tholeiite all meet and match with the field of the Lau-Tonga back-arc basin lavas. The ore-body No. 2 is underlain by a zone of intense argillization and silicification which are so-called alteration pipe as in some of the Cyprus-type massive sulfide deposits. The alteration in the proximity of the ore-body No. 2 is characterized by a zone of epidotization and slight silicification and sulfide disseminations, and surrounded by another zone of slight silicification and sulfide dissemination in the outermost rim around the ore-body No. 2. The alteration zones in the proximity of the ore-body No. 2 were divided into Zones I and II based on the abundance of the secondary minerals in the altered basaltic lavas. The Zone I is located in the most northern upper part of the ore-body No. 2 and characterized by corrensite, sa...

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Geochemistry of footwall alteration associated with the early Proterozoic United Verde massive sulfide deposit, Arizona

Cited by 23 publications

References 0 publications

The mineral chemistry of hydrothermally altered and metamorphosed wall-rocks at the Stollberg Fe-Pb-Zn-Mn(-Ag) deposit, Bergslagen, Sweden

The mineral chemistry of hydrothermally altered and metamorphosed wall-rocks at the Stollberg Fe-Pb-Zn-Mn(-Ag) deposit, Bergslagen, Sweden

Stratigraphy and alteration of the host rocks, United Verde massive sulfide deposit, Jerome, Arizona

Hydrothermal Alteration of Oman Ophiolite Extrusives in Ghuzayn Area

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