Tectonic setting and mineralogical and geochemical zonation in the Snake Pit sulfide deposit (Mid-Atlantic Ridge at 23 degrees N)

Fouquet, Yves; Wafik, Amina; Cambon, Pierre; Mével, Catherine; Meyer, G.; Gente, Pascal

doi:10.2113/gsecongeo.88.8.2018

Cited by 174 publications

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“…More importantly, magmatic activity along the basin rift zone provided the necessary heat source for the convection of hydrothermal fluids, which delivered metals from depth and deposited them around or in the vicinity of hydrothermal vents and in the subsurface (e.g., Knott et al, 1998). The morphology, types of metals, sandy texture of the ore, sharp contacts between the silica and the metals, silica in between the metal grains, and pillow basalt-chert host rocks of the VMS deposits in the Antique ophiolite collectively indicate their formation similar to the mineralization around and below actual oceanic hydrothermal vents (e.g., Fouquet et al, 1993;Peter and Scott, 1999;Knott et al, 1998), except that the Antique deposits were affected by post-mineralization tectonic deformation. Interestingly, most of the VMS deposits in Antique are associated with the intermediate MORB-IAB Bongbongan group (Fig.…”

Section: Implications To Vms and Chromitite Depositsmentioning

confidence: 99%

Petrochemical Investigation of the Antique Ophiolite (Philippines): Implications on Volcanogenic Massive Sulfide and Podiform Chromitite Deposits

Tamayo

Yumul²,

Maury

et al. 2001

Resource Geology

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IntroductionVolcanogenic massive sulfides (VMS) and podiform chromitites commonly occur in ophiolite complexes. The VMS bodies are found in or near the contact of the pillow basalts and the overlying sedimentary rocks. A common feature of these deposits, particularly those relatively unaffected by tectonic deformation, is their mound-like morphology and subsurface stockwork-type mineralization, which are reminiscent of the structure of hydrothermal vents and their associated metal accumulations observed in modern mid-oceanic ridges (Hannington et al., 1995;Knott et al., 1998) and backarc basin rifts (Halbach et al., 1989;Binns and Scott, 1993). The podiform chromitites, on the other hand, occur in the transition zone dunites and residual upper mantle sequences of ophiolite complexes (Roberts, RESOURCE GEOLOGY, vol. 51, no. 2, 145-164, 2001 145 (IAB). The residual upper mantle sequence is harzburgitic and generally more depleted than the upper mantle underlying modern mid-oceanic ridges. Calculations using whole-rock and mineral compositions show that they can represent the residue of a fertile mantle source, which have undergone degrees of partial melting ranging from 9-22.5 %. Some of the mantle samples display chondrite-normalized REE and extended multi-element patterns suggesting enrichments in LREE, Rb, Sr and Zr, which are comparable to those found in fore-arc peridotites from the Izu-Bonin-Mariana (IBM) arc system. The Antique ultramafic rocks also record relatively oxidizing mantle conditions (∆log f O 2 (FMQ)=0.9-3.5). As a whole, the ophiolite probably represents an agglomeration of oceanic ridge and fore-arc crust fragments, which were juxtaposed during the Miocene collision of the PMB and the NPB. The intrusion of the serpentinites might be either coeval or subsequent to the accretion of the oceanic crust onto the fore-arc.Volcanogenic massive sulfide (VMS) deposits occur either in or near the contact between the pillow basalts and the overlying sediments or interbedded with the sediments. The morphology of the deposits, type of metals, ore texture and the nature of the host rocks suggest that the formation of the VMS bodies was similar to the accumulation of metals around and in the subsurface of hydrothermal vents observed in modern mid-oceanic ridge and back-arc basin rift settings. The podiform chromitites occur as pods and subordinate layers within totally serpentinized dunite in the residual upper mantle sequence. No large coherent chromitite deposit was found since the host dunitic rocks often occur as blocks within the serpentinites. It is difficult to evaluate the original geodynamic setting of the mineralized bodies since the chemistry of the host rocks were considerably modified by alteration during their tectonic emplacement. A preliminary conclusion for Antique is that the VMS is apparently associated with a primitive tholeiitic intermediate MORB-IAB volcanic suite, the chemistry of which is close to the calculated composition of the liquid that coexisted with the podiform chromitites.

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Section: Implications To Vms and Chromitite Depositsmentioning

confidence: 99%

Petrochemical Investigation of the Antique Ophiolite (Philippines): Implications on Volcanogenic Massive Sulfide and Podiform Chromitite Deposits

Tamayo

Yumul²,

Maury

et al. 2001

Resource Geology

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“…Active chimneys with beehive-type diffuser tops (cf. Fouquet et al 1993) are located immediately south of this site.…”

Section: Geological Settingmentioning

confidence: 99%

Geochemistry and Mineralogy of Gold-Rich Hydrothermal Precipitates From the Eastern Manus Basin, Papua New Guinea

Moss

Scott

2001

The Canadian Mineralogist

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Three of the five hydrothermal vent fields currently known in the Manus back-arc basin of Papua New Guinea are enriched in gold. Samples of precipitates from the PACMANUS and Susu Knolls hydrothermal fields in eastern Manus Basin contain up to 56.8 ppm gold, and average 11.3 ± 13 (1) ppm (n = 103). Chimney samples dominated by sphalerite, barite and chalcopyrite have significantly higher contents of gold than sulfide-poor samples. Gold in the sulfide chimneys occurs as micrometric grains of silver-poor (1.4 to 4.2 wt.% Ag) native gold in three distinct associations. In copper-rich chimney samples, gold occurs as inclusions in chalcopyrite associated with tennantite, bornite and covellite. In zinc-rich chimney samples, gold is present mainly as inclusions in tennantite associated with chalcopyrite and sphalerite. A high activity of sulfur is indicated for the gold-rich eastern Manus Basin precipitates by the sulfide assemblages, the low iron content of sphalerite (average = 2.3 ± 3 mole % FeS), and the silver-poor nature of gold grains. Evaluation of possible complexes of gold indicates that AuHS° is the dominant complex, which is consistent with the high activity of sulfur in the hydrothermal system. According to available experimental data, AuHS° is the dominant complex up to 325°C. This complex thus is the only one required for gold enrichment in both the Zn-Au and the Cu-Au associations. Gold transport as the AuHS° complex is likely to be equally important in other seafloor hydrothermal systems with acidic end-member hydrothermal fluids.

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“…Most hydrothermal sites are basalt-hosted, with seafloor venting corresponding to the visible part of a complex and vigorous fluid circulation system active at the sub-surface. A typical modern seafloor sulphide deposit encompasses a consolidated sulphide mound, underlain by a sub-seafloor stockwork and covered by active and inactive chimney structures, hydrothermal crusts, metalliferous sediments and sulphide debris (Goodfellow and Franklin 1993;Fouquet et al 1993aFouquet et al , 1993bRona et al 1993;Alt 1995;Hannington et al 1995;Herzig and Hannington 1995;Humphries et al 1995;Fouquet et al 1996). These features, commonly found in modern seafloor deposits, correlate well with those of ancient volcanichosted massive sulphide (VMS) deposits (Doyle 2003).…”

Section: Introductionmentioning

confidence: 99%

Mineralogy, geochemistry, and Nd isotope composition of the Rainbow hydrothermal field, Mid-Atlantic Ridge

et al. 2006

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Petrological, geochemical and Nd-isotopic analyses have been carried out on rock samples from the Rainbow vent field to assess the evolution of the hydrothermal system. The Rainbow vent field is an ultramafic-hosted hydrothermal system located on the Mid-Atlantic Ridge, characterized by vigorous high-temperature venting (~365ºC) and unique chemical composition of fluids: high chlorinity, low pH and very high Fe and REE contents (Douville et al. 2002). Serpentinisation has occurred under a low-temperature (<270ºC) retrograde

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Tectonic setting and mineralogical and geochemical zonation in the Snake Pit sulfide deposit (Mid-Atlantic Ridge at 23 degrees N)

Cited by 174 publications

References 0 publications

Petrochemical Investigation of the Antique Ophiolite (Philippines): Implications on Volcanogenic Massive Sulfide and Podiform Chromitite Deposits

Petrochemical Investigation of the Antique Ophiolite (Philippines): Implications on Volcanogenic Massive Sulfide and Podiform Chromitite Deposits

Geochemistry and Mineralogy of Gold-Rich Hydrothermal Precipitates From the Eastern Manus Basin, Papua New Guinea

Mineralogy, geochemistry, and Nd isotope composition of the Rainbow hydrothermal field, Mid-Atlantic Ridge

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