Serpentinization history of the Río Guanajibo serpentinite body, Puerto Rico

Roehrig, E.; Laó‐Dávila, Daniel A.; Wolfe, Amy

doi:10.1016/j.jsames.2015.06.004

Cited by 4 publications

(2 citation statements)

References 77 publications

(101 reference statements)

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“…Serpentinization along MORs is the result of reactions between peridotite and seawater/hydrothermal fluids, a process that forms serpentine minerals (lizardite, antigorite, and chrysotile) and subordinate amounts of opaque minerals (e.g., magnetite, haematite, sulfide, and Fe–Ni alloys; Andreani et al, 2007; Mével, 2003; O'Hanley, 1992; Plümper et al, 2012; Roehrig et al, 2015). Serpentinization is controlled mainly by temperature and seawater flux.…”

Section: Discussionmentioning

confidence: 99%

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

et al. 2022

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To date, discovered ultramafic-hosted seafloor massive sulfide (UM-SMS) deposits are rare, remain poorly understood in terms of their genesis, and typically form along slow-and ultraslow-spreading mid-oceanic ridges. The Tianzuo hydrothermal field (THF) is the only UM-SMS deposit identified so far along the ultraslow-spreading South-west Indian Ridge (SWIR). This study presents new detailed mineralogical and S-C isotopic data for serpentinized peridotite, gabbro, serpentinite, and sulfide ore samples from the THF and to provide new insights into the processes that formed the deposit. Chromium-reduced sulfur (CRS) and sulfate-sulfur (SS) in samples of serpentinized peridotite have positive δ 34 S values (up to 10.22‰ and 20.67‰, respectively). The CRS formed through thermochemical reduction of seawater sulfate during reactions between seawater and ultramafic rocks, whereas the SS most likely occurred as dissolved sulfate phases in seawater occupying the pore space of serpentinized peridotite after exposure at the seafloor. The serpentinite samples contain SS with δ 34 S values of 19.21‰-20.9‰, indicating infiltration by seawater that led to the deposition of seawater sulfate. The sulfide ores have acid-volatile sulfur (AVS), CRS, and SS δ 34 S values of 10.99‰-12.07‰, 2.34‰-10.98‰, and À4.13‰ to 2.76‰, respectively, indicating that the AVS and CRS within the samples are dominated by sulfur reduced from seawater sulfate (e.g., anhydrite) and leached from the surrounding wall rocks, although the re-oxidization of microbial-reduced sulfur most likely generated the sulfate with low and negative δ 34 S values. The total carbon and total organic carbon δ 13 C values of the THF samples are negative and range from À21.99‰ to À0.34‰ and À26.7‰ to À21.02‰, respectively, further suggesting that the samples record microbial activity. Gabbro samples have strongly negative AVS (À10.69‰) and CRS (À7.2‰) δ 34 S values, indicating that microbial-reduced sulfur derived from shallow levels in the crust was incorporated into the hydrothermal system that circulated through the deeper-seated gabbroic units. Our results suggest

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Section: Discussionmentioning

confidence: 99%

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

et al. 2022

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“…The Monte del Estado massif, the largest and northernmost belt, consists predominantly of peridotites (Marchesi et al 2011; Laó-Dávila, Llernadi-Román & Anderson, 2012). The middle Rio Guanajibo belt also comprises mainly peridotites (Hess & Otalora, 1964; Roehrig, Laó-Dávila & Wolfe, 2015). The southernmost belt of the Bermeja Complex contains blocks (up to several hundred metres in size) of amphibolite, metabasalt, basalt and chert within the serpentinized peridotite (Mattson, 1960; Schellekens, 1998 b ).…”

Section: General Geologymentioning

confidence: 99%

Peridotites and basaltic rocks within an ophiolitic mélange from the SW igneous province of Puerto Rico: relation to the evolution of the Caribbean Plate

Franqui

Choi

Lee³

2016

Geol. Mag.

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The geology of Puerto Rico is divided into three regions: the north, central and SW igneous provinces. Characterized by its Jurassic ophiolitic mélange basement, lithology of the SW Igneous Province (SIP) is not related to either of the other two provinces. The ophiolitic mélange is exposed in three peridotite belts: Monte del Estado, Rio Guanajibo and Sierra Bermeja. We present geochemical data to identify the tectonic setting of the SIP peridotite formation and its relation to the evolution of the Caribbean Plate. Comparisons of spinel Cr no. (13–21), Mg no. (63.3–69.6) and TiO2suggest an abyssal peridotite origin; however, only Sierra Bermeja presents high TiO2characteristics of a mid-ocean-ridge-basalt- (MORB-) like melt reaction. Temperatures determined with two-pyroxene geothermometers indicated a cold thermal regime ofc. 800–1050°C, with characteristics of large-offset transform fault abyssal peridotites. The geochemistry and Sr–Nd–Hf–Pb isotopic compositions of basalts within the mélange were also analysed. Las Palmas amphibolites exhibited normal-MORB-like rare earth element (REE) and trace-element patterns, whereas metabasalts and Lower Cajul basalts exhibited island-arc tholeiitic-like patterns. Highly radiogenic Sr isotopes (0.70339–0.70562) of the basalts suggest seawater alteration; however, Pb–Pb and Nd–Hf isotope correlations represent the primary compositions of a Pacific/Atlantic MORB source for the amphibolites, metabasalts and Lower Cajul basalts. We propose that the SIP ophiolitic mélange was formed along a large-offset transform fault, which initiated subduction and preserved both proto-Pacific and proto-Caribbean lithospheric mantle. Younger Upper Cajul basalts exhibited enriched-MORB-like geochemical and isotopic signatures, which can be attributed to a tectonized Caribbean ocean plateau.

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Serpentinization and its implications for ultramafic-hosted sulfide mineralization: A case study at the Tianzuo hydrothermal field, 63.5°E, Southwest Indian Ridge

et al. 2023

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Serpentinization history of the Río Guanajibo serpentinite body, Puerto Rico

Cited by 4 publications

References 77 publications

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

Peridotites and basaltic rocks within an ophiolitic mélange from the SW igneous province of Puerto Rico: relation to the evolution of the Caribbean Plate

Serpentinization and its implications for ultramafic-hosted sulfide mineralization: A case study at the Tianzuo hydrothermal field, 63.5°E, Southwest Indian Ridge

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