The Role of Bimodal Magmatism in Seafloor Massive Sulfide (SMS) Ore-forming Systems at the Middle Okinawa Trough, Japan

Yamasaki, Toru

doi:10.1007/s12601-018-0031-1

Cited by 11 publications

(2 citation statements)

References 77 publications

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“…The well‐documented Daly Gap (Daly, 1914) describes an apparent dearth of intermediate composition rocks, and is collectively observed in all 586,000 metamorphic and igneous samples in the Earthchem.org database. Thermodynamic instability of intermediate compositions (Daly, 1914; Dufek & Bachmann, 2010) and liquid immiscibility (Charlier et al., 2011; Reubi & Blundy, 2009), among other hypotheses (Jackson et al., 2018; Yamasaki, 2018), have been proposed to explain the gap. These hypotheses primarily revolve around the temperature and timing of melt injections, magmatic buoyancy, and/or the stability range of a melt or crystal slush to produce bimodal, intra‐crustal differentiation.…”

Section: Major Element Compositionsmentioning

confidence: 99%

A Geochemical Review of Amphibolite, Granulite, and Eclogite Facies Lithologies: Perspectives on the Deep Continental Crust

Sammon

McDonough

2021

JGR Solid Earth

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Debate abounds regarding the composition of the deep (middle + lower) continental crust. Exhumed medium‐ and high‐grade metamorphic rocks, which range in composition from mafic to felsic, provide information about the bulk composition of the deep crust. This study presents a global compilation of geochemical data on amphibolite (n = 6,500), granulite (n = 4,000), and eclogite (n = 200) facies lithologies and quantifies trends, uncertainties, and sources of bias in the deep crust sampling. The continental crust's Daly Gap is well documented in amphibolite and most granulite facies lithologies. Igneous differentiation processes likely control the compositional layering in the crust. Al2O3, Lu, and Yb vary little from top to bottom of the crust. In contrast, SiO2, light rare earth elements, Th, and U show a wider range of abundances throughout. Because of oversampling of mafic lithologies, our predictions are a lower bound on middle crustal composition. Additionally, the distinction between granulite facies terrains (intermediate SiO2, high heat production, high incompatibles) or granulite facies xenoliths (low SiO2, low heat production, low incompatibles) as being the best analogs of the deep crust remains disputable. We have incorporated both rock types, along with amphibolite facies lithologies, to define a deep crustal composition that approaches 57.6 wt.% SiO2. This number, however, represents a compositional middle ground; the shallower parts of the deep crust (middle crust) resemble quartz monzonite while the deepest portions (lower crust) more resemble a Ca‐rich monzonite. Future studies should analyze more closely the depth dependent trends in deep crustal composition to develop composition models that are not limited to a three‐layer crust.

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Section: Major Element Compositionsmentioning

confidence: 99%

A Geochemical Review of Amphibolite, Granulite, and Eclogite Facies Lithologies: Perspectives on the Deep Continental Crust

Sammon

McDonough

2021

JGR Solid Earth

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“…However, Up until now, knowledge of the internal structure of SMS deposits is based mainly on drilling results and is very scarce compared to investigations of the internal structure of land deposits [2]. There are data from the International Ocean Discovery Program (IODP), BLUE MINING and Nautilus Minerals which present the 3rd dimension of SMS deposits related to basalt hosted within MAR and arc-back-arc settings [3][4][5][6][7][8][9]. However, there is no direct information about internal structure for ultramafic-hosted deposits Geophysical data that can provide indirect information about this issue are also rare for them [10].…”

Section: Introductionmentioning

confidence: 99%

New Data for the Internal Structure of Ultramafic Hosted Seafloor Massive Sulfides (SMS) Deposits: Case Study of the Semenov-5 Hydrothermal Field (13°31′ N, MAR)

Firstova

Cherkashov²,

Stepanova³

et al. 2022

Minerals

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The internal structure of Seafloor Massive Sulfides (SMS) deposits is one of the most important and complex issues facing the study of modern hydrothermal ore systems. The Semenov-5 hydrothermal field is a unique area where mass wasting on the slope of the oceanic core complex (OCC) structure exposes the subsurface portion of the deposit and offers an exceptional opportunity to observe massive sulfides that have formed not only on the seafloor but in sub-seafloor zones as well. This paper examines the internal structure of the OCC-related Semenov-5 hydrothermal field along with analysis of the mineralogy and chemistry of different parts of sulfide deposit. The seafloor deposit is comprised of pyrite, marcasite, hematite, goethite, lepidocrocite, rare pyrrhotite, isocubanite and Co-rich pyrite. Sulfide chemistry indicates the prevailing influence of ultramafics on their composition irrespective of the spatial relation with basalt lavas. Sub-seafloor mineralization is associated with ultramafic rocks and is represented by massive and disseminated sulfides. Pyrrhotite, isocubanite, pyrite, chalcopyrite, Co-rich pyrite, quartz with rutile, quarts with hematite and Cr-spinels are fixed in massive subseafloor mineralization. The presence of Cr-spinels as well as a very high Cr content are regarded as indicators of the metasomatic nature of this part of the deposit that had formed as a result of ultramafic replacement. As a result, three zones of a hydrothermal ore-forming system have been described: massive sulfides precipitated from hot vents on the surface of the seafloor, massive sulfides formed due to replacement of ultramafics below the seafloor and disseminated sulfide mineralization-filled cracks in hosted rocks which have formed stockwork around metasomatic massive sulfides. Despite differences in the mineral and geochemical composition of sub-seafloor and seafloor mineralization, all minerals subject to the sample formed as a consequence of fluid circulation in ultramafic rocks and were linked by a common ore-forming process.

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A Geochemical Review of Amphibolite, Granulite, and Eclogite Facies Lithologies: Perspectives on the Deep Continental Crust

Sammon

McDonough

2022

Preprint

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The Role of Bimodal Magmatism in Seafloor Massive Sulfide (SMS) Ore-forming Systems at the Middle Okinawa Trough, Japan

Cited by 11 publications

References 77 publications

A Geochemical Review of Amphibolite, Granulite, and Eclogite Facies Lithologies: Perspectives on the Deep Continental Crust

A Geochemical Review of Amphibolite, Granulite, and Eclogite Facies Lithologies: Perspectives on the Deep Continental Crust

New Data for the Internal Structure of Ultramafic Hosted Seafloor Massive Sulfides (SMS) Deposits: Case Study of the Semenov-5 Hydrothermal Field (13°31′ N, MAR)

A Geochemical Review of Amphibolite, Granulite, and Eclogite Facies Lithologies: Perspectives on the Deep Continental Crust

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