Subduction zone geochemistry

Zheng, Yong Fei

doi:10.1016/j.gsf.2019.02.003

Cited by 337 publications

(81 citation statements)

References 337 publications

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“…Indeed, according to our results, crystalline plagioclases composing a major portion of a subducting crust may exist under the P-T conditions of (ultra)cold subducting slabs [41][42][43] , as shown in Fig. 4.…”

Section: Discussionsupporting

confidence: 68%

Polymorphism of feldspars above 10 GPa

et al. 2020

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Feldspars are rock-forming minerals that make up most of the Earth's crust. Along the mantle geotherm, feldspars are stable at pressures up to 3 GPa and may persist metastably at higher pressures under cold conditions. Previous structural studies of feldspars are limited tõ 10 GPa, and have shown that the dominant mechanism of pressure-induced deformation is the tilting of AlO 4 and SiO 4 tetrahedra in a tetrahedral framework. Herein, based on results of in situ single-crystal X-ray diffraction studies up to 27 GPa, we report the discovery of new high-pressure polymorphs of the feldspars anorthite (CaSi 2 Al 2 O 8), albite (NaAlSi 3 O 8) , and microcline (KAlSi 3 O 8). The phase transitions are induced by severe tetrahedral distortions, resulting in an increase in the Al and/or Si coordination number. High-pressure phases derived from feldspars could persist at depths corresponding to the Earth upper mantle and could possibly influence the dynamics and fate of cold subducting slabs.

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Section: Discussionsupporting

confidence: 68%

Polymorphism of feldspars above 10 GPa

et al. 2020

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“…The presence of negative Eu and Sr anomalies indicate a shallow crustal source for the granites (Upadhyay, 2019). In the primitive mantle normalized trace element plot, there is a large depletion in Nb, and an enrichment in Pb (Zheng, 2019). The depletion in Nb indicates a subduction zone setting because it is a HFSE.…”

Section: Major/trace Elementsmentioning

confidence: 99%

Magmatic and Tectonic Setting of Archean Granitoids in the Southeastern Singhbhum Craton, India: Developing constraints with major and trace element geochemistry and geochronology

Banks

2020

UFJUR

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The Singhbhum craton is one of five Archean nuclei comprising Peninsular India. It is a composite Archean block that includes the Older Metamorphic Group, the Older Metamorphic Tonalite Gneisses, the Singhbhum Granite, and the Iron Ore Group as its major units. The ages of these components range from ~3.5 to ~3.1 Ga, although overlapping ages and similar rock types confound their genetic relationships. Plutonic felsic rocks from the southeastern Singhbhum craton (BK1: a foliated tonalite, KP1: a non-foliated granite, and SG14: a non-foliated granite) yield U-Pb (zircon) ages of 3321 ± 2 Ma (BK1), 3301 ± 1 Ma (KP1), and 3261 ± 1 Ma (SG14) that coincide with a pulse of Singhbhum Granite emplacement at 3.27 to 3.33 Ga. REE patterns and tectonic discrimination diagrams based on major and trace element ratios suggest a subduction zone setting for these rocks. We report major and trace element data for and compare them to previous works in order to characterize the Archean felsic plutonic history of the craton.

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“…As a result of hydrothermal alteration by seawater, igneous oceanic crust acquires variably elevated abundances of LILE and Pb relative to N-MORB, so seafloor sediments show significant enrichments in LILE, Pb, LREE, Nb and Ta compared with MORB, despite the Nb-Ta trough in the diagram ( Fig. 7b; Zheng, 2019). The gabbro and basalts exhibit variable contents of , Nb (2.04-6.85 ppm), Ta (0.13-2.03 ppm) and Hf (1.58-4.93 ppm), which are close to those of typical modern oceanic arcs (Sun & McDonough, 1989;Stolz et al 1996;Fliedner & Klemperer, 2000).…”

Section: B1 Gabbro and Basaltsmentioning

confidence: 99%

A mid-Palaeozoic ocean–continent transition in the Mazongshan subduction–accretion complex, Beishan, NW China: new structural, chemical and age data constrain the petrogenesis and tectonic evolution

et al. 2020

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Accretionary orogens contain key evidence for the conversion of oceanic to continental crust. The late tectonic history and closure time of the Palaeo-Asian Ocean are recorded in the Mazongshan subduction–accretion complex in the southern Beishan margin of the Central Asian Orogenic Belt. We present new data on the structure, petrology, geochemistry and zircon U–Pb isotope ages of the Mazongshan subduction–accretion complex, which is a tectonic mélange with a block-in-matrix structure. The blocks are of serpentinized peridotite, basalt, gabbro, basaltic andesite, chert and seamount sediments within a matrix that is mainly composed of fore-arc-trench turbidites. U–Pb zircon ages of two gabbros are 454.6 ± 2.5 Ma and 434.1 ± 3.6 Ma, an andesite has a U–Pb zircon age of 451.3 ± 3.5 Ma and a tuffaceous slate has the youngest U–Pb zircon age of 353.6 ± 5.1 Ma. These new isotopic ages, combined with published data on ophiolitic mélanges from central Beishan, indicate that the subduction–accretion of Beishan in the southernmost Central Asian Orogenic Belt lasted until Late Ordovician – Early Carboniferous time. Structure and age data demonstrate that the younging direction of accretion was southwards and that the subduction zone dipped continuously to the north. Accordingly, these results record the conversion of oceanic to continental crust in the southern Beishan accretionary collage.

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Subduction zone geochemistry

Cited by 337 publications

References 337 publications

Polymorphism of feldspars above 10 GPa

Polymorphism of feldspars above 10 GPa

Magmatic and Tectonic Setting of Archean Granitoids in the Southeastern Singhbhum Craton, India: Developing constraints with major and trace element geochemistry and geochronology

A mid-Palaeozoic ocean–continent transition in the Mazongshan subduction–accretion complex, Beishan, NW China: new structural, chemical and age data constrain the petrogenesis and tectonic evolution

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