Mantle flow
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The spreading of the East Vietnam Sea (EVS, also known as Bien Dong, or the South China Sea), leading to the occurrence of syn-spreading (33-16 Ma) and post-spreading (< 16 to present) volcanism. Syn-spreading magma making up thick layers of tholeiitic basalt with a geochemical composition close to the refractory and depleted mid-ocean ridge basalt (MORB) is mainly distributed inside the EVS basin.
25p vipagani 24-10-2022 10 2 Download
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These geochemical traits point to the adakite-like affinity for Pertek andesite-dacite porphyries, however, they present some geochemical characteristics of both oceanic slab-derived and continental crust-derived adakites and show a dual character. Enrichment in K2 O, Th, Rb, and Hf in these adakitic porphyries is mostly associated with the crust-derived terrigenous sediments during active subduction, before the Early Miocene.
39p tanmocphong 29-01-2022 7 0 Download
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In the Gandom Beryan area, basanitic lava flows erupted from fractures in the Nayband fault zone and formed an area of about 300 km2 of basanitic rocks in the western part of the Lut Block. Olivine and clinopyroxene are the major phenocrysts in a microlitic groundmass for these basanitic rocks.
18p viminotaur2711 30-10-2019 17 2 Download