Geochemistry, zircon U-Pb geochronology and Sr-Nd-Hf isotopic composition of the Cha Val plutonic rocks in central Vietnam: Implications for Permian-Triassic Paleo-Tethys subduction-related magmatism

together with abundant Permian-Triassic magmatic rocks. This magmatic complex provides important information to reconstruct the tectonic evolution of the Indochina block and surrounding areas. The Cha Val plutonic rocks mainly comprise diorite, quartz diorite, and granodiorite. Geochemically, they are metaluminous with low A/CNK (0.49 to 1.16 with an average of 0.85), medium to high K, low to medium SiO2, and Na2O/K2O>1. Trace and rare earth element compositions display enrichment in Cs, U, Pb, and Nd, but depletion in Ba, Nb, Ta, P, Eu, and Ti, similar to those of continental arc-related magmas. Rock-forming minerals of the Cha Val plutonic rocks are characterized by abundant hornblende. All observed petrographical and geochemical characteristics suggest that the Cha Val plutonic rocks are typical for I-type affinity generated from a subduction regime. LA-ICP-MS U-Pb zircon analyses of three representative samples yielded their crystallization ages between 258.0 Ma and 248.9 Ma, temporally coeval with Late Permian-Early Triassic magmatism previously reported in the Truong Son belt. The (87Sr/86Sr)i ratios (0.7081 to 0.7244), negative whole-rock εNd(t) values (-4.5 to -2.9), zircon εHf(t) values (-1.04 to 2.71), and whole-rock Nd and zircon Hf model ages (TDM2) (1394 Ma to 1111 Ma) indicate that the Cha Val plutonic rocks are derived from melting of Mesoproterozoic crustal materials with a minor contribution of mantle-derived melt. Together with other Permian-Triassic magmatic complexes along the Song Ma suture zone and the Truong Son Belt, the Cha Val plutonic rocks are a representative of magmatism associated with the subduction-collision that amalgamated the South China and Indochina blocks after the closure of a branch of Paleo-Tethys along the Song Ma suture zone during the Late Permian-Early Triassic Indosinian orogeny.

Supplemental Material: The Middle-Late Cretaceous Zagros ophiolites, Iran: Linking of a 3000 km swath of subduction initiation fore-arc lithosphere from Troodos, Cyprus to Oman

Table S1: Zircon O and Lu-Hf isotopic composition of the Zagros inner-belt and outer-belt ophiolitic rocks; Table S2: Whole rock major and trace elements analysis of the Zagros inner-belt and outer-belt ophiolitic rocks; Table S3: LA-ICP-MS U-Pb analyses of zircons from the Zagros inner-belt and outer-belt ophiolites; Table S4: SIMS U-Pb analyses of zircon from the Zagros inner-belt and outer-belt ophiolites; Appendix A.

Supplemental Material: The Middle-Late Cretaceous Zagros ophiolites, Iran: Linking of a 3000 km swath of subduction initiation fore-arc lithosphere from Troodos, Cyprus to Oman

Table S1: Zircon O and Lu-Hf isotopic composition of the Zagros inner-belt and outer-belt ophiolitic rocks; Table S2: Whole rock major and trace elements analysis of the Zagros inner-belt and outer-belt ophiolitic rocks; Table S3: LA-ICP-MS U-Pb analyses of zircons from the Zagros inner-belt and outer-belt ophiolites; Table S4: SIMS U-Pb analyses of zircon from the Zagros inner-belt and outer-belt ophiolites; Appendix A.

High-precision geochronology requires that ultrafast mantle-derived magmatic fluxes built the transcrustal Bear Valley Intrusive Suite, Sierra Nevada, California, USA

The Bear Valley Intrusive Suite (BVIS), located in the southernmost Sierra Nevada Batholith (SNB; California, USA) exposes a transcrustal magma system consisting of lower-crustal gabbros and volumetrically extensive middle- and upper-crustal tonalites. New chemical abrasion–isotope dilution–thermal ionization mass spectrometry U-Pb geochronology shows that the bulk of this ca. 100 Ma magmatic system crystallized in 1.39 ± 0.06 m.y. and was constructed with ultrahigh magmatic fluxes (∼250 km3/km/m.y.). This magmatic flux is roughly a factor of three greater than estimates for the SNB-wide flux during the Late Cretaceous flare-up, showing that individual magmatic systems can be constructed at extremely rapid rates. Further, the Hf isotopic composition of the BVIS (εHfi ∼–2 to +4) only allows for limited (∼25%) crustal assimilation. Our results show that the high magmatic fluxes recorded in the BVIS were dominantly derived from the mantle, and that “flare-up”–like local magmatic fluxes can be produced without extraordinary assimilation of crustal material.