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[Display omitted] • The composite Lailishan pluton was emplaced during 54–52 Ma. • Syenogranite and monzogranite derived from partial melting of metabasalts. • Diabase formed from lithospheric mantle metasomatized by slab-derived fluids. • Syenogranite provided ore-forming materials related to tin deposit. • Eocene magmatic activities related to the slab rollback of the Neo-Tethys. Granitoids are the major building blocks of Earth's continental crust, and provide important insights into the evolution of continental crust and related mineral resources. Here we investigate the Eocene composite Lailishan pluton in the western Tengchong Block based on studies of petrology, mineral chemistry, zircon U-Pb-Hf isotopes, whole-rock geochemistry, and Sr-Nd isotope data to understand the petrogenesis and tectonic implications. The pluton is composed of monzogranite, syenogranite and abundant microgranitoid enclaves (ME) in the monzogranite. The zircon U-Pb data show similar rock formation ages in the range of 54–52 Ma. A diabase dyke intruded into the monzogranite at 54 Ma. The geochemical and isotopic signatures (εHf(t) of −11.6 to −3.1 and εNd(t) of −9.4 to −8.8) suggest that both the monzogranite and syenogranite were derived from the partial melting of metabasaltic rocks in the Mesoproterozoic Gaoligong metamorphic basement. The geochemical trends of the syenogranite indicate the significant fractional crystallization of biotite, plagioclase, K-feldspar, apatite, allanite and monazite, which further facilitated the enrichment of Sn in the syenogranite. The typical igneous textures, megacrysts from host granites, compositional zoning of the plagioclase and large variation of εHf(t) from −9.3 to −2.6 of the ME suggest a magma mixing and mingling process, which corresponds well with mass balance calculation using monzogranite and diabase as two endmembers. The mantle-like isotopic characteristics (εHf(t) of −2.4 to 2.0 and εNd(t) of −5.9) and low Th/La, Th/Nb and Nd/Pb ratios of the diabase dyke samples suggest the lithospheric mantle metasomatized by subducted fluids as the magma source. We propose that the slab rollback of the Neo-Tethys Ocean facilitated the interaction between crustal and mantle derived magmas generating a major pulse of Eocene magmatic activity in the Tengchong Block. [ABSTRACT FROM AUTHOR]

The Kejie pluton is located in the north of the Changning-Menglian suture zone. The rock types are mainly biotite-granite. Zircon LA-ICP-MS U-Pb dating indicates that the Kejie pluton emplaced at about 80-77 Ma, Late Cretaceous. The Kejie pluton samples are characterized by high SiO2 (71.68%-72.47%), K2O (4.73%-5.54%), total alkali (K2O + Na2O = 8.21%-8.53%), K2O/Na2O ratios (1.36-1.94) and low P2O5 (0.13%-0.17%), with A/CNK of 1.025-1.055; enriched in U, Th, and K, depleted in Ba, Nb, Sr, Ti, P and Eu. They are highly fractionated, slightly pet aluminous I-type granite. The two samples of the Kejie pluton give a large variation of εHf( t) values (-5.04 to 1.96) and Hf isotope crustal model ages of 1.16-1.5 Ga. Zircon Hf isotopes and zircon saturation temperatures of whole-rock (801°C-823°C) show that the mantle-derived materials maybe have played a vital role in the generation of the Kejie pluton. The Kejie pluton was most likely generated in a setting associated with the eastward subduction of the neo-Tethys ocean, where intrusion of mantle wedge basaltic magmas in the crust caused the anatexis of the latter, forming hybrid melts, which subsequently experienced high-degree fractional crystallization. [ABSTRACT FROM AUTHOR]

Abstract: Lincang granite is a batholith located in the Sanjiang region and is an important research subject for understanding subduction and collision during the Paleo-Tethyan period. It is widely exposed in the Lincang Terrane and extends south into Burma. Based on various petrological and geochemical investigations performed from south to north across the Lincang granite, a new set of data, which includes zircon chronological and Hf isotopic data, is presented to discuss the origin of the Lincang granite and its tectonic significance. The Lincang granite is a peraluminous, high-K calc-alkaline body with sub-parallel REE patterns and a strong negative Eu anomaly. This anomaly is characteristic of a post-collision peraluminous S-type granitic batholith. The 200–230Ma formation age of the Lincang granite was determined using LA-ICP-MS zircon U–Pb dating. Thus, it has been confirmed that the granite formed during the late Triassic period, and the formation process lasted for approximately 30Ma. Geochemical and isotopic compositions indicate that the primary magma of Lincang granite most likely originated from a crustal source, and possibly underwent an assimilation–fractionation crystallization (AFC) process during its emplacement. The Lincang granite formed during the continental collision between the Baoshan–Gengma Terrane and the Lanping–Simao Terrane after the northeast subduction of the Paleo-Tethyan Oceanic Plate. Therefore, the late Triassic Lincang granite is important evidence for the closure of the Paleo-Tethyan Ocean. [Copyright &y& Elsevier]

Fission track (FT) ages of apatite and zircon from four grantie batholiths from Lhasa and Shannan areas are measured. The FT ages of apatite range from 3.2 to 8.3 Ma, corresponding to the uplift rates of 0.12 to 0.20 mm·a[SUP-1] during this period. The uplift height is 580 m, showing that there is not large-scale rapid uplifting in southern Tibet from 3.2 to 8.3 Ma. The zircon FT ages of Lhasa batholith are 25.9 ± 1.7 and 32.7 ± 2.8 Ma, yielding an uplift rate of 0.08 mm·a[SUP-1] between 26 and 33 Ma. Combining this work with other studies, it is suggested that the average uplift rate in southern Tibet is low from the time of collision between India and Asian continents to -3 Ma. The uplift of Tibetan Plateau seems to have finished in multi-stage processes with varied rates. fission track age, uplift rate, Lhasa, Tibet [ABSTRACT FROM AUTHOR]

Abstract: The leucogranites in the Baoshan Block of the Tethyan belt in Western Yunnan, are composed mainly of two-mica granite with subordinate muscovite granite. Here we present zircon U–Pb ages from four intrusions that show ages of 448–476Ma suggesting that these rocks were emplaced during the Ordovician. The leucogranites are high-K calc-alkaline and strongly peraluminous, with K2O/Na2O>1 and A/CNK=1.12–1.54. These rocks are enriched in large-ion lithophile elements (LILEs) and light rare-earth elements (LREEs) [(La/Yb)N =1.13–32.4] and Pb, and are depleted in high field-strength elements (HFSEs). They show similar chondrite-normalized REE patterns, with negative Eu anomalies (Eu/Eu*=0.03–0.46). A wide range of zircon εHf(t) values (−9.6 to −2.6) and varying Hf-isotope crustal model ages (2.1–1.6Ga) are also observed. The geochemical signatures indicate that the leucogranites are S-type granites derived mainly from the anatexis of ancient crustal materials. The ages, geochemistry and tectonics in the Baoshan Block and the Lhasa Terrane are closely comparable, suggesting that the Baoshan Block might represent part of an Early Paleozoic magmatic arc in the Gondwana continental margin facing the proto-Tethyan Ocean. The Pinghe granites of the early phase in the Baoshan Block which are coeval with the Cambrian magmatism (ca. 492Ma) identified in the central and southern Lhasa subterranes can be interpreted as products of the slab break-off associated with the subduction of proto-Tethyan oceanic lithosphere. However, the late leucogranite stocks are analogous to the North Himalayan leucogranites, which formed in a short-lived extensional setting caused by the slab break-off associated with the subduction–collision system. [Copyright &y& Elsevier]

[Display omitted] • Monzonite was formed from melts derived from a mantle wedge after fractionation. • The adakitic features of granite are formed by amphibole-dominated fractionation. • Nenjiang ocean experienced slab rollback at ∼375 Ma, and closed at ∼320 Ma. Disputes regarding the subduction process, closure time, and the location of the Nenjiang Ocean have arisen due to limited exposure of late Paleozoic magmatic rocks in the Xing'an block. In this study, we present new zircon U-Pb age, zircon Hf isotope, zircon trace elements and whole rock geochemistry to reveal the evolution process of the Nenjiang Ocean in the late Paleozoic. The Heihe monzonite samples originated from the partial melting of a depleted mantle wedge metasomatized by subduction-related fluids and experienced fractional crystallization of plagioclase and amphibole. The Heihe granites show adakitic affinity, with low contents of compatible elements and U-shaped chondrite-normalized REEs patterns, indicating that the adakitic characteristics of the Heihe granites were formed by amphibole-dominated fractional crystallization. Geochemical modeling shows that the Heihe granite can be generated at a degree of 30–75 % amphibole-dominated fractional crystallization. The geochemical characteristics and genetic type of Heihe granites, associated with coeval sedimentary strata, imply extensional tectonic setting in late Devonian-early Carboniferous. By analyzing the spatiotemporal distribution and geochemical data of the 300–400 Ma magmatic rocks in the Xing'an block, and by conducting locally weighted regression fitting, we propose a geodynamic model. According to this model, the Nenjiang oceanic slab began to rollback at approximately 375 Ma, resulting in the production of the Heihe monzonite and granite. Subsequently, the closure of the Nenjiang Ocean, and collision between the Xing'an block and the Songnen block occurred at around 320 Ma. [ABSTRACT FROM AUTHOR]

Northeast (NE) China underwent complex tectonic processes during the early Mesozoic era, influenced by both the Paleo-Pacific and Mongol-Okhotsk tectonic regimes. However, the dominant factor responsible for the early Jurassic magmatism in the Xing'an block, whether it was the Mongol-Okhotsk or the Paleo-Pacific tectonic regime, remains uncertain. This study aims to investigate the geochemical characteristics, petrogenesis, and geodynamic implications of the early Jurassic A-type granitoids in Heihe, Xing'an block, in order to shed light on the evolution and spatial extent of the Paleo-Pacific tectonic regime. The Heihe A-type granitoids were formed by partial melting of calc-alkaline meta-andesite/basalt under high-temperature and low-pressure conditions. During the later stages of magma evolution, fractional crystallization of K-feldspar played a significant role. The geochemical characteristics of the Heihe A-type granitoids resemble both A 1 -type and intraplate granite, similar to the early Jurassic A-type granites in the Songnen block. The Xing'an block, at least its southeastern margin, was mainly overprinted by the subduction of the Paleo-Pacific oceanic plate during the early Jurassic. This is evidenced by the north-south distribution pattern and the decreasing zirconium saturation temperature from east to west of the early Jurassic igneous rocks in the Xing'an block. The occurrence of early Jurassic various types of A-type granitoids and coeval OIB mafic rocks in NE China could be attributed to the back-arc extension and asthenosphere upwelling triggered by the Paleo-Pacific slab rollback. • The Heihe A-type granitoids were formed by low-pressure melting of juvenile crust. • The Paleo-Pacific tectonic regime was responsible for the Heihe A-type granitoids. • The early Jurassic A-type granitoids in NE China were formed during the slab rollback. [ABSTRACT FROM AUTHOR]

This paper presents U-Pb zircon geochronology, petrology, and major and trace element, Sr-Nd and zircon Hf isotopic geochemistry of Cretaceous granites and intermediate dykes in the Quanzhou and Xiamen regions of southeastern China. These data are used to investigate igneous petrogenesis and Cretaceous tectonic evolution, and interpret the geodynamics of Palaeo-Pacific slab subduction. Granites in Quanzhou and Xiamen range in age from 133 Ma to 87 Ma, have high SiO 2 and K 2 O contents, low abundances in P 2 O 5 , and an A/CNK index that ranges from 0.97 to 1.09, indicating that they are high-K calc-alkaline metaluminous I-type rocks. Slightly negative ɛ Nd (t) values (− 1.2 to − 4.4), young Nd model ages (0.87 Ga to 1.20 Ga) and positive ɛ Hf (t) values (− 0.5 to + 9.9) of zircon grains indicate that the granites were derived from magmas that melted amphibolite in the middle-lower crust, and which may have assimilated country rocks during emplacement in shallow chambers. The intermediate dykes have no genetic link to the granites and magma mixing was negligible. Eight dyke samples have low SiO 2 and high MgO, Ni and Cr contents. Negative ε Nd (t) values (− 1.5 to − 2.7) and positive ε Hf (t) values (2.7 to 7.6) suggest that the dykes were derived from residual basic lower crust after mafic-crystal accumulation. Two samples of adakite-like dykes are characterised by high Sr/Y ratios (89 to 100) and high SiO 2 , low K 2 O, Ni, Cr contents. In combination with slightly negative ε Nd (t) values (− 1.7 to − 1.8) and positive ε Hf (t) values (2.9 to 4.3), the adakite-like dykes were derived from cumulate basic lower crust which had a mixed source between depleted mantle- and crust-derived melts. Based on our data, combined with previously published work, we suggest that extension-induced middle-lower crustal melting and underplating of mantle-derived basaltic melts were the principal driving mechanisms for Cretaceous granitic magmatism in coastal Fujian Province. Extension was related to subduction retreat whereas steep slab subduction caused underplating of mantle-derived basaltic melts. These processes were coupled and mainly responsible for the tectonic transition during the Cretaceous from compression to extension in the coastal belt of the Cathaysia Plate. [ABSTRACT FROM AUTHOR]