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The Shirenzhang tungsten deposit is a classic wolframite-quartz vein-type deposit located in northern Guangdong Province, eastern segment of the Nanling W-Sn polymetallic belt. The ore veins, controlled by the NW-striking fault system, are mainly hosted in the Ordovician metasedimentary rocks and can also be found with less amount in the cupola of the concealed granitic stock, displaying a typical five-floor vertical zonation proposed by the Chinese geologists. The concealed granitic stock mainly comprises two intrusive facies, the porphyritic biotite granite (G1) in the outer zone and the medium- to fine-grained monzogranite (G2) in the inner zone. In this paper, we report new cassiterite U-Pb ages and Pb isotopes of sulfides for the Shirenzhang tungsten deposit, combined with new zircon U-Pb ages and Hf isotopes, elemental geochemistry and Sr-Nd-Pb isotopes of the concealed granitic rocks, with aims to elucidate the origin of the ore-related granites and the link between the tungsten mineralization and granitic magmatism. LA-ICP-MS zircon U-Pb dating gives the weighted mean ages of 164 ± 2 Ma for G1 and 162 ± 4 Ma for G2, respectively. Cassiterite from the wolframite-bearing quartz vein and the drusy quartz vein yield the weighted mean ages of 164 ± 2 Ma and 160 ± 2 Ma, respectively. These ages suggest that both the granitic intrusion and related W-(Sn) mineralization in the Shirenzhang deposit were initiated during the late Jurassic (ca. 160 Ma). The Shirenzhang granitic rocks are weakly peraluminous highly fractionated I-type granites. Detailed elemental and isotopic data demonstrate that the granitic rocks were derived from partial melting of the Paleoproterozoic basement rocks at a relatively shallow depth of ~30 km triggered by underplating of basaltic magma, and underwent extensive fractional crystallization of hornblende, biotite, feldspar, and monazite and/or allanite. A continental arc setting induced by northwesterly subduction of the paleo-Pacific plate is suggested for the genesis of the Shirenzhang I-type granites. The comparable Pb isotopic compositions of feldspar and sulfides imply that the lead in the ore veins was of magmatic origin. Integrating the spatial-temporal relationship between the ore veins and the concealed granitic rocks with the Pb isotopes from the sulfides and granites, we suggest that the tungsten mineralization is genetically linked with the concealed granitic rocks in the Shirenzhang deposit. Fractional crystallization and melt-fluid interaction may play an important role on the formation of the granite-related tungsten mineralization.

Triassic magmatism in Thailand provides the critical geological record for understanding the evolution of the Paleo-Tethys Ocean. This paper presents zircon U-Pb dating, zircon trace element compositions, elemental geochemistry and Sr-Nd-Hf isotopes for the newly identified Late Triassic granite intrusions in the Upper Peninsula of Thailand where voluminous Late Cretaceous-Paleogene granite intrusions occur. Zircon U-Pb dating results indicate that the two-mica granites were emplaced at ca. 217–216 Ma. The unaltered two-mica granite samples are high silicic (SiO2 = 74.03–75.06 wt%) and display strongly peraluminous characteristics, with A/CNK ratios of 1.21–1.33 and CIPW normative corundum contents of 2.86–3.88 wt%. They have fractionated REE patterns ((La/Yb)N = 5.64–7.34) and notable negative Eu anomalies (Eu/Eu* = 0.35–0.49), with enrichment of Rb, Th, U, Ta and Pb and depletion of Ba, Nb, Sr and Ti. The two-mica granites can be assigned as the highly fractionated S-type granites. They have negative whole-rock eNd(t) (−13.2 to −12.3) and zircon eHf(t) (−11.5 to −7.4) values with corresponding two-stage Nd and Hf model ages ranging from 1.99 to 2.06 Ga and from 1.72 to 1.98 Ga, respectively, indicating a Paleoproterozoic crustal source. The combined geochemical and isotopic data reveal that these rocks were derived by fluid-absent muscovite melting of metapelite at the middle-upper crustal depths and modified by fractional crystallization. In combination of the results in this study with regional geological data, it can be concluded that the two-mica granites were more likely formed during the post-collisional stage of the Sibumasu-Indochina collision, induced by slab break-off of the Paleo-Tethys Ocean. Based on the integrated consideration of a set of factors, including temporal and spatial proximity, source lithology and source enrichment, redox state, and fractional crystallization coupled with melt-fluid interaction, it is suggested that the ca. 216 Ma two-mica granites exhibit high Sn mineralization potential and could be helpful for exploring the primary Sn deposit of Late Triassic age nearby.

Two Early-Middle Triassic magmatic arc belts occur in the Indochina Block within Thailand, namely the Lampang Volcanic Belt and the Loei-Phetchabun Volcanic Belt, which are about 150 km apart and run parallel to each other. The Lampang Volcanic Belt has been extensively studied and suggested to be induced by eastward Paleotethyan subduction, whereas the Loei-Phetchabun Volcanic Belt has not been well constrained due to the scarcity of geochronological and geochemical data. Here we report a detailed study on zircon U–Pb dating, elemental geochemistry and Sr–Nd isotopes for the Phu Rai diorites recently identified in Loei Province, NE Thailand. The Phu Rai diorites yield Middle Triassic (ca. 239 Ma) emplacement ages. They are calc-alkaline rocks characterized by arc-like trace element patterns and depleted Sr–Nd isotopic compositions ((87Sr/86Sr)i = 0.70371–0.70392; eNd(t) = +1.65 to +2.54). These geochemical and isotopic signatures reveal that the Phu Rai diorites were most likely derived from a depleted mantle wedge metasomatized by subducted sediment-derived melts and slab-derived fluids, and modified by limited degree of fractional crystallization involving clinopyroxene, amphibole and Fe–Ti oxides combined with weak plagioclase accumulation. Based on our results and others from the literature, we suggest the existence of an Early-Middle Triassic (ca. 250–239 Ma) magmatic arc belt in NE Thailand, which is not directly linked to eastward Paleotethyan subduction, but is possibly associated with eastward subduction of the Nan back-arc basin. Specifically, the ca. 239 Ma Phu Rai diorites and ca. 245–241 Ma adakites nearby form a rock association in response to slab break-off at that time, immediately after the initial stage of the Sukhothai-Indochina collision. The occurrence of this rock association could mark not only the cessation of eastward subduction of the Nan back-arc basin but also the initiation of the Sukhothai-Indochina collision.

The Late Cretaceous to Paleogene granitoids occur widespread in the Sibumasu block within Myanmar (SE Asia), which show a close association with tin-tungsten mineralization. However, the precise timing, petrogenesis and tectonic significance of these granitoids are poorly constrained so far. In this study, we present a detailed study on geochronology, elemental and Sr-Nd-Hf isotopic geochemistry for the Hermyingyi and Taungphila granites in southern Myanmar, with the aim of determining their petrogenesis and tectonic implications. LA-ICP-MS U–Pb dating of zircon grains from the two granites yield ages of 69–70 Ma, indicating a Late Cretaceous magmatic event. These granitic rocks are weakly peraluminous and belong to the high-K calc-alkaline series. They are both characterized by high SiO2, K2O + Na2O, FeOT/(FeOT + MgO) and Ga/Al ratios and low Al2O3, CaO, MgO, P2O5 and TiO2 contents, enriched in Rb, Th, U and Y, but depleted in Ba, Sr, P, and Eu, suggesting an A-type granite affinity. Moreover, they display prominent tetrad REE patterns and non-CHARAC trace element behavior, which are common in late magmatic differentiates with strong hydrothermal interaction or deuteric alteration. The granites belong to A2-type and probably formed at a high temperature and anhydrous condition. They have zircon eHf(t) values from − 12.4 to − 10.0 and whole-rock eNd(t) values from − 11.3 to − 10.6, with Paleoproterozoic TDM2 ages (1741–1922 Ma) for both Hf and Nd isotopes. Geochemical and isotopic data suggest that these A-type granites were derived from partial melting of the Paleoproterozoic continental crust dominated by metaigneous rocks with tonalitic to granodioritic compositions, without significant input of mantle-derived magma and followed by subsequent fractional crystallization. By integrating all available data for the regional tectonic evolution in SE Asia and adjacent regions, we attribute the formation of the Late Cretaceous A-type granites to a back-arc extension in the hinterland behind the subduction zone, which is induced by the rollback of the flat Neo-Tethyan subducting slab around ca. 70 Ma.

Cretaceous mafic rocks mainly occur along the coast of South China. In comparison, coeval mafic rocks are distributed only sporadically in the inland region, and their petrogenesis and tectonic setting have not been well documented so far. Here we report a detailed study on 40Ar/39Ar dating, elemental geochemistry and Sr-Nd-Pb isotopes for the Yaoling diabases in northern Guangdong, South China. The Yaoling diabases yield a Late Cretaceous (101 ± 1 Ma) 40Ar/39Ar age. These rocks have variable (87Sr/86Sr)i (0.705023–0.709847), relatively uniform eNd(t) (+2.45 to +3.88) and intermediate (206Pb/204Pb)i (18.586–18.692), (207Pb/204Pb)i (15.743–15.764) and (208Pb/204Pb)i (38.300–39.137). These rocks exhibit geochemical affinity to both within-plate and arc magmatism, i.e., relatively high TiO2, Nb and Zr contents, and negative Nb anomalies with (Nb/La)PM of 0.65–0.82. Such dual features indicate that the Yaoling diabases were most likely generated through partial melting of a previously metasomatized lithospheric mantle at a shallow depth (75–85 km), and modified by crystal fractionation. It is likely that the ancient metasomatism may have occurred during the Neoproterozoic oceanic subduction beneath the Cathaysia Block. We suggest that the Yaoling diabases formed in an intraplate extension setting associated with asthenospheric upwelling, possibly in response to the far-field stress that propagated from the paleo-Pacific subduction during the Late Cretaceous (ca. 100 Ma).