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A set of new U–Pb geochronological, elemental and Sr–Nd–Hf isotopic data is presented to constrain the formation age and petrogenesis of granites in SE Thailand, which are significant for understanding eastern Paleotethyan tectonic evolution and regional correlation in SE Asia. Six granite samples from the Chonburi, Rayong–Bang Lamung and Chanthaburi plutons yielded similar crystallization ages of 222–218 Ma. These granites can be geochemically classified into S-type (Group 1) and I-type (Group 2) granites. Both groups have similar chondrite-normalized REE and primitive mantle-normalized multi-element patterns but distinctly different Sr–Nd–Hf isotopic compositions. Group 1 is characterized by more enriched initial 87 Sr/ 86 Sr (i) ratios (0.7101–0.7272) and lower ε Nd (t) values (− 12.0 to − 13.2) compared with those of Group 2 with 87 Sr/ 86 Sr (i) of 0.7027–0.7053 and ε Nd (t) of − 0.6 to − 1.2. Consistently, zircons from Group 1 yield negative ε Hf (t) values of − 7.3 to − 27.4 and Mesoproterozoic or older Hf model ages (T DM = 1.53–2.63 Ga), distinct from those of Group 2 with positive ε Hf (t) values (+ 5.0–+11.3) and younger T DM (0.42–0.67 Ga). Group 1 granites mainly originated from ancient greywackes but Group 2 from juvenile mafic crust with the input of meta-sedimentary component. These data, along with available observations, synthetically indicate that these granites formed in the post-collisional gravitational collapse setting of the thickened crust in response to the assemblage of the Indochina with Sibumasu blocks. They linked northerly and easterly to the Late Triassic granitoids in NW Thailand and East Malay Peninsula related to the Paleotethyan tectonic regime, respectively. [ABSTRACT FROM AUTHOR]

Highlights • Early Paleoproterozoic magmatism were reported in Phan Si Pan Complex in North Vietnam of the Yangtze Block. • The ca. 2.3 Ga quartz monzonite formed at a collision-related crustal thickening event. • The ca. 2.1 Ga A-type gneissic granite formed within an extensional tectonic setting. • The Phan Si Pan Complex was an independent terrane separated from other parts of the Yangtze Block during the early Paleoproterozoic. • The Yangtze Block was linked to northwestern Laurentia in the Pre-Nuna supercontinent. Abstract Our understanding of the early evolution of the Yangtze Block is limited by the sparsely dispersed nature of pre-Neoproterozoic exposures. New, integrated petrographic, zircon U-Pb age and Hf-Nd isotope analyses, and whole-rock geochemical data for early Paleoproterozoic granites in the Phan Si Pan Complex provides new insights into the evolution of the Yangtze Block as well as its role in the Pre-Nuna supercontinent. LA-ICP-MS zircon U-Pb dating of magmatic zircons from quartz monzonite and gneissic granite yielded 207Pb/206Pb ages of 2306 ± 12 Ma and 2096 ± 15 Ma, respectively. Zircons from the quartz monzonite have ε Hf(t) values ranging from −4.1 to −2.1, corresponding to T DM2 model ages of 3002–2890 Ma, whereas zircons in the gneissic granite have ε Hf(t) values between −0.95 and +1.72 and corresponding T DM2 model ages of 2660–2516 Ma, which are consistent with their whole-rock Nd isotope values. Geochemically, the quartz monzonites are I-type granites. Combined with their relatively high Sr/Y ratios and low Y concentrations, as well as fractionated REE patterns with relatively high LREE but low HREE concentrations, they were probably generated by partial melting of the thickened middle-lower crust under elevated temperature. Geochemical and isotopic signatures suggest that the ca. 2.1 Ga gneissic granites are high-K calc-alkaline, ferroan A-type granites formed by partial melting of juvenile crustal source at high temperature and low pressure with little involvement of ancient crustal material. The Phan Si Pan complex has a distinct early Paleoproterozoic crustal evolution history compared with the other crustal provinces of the Yangtze Block, suggesting independent histories that were not unified until the late Paleoproterozoic during the assembly of Nuna. Moreover, the magmatism and tectonic evolution of the north Vietnam region is broadly similar to that of the Arrowsmith Orogen of the Rae craton in Laurentia suggesting a potential spatial linkage. The geologic record of the Yangtze Block does not support an early Paleoproterozoic shutdown of plate tectonics. [ABSTRACT FROM AUTHOR]

New U-Pb geochronological, petrologic, elemental and Sr-Nd-Hf-O isotopic data for the granites from the Inthanon and Sukhothai zones in NW Thailand in conjunction with correlations with SW China are presented to constrain the age and position of the Paleotethys Ocean in this region and the associated assembly of Southeast Asia. The geochronological data show that the granitic rocks in the Inthanon and Sukhothai zones, herein named Group 1 and Group 2 granites, respectively, yield similar crystallization ages of 230–200 Ma. Group 1 samples are characterized by monzogranite and granite with I- and S-type geochemical affinity and Group 2 samples by I-type monzogranite and granodiorite. They have generally similar chondrite-normalized REE and PM-normalized multi-element patterns but distinct Sr-Nd-Hf-O isotopic compositions. Group 1 samples have slightly higher initial 87 Sr/ 86 Sr ratios (0.7111–0.7293) but lower ε Nd (t) values (− 11.1 to − 14.1) than those of Group 2 samples ( 87 Sr/ 86 Sr (i) = 0.7073–0.7278 and ε Nd (t) = − 8.3 to − 11.0). Group 1 samples show the lower ε Hf (t) values (− 5.4 to − 18.2), older T DM (1.62–2.40 Ga) and higher δ 18 O values (+ 7.95 to + 9.94) than those of Group 2 samples (ε Hf (t) of − 11.1 to + 4.80, T DM of 0.96–1.95 Ga and δ 18 O of + 4.95 to + 7.98) for the Triassic crystallization zircons. These geochemical signatures are similar to the Kwangsian and Indosinian granites in the South China and Indochina blocks but distinct from those of the Gangdese I-type granite and Sibumasu Paleozoic granite. Our data suggest that Group 1 samples mainly originated from the early Paleozoic supracrustal rocks containing metapelite and metavolcanic components, which had previously experienced the surface weathering. Group 2 samples were derived from a hybridized source of an old metamorphic and a newly underplated mafic component. Synthesis of our data with available regional observations indicates that the Inthanon zone represents the main suture zone of the eastern Paleotethyan Ocean in NW Thailand and links with the Changning-Menglian suture zone in SW Yunnan (SW China). In NW Thailand, a switch from the eastward subduction of the Paleotethyan oceanic plate to the collision of the Sibumasu with Indochina blocks occurred at ~ 237 Ma, and syn- and post-collisional time being at ~ 237–230 Ma and ~ 200–230 Ma, respectively. The late Triassic granites in the Inthanon and Sukhothai zones are representative of the post-collisional magmatic products. [ABSTRACT FROM AUTHOR]

The consumption of the East Paleotethyan Ocean was the final step in creating the united SE Asia continent. However, uncertainties remain as to the significance of Paleotethyan-associated granitoids and when ocean closure finally occurred in west Indonesia and Malaysia. This paper presents new U-Pb geochronological, petrologic, elemental and Sr-Nd-Pb-Hf isotopic results for granitoids from west Kalimantan, West Java, Bangka-Belitung and Peninsular Malaysia. These granitoids are geochemically subdivided into the Eastern and Main Range granites. The Eastern granites include the granitoids from west Kalimantan, West Java and East Peninsular Malaysia and are dated at ~256–207 Ma, ~208–207 Ma and ~289–217 Ma, respectively. They have ε Nd (t) = +0.2 ~ −9.1, with two-peaks of +0.1 and −5.6, (206Pb/204Pb) i = 18.64–19.49, (207Pb/204Pb) i = 15.61–15.78 and (208Pb/204Pb) i = 38.56–39.47, and originated from a mixed source involving juvenile crust and Indochina basement. The Main Range granites occur in Bangka-Belitung (West Indonesia) and West Peninsular Malaysia, and have crystallization ages of ~226–198 Ma. They share the similar Sr-Nd-Pb-Hf isotopic compositions with those in the South China and Inthanon Triassic granites, with 87Sr/86Sr(t) = 0.70725–0.72652, ε Nd (t) = −5.6 ~ −10.8, ∆8/4 = 28.1–109 and ∆7/4 = 13.7–23.6, and were derived from a meta-greywacke source. Our data reveals the development of the Paleotethyan-associated Permo-Triassic granitoids in West Java, Belitung and west Kalimantan. The Bentong-Raub suture forms the East Paleotethyan suture boundary in Peninsular Malaysia, and extends southwards into the easternmost Bangka-Belitung Islands (and even West Java). To the north, it links to the Inthanon-Changning-Menglian suture in NW Thailand and SW China. It is concluded that the temporal pattern of the East Paleotethyan Ocean in west Indonesia and Malaysia correlates with that in NW Thailand and SW China. Its evolution switched from subduction to assembly of the Indochina-East Malaysia and Sibumasu at ~230 Ma. The Eastern granites might reflect active margin processes in response to the eastward subduction of the Paleotethyan Ocean, and the Main Range granites represent the post-collisional igneous rocks. • The granitoids from West Kalimantan and East Peninsular Malaysia formed at 289–207 Ma. • The granites from Bangka-Belitung and West Peninsular Malaysia formed at 226–198 Ma. • The Bentong-Raub suture southerly extended along the easternmost Bangka-Belitung. • The Permo-Triassic granites in west Indonesia were the Paleotethyan-related products. [ABSTRACT FROM AUTHOR]

• Mesoarchean trondhjemite and potassic granite occur in the Kunming area, southern Yangtze Block. • Trondhjemite formed by partial melting of juvenile mafic crust at low pressure. • Potassic granite formed by partial melting of preexisting TTGs at high pressure. • Yangtze Block is subdivided into northwestern, northeastern and southern domains, which came together in late Paleoproterozoic to form the Yangtze Block. The southern Yangtze is underlain by Mesoarchean igneous rocks that were emplaced in two pulses, including trondhjemites at ca. 3092–3071 Ma followed by potassic granites at 2920 Ma. These represent the oldest TTG suites identified in the southern Yangtze and the oldest potassic granites in the entire Yangtze Block. Hf isotopic analysis reveals ε Hf(t) values of −2.49–7.49 and Hf crustal model ages (T DM C) of 3601–3000 Ma for zircons from the trondhjemites, whereas those from the potassic granites show ε Hf(t) values of −1.79–4.18 and T DM C ages of 3453–3043 Ma. The trondhjemites have high SiO 2 , Mg# and low Al 2 O 3 and K 2 O/Na 2 O, and are highly evolved with low Ni, Cr and Co. The trondhjemites are characterized by low Sr/Y, Eu/Gd and (La/Yb) N , and high Y and HREE, typical of high-HREE and low-pressure TTGs. Their geochemical and isotopic compositions indicate that they are derived from melting of juvenile mafic crust with little contribution from older crustal materials, consistent with a plagioclase-bearing basaltic source. The multielement patterns of potassic granites are similar to that of the trondhjemites, albeit with lower HREE and Y contents. Their high K 2 O values, strongly fractionated REE patterns and low Y contents indicate the presence of garnet and/or amphibole as residual phases in the source region, which indicates they formed at higher pressure than the trondhjemites. The isotopic and geochemical data imply that the formation of the potassic granites could be related to reworking of older TTGs. The increasing K 2 O/Na 2 O of the 3092–3071 Ma trondhjemites to potassic 2920 Ma granites corresponds with stabilization, maturation and thickening of the Archean continental crust in the southern Yangtze. The geochemical data of the TTGs in the Kunming region show important differences from that of contemporaneous TTGs from the Kongling Complex, suggesting that southern Yangtze is composed by an independent old nucleus, which is exotic to the northern Yangtze. A synthesis of petrogenesis, geochronology, geochemistry and isotope data of Archean granites of the Yangtze Block provides important insights into the architecture of its Archean crust. We propose that the Yangtze Block can be subdivided into discrete northwestern, northeastern and southern domains, but which are all affected by late Paleoproterozoic tectonothermal events, suggesting that they had been assembled together by then to form the united Yangtze Block. [ABSTRACT FROM AUTHOR]

• Late Archean and late Paleoproterozoic magmatism occurs in the Phan Si Pan Complex, North Vietnam, of the Yangtze Block. • The 2.85–2.76 Ga potassic granites formed during collision-related crustal thickening. • The ca. 1.86 Ga A-type granite formed within an extensional tectonic setting. • The spatial changes in crustal compositions in the different Archean complexes of the Yangtze Block suggest they constitute separate terranes. • Final cratonization of the Yangtze Block likely relates to the assembly of the Nuna supercontinent. Precambrian igneous and metamorphic rocks of the Phan Si Pan Complex, North Vietnam, constitute the southern extension of the Yangtze Block, and provide a valuable record of the early evolution of the continental crust. We present results of U-Pb zircon geochronology and geochemistry for Precambrian granites in this complex to constrain their emplacement age and genesis. Granites from three plutonic bodies yielded ages of 2848 ± 15 Ma, 2768 ± 19 Ma and 1869 ± 30 Ma, which represent newly-recognized late Archean to Paleoproterozoic potassic granite plutonism in the southern Yangtze Block. The average ε Hf(t) values range from −6.2 to 0.1 for the 2.85 to 2.77 Ga granitic rocks and −13.1 to −9.2 for the ca. 1.86 Ga granitic rocks, with two-stage model ages of 3.64 to 3.20 Ga and 3.31 to 3.07 Ga, respectively, suggesting derivation from partial melting of Paleoarchean and Mesoarchean crust. The late Archean potassic granites exhibit high K 2 O, and high Sr/Y and (La/Yb) N ratios with negligible Eu anomalies, indicating derivation from melting of the thickened lower crust, which is inferred to have occurred in an active margin setting. The late Paleoproterozoic alkali feldspar granites are characterized by high FeO T /(FeO T + MgO)(0.96–0.99) and 10000 * Ga/Al (2.75–2.94) ratios, showing an affinity of A-type granite. These A-type granites exhibit flat chondrite-normalized HREE patterns and strong negative Eu anomalies, and low Sr/Y and (La/Yb) N ratios, corresponding to melting at a shallow depth, probably in a post-collisional extension setting. Comparison of the rock units and events recorded by the Phan Si Pan Complex with other Archean to Paleoproterozoic complexes (Houhe, Dongchuan, Yudongzi, Douling, Zhongxiang and Kongling complexes) in the Yangtze Block indicate spatially distinct histories of crustal growth, and thus may reflect independent terranes. The ca. 1.86 Ga post-collisional magmatism, which succeeds a 2.0–1.9 Ga metamorphic event, is distributed throughout the Yangtze Block, including the Phan Si Pan Complex, suggesting assembly of the disparate terranes and final cratonization of the Yangtze Block overlaps with, and may be related to, assembly of the Nuna supercontinent. [ABSTRACT FROM AUTHOR]