Southeast Asia plays a key role in the evolution of the eastern Tethys, which is characterized by accretion and amalgamation of numerous terranes since early Paleozoic. In the present study, an early Paleozoic granitoid sequence from the Kontum massif in the central Indochina block was investigated to reveal the early Paleozoic accretionary orogenesis of the eastern Tethys. Early Paleozoic Kontum granitoids include diorites and granites. Early Ordovician (485–473 Ma) Ben Giang diorites show high Mg#, Cr and Ni contents, and negative Nb-Ta and positive Pb anomalies as well as positive zircon ɛ_Hf(t) values (+6.2 to +10), probably reflecting the melting of a metasomatized mantle wedge. Late Ordovician (457–453 Ma) Dien Binh hornblende-bearing diorites and granites exhibit low Mg#, Cr and Ni contents, and negative Nb-Ta and positive Pb anomalies as well as negative zircon ɛ_Hf(t) values (−8.7 to −4.2), which is interpreted to reflect the reworking of ancient continental mafic crust during subduction. In contrast, the Silurian (422 Ma) Dai Loc muscovite-bearing granites are characterized by relatively high A/CNK and heavy rare earth element contents, and a negative Eu anomaly, corresponding to a typical S-type granite affinity. Their negative zircon ɛ_Hf(t) values (−6.0 to +0.6) suggest that a petrogenesis linked to reworking of crustal sediments. In combination with the widespread occurrence of coeval high-pressure metamorphism, we suggest that an advancing accretionary orogenesis was responsible for the generation of the early Paleozoic magmatic arc in the Kontum massif. Such magmatic arc systems dominated the early Paleozoic evolution of the northern Gondwana margin during the subduction of the Proto-Tethys.

中文翻译：

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东南亚印度支那地块的早期古生代弧岩浆作用和增生造山作用

东南亚在特提斯东部的演变中起着关键作用，其特征是自古生代以来大量地体的积聚和融合。在本研究中，对印度支那中部地块的Kontum断层的古生代早期花岗岩序列进行了研究，以揭示特提斯东部的早古生代增生造山作用。早古生代的Kontum花岗岩类包括闪长岩和花岗岩。早奥陶纪（485-473 Ma）本江红闪长岩显示出高的Mg＃，Cr和Ni含量，负Nb-Ta和正Pb异常以及正锆石ɛHf _（t）值（+6.2至+10），可能反映了交代化的地幔楔的融化。晚奥陶纪（457–453 Ma）含Dien Binh角闪石的闪长岩和花岗岩显示出低Mg＃，Cr和Ni含量，负Nb-Ta和正Pb异常以及负锆石ɛHf _（t）值（-8.7至-4.2），这被解释为反映了俯冲过程中古代大陆性镁铁质壳的再造。相比之下，志留纪（422 Ma）大禄白云母花岗岩的特征是相对较高的A / CNK和重稀土元素含量，负Eu异常，对应于典型的S型花岗岩亲和力。负锆石ɛHf _（t）值（-6.0至+0.6）表明成岩作用与地壳沉积物的返修有关。结合广泛存在的近代高压变质作用，我们认为前进的增生造山作用是造成Kontum断层中早古生代岩浆弧形成的原因。在原始特提斯俯冲期间，这种岩浆弧系统主导了冈瓦纳北部边缘的早期古生代演化。