The Mesozoic tectono-magmatic evolution at the Paleo-Pacific subduction zone in West Borneo
The Mesozoic tectono-magmatic evolution at the Paleo-Pacific subduction zone in West Borneo
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DOI：
10.1016/j.gr.2017.05.001
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发表时间：
2017-08
影响因子：
6.1
通讯作者：
J. Hennig;H. Breitfeld;R. Hall;A. M. S. Nugraha
中科院分区：
文献类型：
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作者：
J. Hennig;H. Breitfeld;R. Hall;A. M. S. Nugraha
在西加里曼丹的施万尔山脉西北部有变质和岩浆岩。该地区此前被分配给婆罗洲西南部（SWB），并被解释为澳大利亚起源的区块。主要为白垩纪锆石U-Pb年龄（c. 80-130 Ma），但在西加里曼丹靠近坤甸发现的三叠纪变长岩与SWB成因不一致。由于三叠纪岩石的分布和意义尚不清楚，因此对庞蒂亚克地区的少数暴露点进行了取样，并对其中的两个变火成岩和三个花岗闪长岩进行了地球化学分析和锆石U-Pb年龄测定。三叠纪和侏罗纪的岩浆和变质锆石从变火成岩的解释已经形成在中生代古太平洋边缘，有俯冲下的印度支那-东马来亚块。地球化学相似的岩石三叠纪年龄暴露在Embuoi复杂的北部和Jagoi Granodiastern在西沙捞越建议已形成的部分东南边缘的三叠纪巽他大陆。其中一个花岗岩类（118.6 ± 1.1Ma）具有S型特征，并含有继承的石炭纪、三叠纪和侏罗纪锆石，表明它侵入了巽他大陆基底。早白垩世和晚白垩世两个I型花岗岩和闪长岩的加权平均年龄分别为101.5 ± 0.6和81.1 ± 1.1Ma。这三种岩浆岩都与变火成岩非常接近，并被解释为记录了古太平洋俯冲边缘的白垩纪岩浆活动。变质成因的白垩纪锆石表明在c. 90 Ma可能与Argo地块与Sundaland的碰撞有关。俯冲作用在那时停止，随后在西沙捞越的Pueh（77.2 ± 0.8 Ma）和Gading（79.7 ± 1.0 Ma）侵入体中发生了后碰撞岩浆活动。
Metamorphic and magmatic rocks are present in the northwestern part of the Schwaner Mountains of West Kalimantan. This area was previously assigned to SW Borneo (SWB) and interpreted as an Australian-origin block. Predominantly Cretaceous U-Pb zircon ages (c. 80–130 Ma) have been obtained from metapelites and I-type granitoids in the North Schwaner Zone of the SWB but a Triassic metatonalite discovered in West Kalimantan near Pontianak is inconsistent with a SWB origin. The distribution and significance of Triassic rocks was not known so the few exposures in the Pontianak area were sampled and geochemical analyses and zircon U-Pb ages were obtained from two meta-igneous rocks and three granitoids and diorites. Triassic and Jurassic magmatic and metamorphic zircons obtained from the meta-igneous rocks are interpreted to have formed at the Mesozoic Paleo-Pacific margin where there was subduction beneath the Indochina–East Malaya block. Geochemically similar rocks of Triassic age exposed in the Embuoi Complex to the north and the Jagoi Granodiorite in West Sarawak are suggested to have formed part of the southeastern margin of Triassic Sundaland. One granitoid (118.6 ± 1.1 Ma) has an S-type character and contains inherited Carboniferous, Triassic and Jurassic zircons which indicate that it intruded Sundaland basement. Two I-type granitoids and diorites yielded latest Early and Late Cretaceous weighted mean ages of 101.5 ± 0.6 and 81.1 ± 1.1 Ma. All three magmatic rocks are in close proximity to the meta-igneous rocks and are interpreted to record Cretaceous magmatism at the Paleo-Pacific subduction margin. Cretaceous zircons of metamorphic origin indicate recrystallisation at c. 90 Ma possibly related to the collision of the Argo block with Sundaland. Subduction ceased at that time, followed by post-collisional magmatism in the Pueh (77.2 ± 0.8 Ma) and Gading Intrusions (79.7 ± 1.0 Ma) of West Sarawak.