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首页> 外文期刊>International Journal of Earth Sciences >Petrogenesis of late Paleozoic-to-early Mesozoic granitoids and metagabbroic rocks of the Tengchong Block, SW China: implications for the evolution of the eastern Paleo-Tethys
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Petrogenesis of late Paleozoic-to-early Mesozoic granitoids and metagabbroic rocks of the Tengchong Block, SW China: implications for the evolution of the eastern Paleo-Tethys

机译：中国西南腾冲地块的晚古生代至早中生代花岗岩和后生代成岩作用：对东部古特提斯演化的启示

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摘要

This paper presents precise zircon U-Pb, bulk-rock geochemical, and Sr-Nd-Pb isotopic data for metagabbro, quartz diorite, and granite units within the Tengchong Block of SW China, which forms the southeastern extension of the Himalayan orogeny and the southwestern section of the Sanjiang orogenic belt, a key region for furthering our understanding of the evolution of the eastern Paleo-Tethys. These data reveal four groups of zircon U-Pb ages that range from the late Paleozoic to the early Mesozoic, including a 263.6 +/- 3.6 Ma quartz diorite, a 218.5 +/- 5.4 Ma two-mica granite, a 205.7 +/- 3.1 Ma metagabbroic unit, and a 195.5 +/- 2.2 Ma biotite granite. The quartz diorite in this area contains low concentrations of SiO2 (60.71-64.32 wt%), is sodium-rich, and is metaluminous, indicating formation from magmas generated by a mixed source of metamafic rocks with a significant metapelitic sedimentary material within lower arc crust. The two-mica granites contain high concentrations of SiO2 (73.2-74.3 wt%), are strongly peraluminous, and have evolved Sr-Nd-Pb isotopic compositions, all of which are indicative of a crustal source, most probably from the partial melting of felsic pelite and metagreywacke/psammite material. The metagabbros contain low concentrations of SiO2 (50.17-50.96 wt%), are sodium-rich, contain high concentrations of Fe2O3T (9.79-10.06 wt%) and CaO (6.88-7.12 wt%), and are significantly enriched in the Sr (869-894 ppm) and LREE (198.14-464.60 ppm), indicative of derivation from magmas generated by a metasomatized mantle wedge modified by the sedimentary-derived component. The biotite granites are weakly peraluminous and formed from magmas generated by melting of metasedimentary sources dominated by metagreywacke/psammite material. Combining the petrology and geochemistry of these units with the regional geology of the Indosinian orogenic belt provides evidence for two stages of magmatism: an initial stage that generated magmas during partial melting of mantle-derived material associated with late Permian-to-Early Triassic subduction of the Paleo-Tethys, and a second stage that generated granitoid magmas by the partial melting of crustal-derived sources during the Late Triassic collision between the Lhasa and Tengchong blocks and the northern margin of the Australian continent. These rocks, therefore, provide evidence of a systematic late Permian-to-Late Triassic transition from a pre-collision/volcanic arc setting through a collisional setting to a final within-plate phase of magmatism. The previous research involving bulk-rock Sr-Nd analyses of units from the southern Sanjiang orogenic belt and zircon Hf isotopic analyses of units from the Tengchong Block suggests that these areas may record similar magmatic evolutionary trends from mantle- to crustal-derived sources during the evolution of the eastern Paleo-Tethys.
机译：本文介绍了中国西南腾冲地块中的变质岩，石英闪长岩和花岗岩单元的精确锆石U-Pb，块状岩石地球化学和Sr-Nd-Pb同位素数据，这些数据构成了喜马拉雅造山运动的东南延伸和三江造山带西南段，这是进一步加深我们对古特提斯东部演化的了解的重要地区。这些数据揭示了从古生代晚期到中生代早期的四组锆石U-Pb年龄，包括263.6 +/- 3.6 Ma的石英闪长岩，218.5 +/- 5.4 Ma的两云母花岗岩，205.7 +/-的年龄。 3.1 Ma变质单元和195.5 +/- 2.2 Ma黑云母花岗岩。该区域的石英闪长岩含有低浓度的SiO2（60.71-64.32 wt％），富含钠，并且是金属态的，表明岩浆是由混合岩浆岩形成的，这些岩浆岩是由下地壳中混合的变质沉积岩和大量的变质沉积物质组成的。 。两种云母花岗岩含有高浓度的SiO2（73.2-74.3 wt％），高铝质且已演化出Sr-Nd-Pb同位素组成，所有这些都表明地壳来源，最有可能是由于地壳的部分熔融所致。长英质贝利特岩和变质灰泥/硅镁土材料。异辉石含有低浓度的SiO2（50.17-50.96 wt％），富钠，含有高浓度的Fe2O3T（9.79-10.06 wt％）和CaO（6.88-7.12 wt％），并且Sr（ 869-894 ppm）和LREE（198.14-464.60 ppm），表明源自沉积物成分修饰的交化地幔楔产生的岩浆。黑云母花岗岩是弱铝质的，由岩浆形成，岩浆是由变质沉积源（主要由变质灰泥/硅灰石材料）融化产生的。将这些单元的岩石学和地球化学与印支期造山带的区域地质相结合，为岩浆形成的两个阶段提供了证据：初始阶段是在幔源性物质部分熔融的过程中产生岩浆，这与晚二叠纪至早三叠纪俯冲有关。第二阶段，是在拉萨和腾冲地块与澳大利亚大陆北缘之间的三叠纪晚期碰撞中，通过地壳源的部分融化而产生花岗岩岩浆的第二阶段。因此，这些岩石提供了系统的二叠纪晚期至晚三叠世过渡的证据，其从碰撞前/火山弧环境到碰撞环境再到岩浆作用的最终板内阶段。先前的研究涉及对三江南部造山带单元的块岩Sr-Nd分析和腾冲地块单元的锆石Hf同位素分析，表明这些地区可能在记录期间记录了类似的从地幔源到地壳源的岩浆演化趋势。东部古特提斯的演变。

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