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首页> 外文期刊>Journal of Asian earth sciences >Early Paleoproterozoic (ca. 2.36 Ga) post-collisional granitoids in Yunnan, SW China: Implications for linkage between Yangtze and Laurentia in the Columbia supercontinent
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Early Paleoproterozoic (ca. 2.36 Ga) post-collisional granitoids in Yunnan, SW China: Implications for linkage between Yangtze and Laurentia in the Columbia supercontinent

机译：中国西南地区云南的早古生代（约2.36 Ga）碰撞花岗岩体：扬子与劳伦西亚之间的联系对哥伦比亚超大陆的影响

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The early Paleoproterozoic is an essential period for understanding the early tectonic evolution of the Yangtze Block and its reconstruction in the Columbia supercontinent, whereas these issues are largely unknown due to the scarce preservation of early Paleoproterozoic geological records. This study presents rarely reported early Paleoproterozoic granitoids from the southwestern Yangtze Block, with integrated studies of zircon U-Pb ages, Lu-Hf isotopic compositions and whole-rock geochemistry. Magmatic zircon U-Pb dating for two monzogranite samples yields weighted mean Pb-207/Pb-206 ages of 2359 +/- 16 Ma and 2363 +/- 16 Ma, providing unambiguous evidence for the presence of early Paleoproterozoic magmatism in the Yangtze Block. All the samples have high A/CNK values of 1.30-1.61, typical of S-type granite. These rocks have low total REE contents of 72.5-139 ppm with marked enrichment in LREEs ((La/Yb)(N) = 10.73-23.83) and conspicuously negative Eu anomalies (Eu/Eu* = 0.46-0.55). The rocks exhibit uniform primitive mantle-normalized trace element patterns with enrichment in Rb, Th, U and Pb and depletion in Sr, Nb, Hf and Ti. These dated zircon grains have consistent negative epsilon(Hf)(t) values of -6.2 to -2.8 and T-DM2 ages of ca. 2.97-3.16 Ga, indicative of Mesoarchean crustal materials as their magma source. Considering the existence of the ca. 2.36 Ga regional high-grade tectono-metamorphic event, we propose that the ca. 2.36 Ga monzogranites were most likely generated in the early stage of post-collisional extension. Therefore, the southwestern Yangtze Block likely experienced a collision event during ca. 2.40-2.36 Ga, indicative of the involvement of the Yangtze Block in the ca. 2.5-2.3 Ga Arrowsmith orogeny of Laurentia. In addition, a series of accretionary events might also have occurred in the western Yangtze Block before the final assembly of the Columbia supercontinent, implying a tight spatial connection between the Yangtze Block and northwestern Laurentia within this global-scale supercontinent.
机译：早古生代是了解扬子地块的早期构造演化及其在哥伦比亚超大陆的重建的必不可少的时期，而这些问题由于早期古元古代地质记录的稀缺而广为人知。这项研究提出了鲜少报道的扬子西南部古元古代花岗岩，并对锆石的U-Pb年龄，Lu-Hf同位素组成和全岩石地球化学进行了综合研究。对两个辉长岩样品进行岩浆锆石U-Pb测年，得出的Pb-207 / Pb-206加权平均年龄分别为2359 +/- 16 Ma和2363 +/- 16 Ma，为扬子地块中早古元古代岩浆作用的存在提供了明确的证据。 。所有样品均具有1.30-1.61的高A / CNK值，这是S型花岗岩的典型特征。这些岩石的总REE含量较低，为72.5-139 ppm，其中LREE含量显着富集（（La / Yb）（N）= 10.73-23.83），且Eu异常明显为负（Eu / Eu * = 0.46-0.55）。岩石表现出统一的原始地幔归一化痕量元素模式，其中Rb，Th，U和Pb富集，而Sr，Nb，Hf和Ti贫化。这些过时的锆石晶粒具有-6.2至-2.8的一致负ε（Hf）（t）值，且T-DM2年龄约为。 2.97-3.16 Ga，表明其为初中地壳物质。考虑到ca的存在。 2.36 Ga区域的高级构造变质事件，我们提出2.36 Ga monzogranite最有可能在碰撞后伸展的早期产生。因此，西南扬子地块很可能在２００３年经历了一次碰撞事件。 Ga 2.40-2.36 Ga，表明扬子地块参与了该区域。 2.5-2.3劳伦西亚Ga Arrowsmith造山运动。此外，在哥伦比亚超大陆的最后集结之前，扬子西部地区也可能发生了一系列增生事件，这意味着扬子地块与西北劳伦西亚地区之间在全球范围内的紧密联系。

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