本文選題：滇東南八布　切入點：早二疊世　出處：《地球科學(xué)》2017年01期 　論文類型：期刊論文

【摘要】：滇東南八布基性/超基性巖體被認(rèn)為代表洋殼殘片,與越北Song Hien構(gòu)造帶內(nèi)的蛇綠巖體共同構(gòu)成八布-Song Hien古特提斯縫合帶的重要巖石記錄,是認(rèn)識華南西南緣古特提斯構(gòu)造演化的重要窗口.環(huán)繞八布基性/超基性巖體分布大面積碎屑巖系,內(nèi)夾有硅質(zhì)巖序列,長期以來被認(rèn)為是三疊紀(jì)濁流沉積,但缺少確切的古生物化石和放射性年代學(xué)證據(jù).為確定這套碎屑巖的沉積時代和物質(zhì)來源,對緊鄰八布巖體的龍林西含火山巖屑砂礫巖進(jìn)行LA-ICPMS碎屑鋯石U-Pb同位素和微量元素分析.結(jié)果顯示,碎屑鋯石年齡譜與華南西南緣的二疊系-三疊系年齡譜明顯不同,但與Song Hien構(gòu)造帶晚二疊世砂巖和哀牢山帶綠春二疊紀(jì)砂巖年齡譜相似.最年輕鋯石年齡組約為285Ma,在微量元素組成上與弧/造山型巖漿結(jié)晶鋯石一致,對應(yīng)于安山質(zhì)-流紋質(zhì)火山巖屑,指示早二疊世火山巖漿活動.結(jié)合碎屑鋯石年齡譜的對比分析和八布村東硅質(zhì)巖序列的新發(fā)現(xiàn),結(jié)果表明八布碎屑巖的沉積時代應(yīng)為早二疊世,而非中三疊世,其早二疊世火山巖源區(qū)與八布-Song Hien古特提斯洋俯沖有關(guān).
[Abstract]:The octagonal / ultrabasic rock bodies in southeastern Yunnan are considered to represent oceanic crust fragments, and together with the ophiolite within the Song Hien tectonic belt in the northern part of Yunnan, constitute an important rock record in the paleoTethys suture zone of Babu Song Hien. It is an important window to understand the evolution of PaleoTethys structure in the southwestern margin of South China. A large area of clastic rock series is distributed around the octagonal / ultrabasic rock bodies with siliceous sequences in it, and it has long been considered to be a Triassic turbidite deposit. In order to determine the sedimentary age and material source of this set of clastic rocks, Zircon U-Pb isotopes and trace elements of LA-ICPMS clastic zircon are analyzed in the clastic sand-gravel rocks of Longlinxi, adjacent to the Babu rock body. The results show that the age spectrum of the clastic zircon is obviously different from that of the Permian-Triassic age spectrum in the southwestern margin of South China. But it is similar to the late Permian sandstone age spectrum of the Song Hien tectonic belt and the Luchun Permian sandstone age spectrum of the Ailaoshan belt. The youngest zircon age group is about 285 Ma.The trace element composition is consistent with the arc / orogenic magmatic crystalline zircon. Corresponding to the anshanshanlitic volcanic rocks, they indicate the early Permian volcanic magma activity, combined with the comparative analysis of the age spectrum of clastic zircon and the new discovery of the Babucundong siliceous sequence. The results show that the sedimentary age of the Bubu clastic rocks is the early Permian, not the Middle Triassic. The source of the early Permian volcanic rocks is related to the paleoTethys ocean subduction of Babu Song Hien.
【作者單位】： 中國地質(zhì)大學(xué)生物地質(zhì)與環(huán)境地質(zhì)國家重點實驗室;中國地質(zhì)大學(xué)地球科學(xué)學(xué)院;成都理工大學(xué)沉積地質(zhì)研究院;
【基金】：國家自然科學(xué)基金項目(Nos.41302083,41572078) 中央高校基本科研業(yè)務(wù)費專項資金項目(Nos.CUGL140402,CUG160604)
【分類號】：P588.2;P534.51
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本文編號：1629314