【摘要】：因地層時代和物源區(qū)缺乏有效約束,限制了對龍木錯-雙湖縫合帶東向延伸的北瀾滄江縫合帶北段構(gòu)造演化歷史的認(rèn)識。本文報道了位于北瀾滄江縫合帶北段藏東左貢-竹卡地區(qū)的酉西群、竹卡群和甲丕拉組的鋯石U-Pb年齡數(shù)據(jù),在酉西群變質(zhì)砂巖和甲丕拉組砂巖中獲得的最年輕碎屑鋯石U-Pb年齡加權(quán)平均值分別為410±7Ma(n=3)和215±1Ma(n=2),將二者的最大沉積時代分別限定為早泥盆世和晚三疊世。竹卡群英安巖的鋯石U-Pb年齡(240±1Ma)表明火山巖漿作用發(fā)生于中三疊世。碎屑鋯石年齡頻譜表明,酉西群兼具南羌塘地體約950Ma的碎屑鋯石年齡指標(biāo)和拉薩地體約1110Ma的年齡指標(biāo),表明其初始物源可能來自東岡瓦納大陸內(nèi)部印度大陸與南極洲之間的Eastern Ghats-Rayner和澳大利亞大陸和南極洲之間的Albany-Fraser-Bunger-Windmill造山帶。甲丕拉組碎屑鋯石最年輕的年齡峰值(225±2Ma;n=25)及其Hf同位素組成(-15.7~-4.2)與東達山巖基的相似性,指示甲丕拉組的物源很可能來自鄰近的東達山巖基。甲丕拉組最年輕的碎屑鋯石年齡(215Ma)與東達山巖基最年輕的花崗巖漿活動同期。這一結(jié)果,結(jié)合東達山地區(qū)甲丕拉組與下伏地層之間發(fā)生的與羌塘中央隆起帶同期的區(qū)域性角度不整合事件,提出在北瀾滄江北段的東達山地區(qū),在東達山花崗巖基巖漿作用之后(約215Ma)甲丕拉組磨拉石沉積之前,很可能發(fā)生了快速隆升,與青藏高原羌塘中央隆起帶的隆升剝露事件同期,可能受控于北瀾滄江古特提斯洋殼板片的斷離。
[Abstract]:Due to the lack of effective constraints in stratigraphic epoch and provenance region, the understanding of the tectonic evolution history of the northern section of the northern Lancang River suture belt extending eastward from Longmujia-Shuanghu suture zone is limited. In this paper, the U-Pb age data of zircon from the Zuo Gong Zhuka area in the northern section of the northern Lancang River suture belt are reported, and the zircon age data of the Zhuka Group and the Jiapila formation are reported. The U-Pb weighted mean values of the youngest zircon zircons obtained from metamorphic sandstone and Jiapila formation are 410 鹵7Ma (Nu 3) and 215 鹵1Ma (Nou 2), respectively, which limit their maximum sedimentary ages to early Devonian and late Triassic respectively. The zircon U-Pb age (240 鹵1Ma) of the Zhuka group andesite indicates that the volcanic magmatism occurred in the Middle Triassic. The age spectrum of detrital zircon shows that both the 950Ma age index of the southern Qiangtang terrane and the 1110Ma age index of the Lhasa terrane are both in the group. It is suggested that the initial provenance may come from the Eastern Ghats-Rayner between the Indian continent and Antarctica and the Albany-Fraser-Bunger-Windmill orogenic belt between the Australian continent and Antarctica within the eastern Gondwana continent. The similarity of the youngest age peak (225 鹵2MaN ~ (25) and its Hf isotopic composition (-15.7 ~ (-4.2) to the Dongda base-indicates that the source of the Jiapila formation is probably from the adjacent Dongda mountain base. The youngest clastic zircon age (215Ma) of the Jiapila formation coincides with the activity of the youngest granitic magma in the Dongda massif. This result, combined with the regional unconformity between Jiapila formation and underlying strata in Dongdashan area and the same period in the Qiangtang central uplift belt, suggests that the Dongdashan area in the northern part of the northern Lancang River be located in the northern part of the northern Lancang River. After the magmatism of the Dongdashan granite base (about 215Ma), a rapid uplift occurred before the deposition of the molars of the Jiapila formation, which coincided with the uplift and denudation of the central Qiangtang uplift belt of the Qinghai-Xizang Plateau. It may be controlled by the rupture of the ancient Tethys oceanic crust plate in the northern Lancang River.
【作者單位】： 地質(zhì)過程與礦產(chǎn)資源國家重點實驗室 中國地質(zhì)大學(xué)地球科學(xué)與資源學(xué)院;中國科學(xué)院青藏高原地球科學(xué)卓越研究中心;中國地質(zhì)大學(xué)地質(zhì)過程與礦產(chǎn)資源國家重點實驗室;
【基金】：國家“973”項目(2015CB452604) 國家重點研發(fā)計劃(2016YFC0600304)聯(lián)合資助
【分類號】：P535

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