藏东左贡-竹卡地区一些关键地层的时代和物源区示踪
发布时间：2018-08-26 16:41
【摘要】：因地层时代和物源区缺乏有效约束,限制了对龙木错-双湖缝合带东向延伸的北澜沧江缝合带北段构造演化历史的认识。本文报道了位于北澜沧江缝合带北段藏东左贡-竹卡地区的酉西群、竹卡群和甲丕拉组的锆石U-Pb年龄数据,在酉西群变质砂岩和甲丕拉组砂岩中获得的最年轻碎屑锆石U-Pb年龄加权平均值分别为410±7Ma(n=3)和215±1Ma(n=2),将二者的最大沉积时代分别限定为早泥盆世和晚三叠世。竹卡群英安岩的锆石U-Pb年龄(240±1Ma)表明火山岩浆作用发生于中三叠世。碎屑锆石年龄频谱表明,酉西群兼具南羌塘地体约950Ma的碎屑锆石年龄指标和拉萨地体约1110Ma的年龄指标,表明其初始物源可能来自东冈瓦纳大陆内部印度大陆与南极洲之间的Eastern Ghats-Rayner和澳大利亚大陆和南极洲之间的Albany-Fraser-Bunger-Windmill造山带。甲丕拉组碎屑锆石最年轻的年龄峰值(225±2Ma;n=25)及其Hf同位素组成(-15.7~-4.2)与东达山岩基的相似性,指示甲丕拉组的物源很可能来自邻近的东达山岩基。甲丕拉组最年轻的碎屑锆石年龄(215Ma)与东达山岩基最年轻的花岗岩浆活动同期。这一结果,结合东达山地区甲丕拉组与下伏地层之间发生的与羌塘中央隆起带同期的区域性角度不整合事件,提出在北澜沧江北段的东达山地区,在东达山花岗岩基岩浆作用之后(约215Ma)甲丕拉组磨拉石沉积之前,很可能发生了快速隆升,与青藏高原羌塘中央隆起带的隆升剥露事件同期,可能受控于北澜沧江古特提斯洋壳板片的断离。
[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 卤7Ma (Nu 3) and 215 卤1Ma (Nou 2), respectively, which limit their maximum sedimentary ages to early Devonian and late Triassic respectively. The zircon U-Pb age (240 卤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 卤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.
【作者单位】： 地质过程与矿产资源国家重点实验室 中国地质大学地球科学与资源学院;中国科学院青藏高原地球科学卓越研究中心;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：国家“973”项目(2015CB452604) 国家重点研发计划(2016YFC0600304)联合资助
【分类号】：P535
本文编号：2205519
[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 卤7Ma (Nu 3) and 215 卤1Ma (Nou 2), respectively, which limit their maximum sedimentary ages to early Devonian and late Triassic respectively. The zircon U-Pb age (240 卤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 卤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.
【作者单位】： 地质过程与矿产资源国家重点实验室 中国地质大学地球科学与资源学院;中国科学院青藏高原地球科学卓越研究中心;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：国家“973”项目(2015CB452604) 国家重点研发计划(2016YFC0600304)联合资助
【分类号】：P535
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