Zircon U–Pb and Lu–Hf isotope study of the Neoproterozoic Haizhou Group in the Sulu orogen: Provenance and tectonic implications
Zircon U–Pb and Lu–Hf isotope study of the Neoproterozoic Haizhou Group in the Sulu orogen: Provenance and tectonic implications
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DOI：
10.1016/j.lithos.2011.01.015
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发表时间：
2012-04
期刊：
影响因子：
3.5
通讯作者：
Jian‐Bo Zhou;S. Wilde;Fu-Lai Liu;Jie Han
中科院分区：
文献类型：
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作者：
Jian‐Bo Zhou;S. Wilde;Fu-Lai Liu;Jie Han
新元古代海州群零星出露于中国中东部的苏鲁造山带中。它分为锦屏组和云台组，由石英岩、石英片岩、大理石和含石墨和磷灰石的序列组成。石英片岩的主量和微量元素数据表明，这些岩石有一个杂砂岩原岩，并已沉积在强烈的构造活动。对金平组3个样品和云台组2个样品进行LA-ICPMS U-Pb定年，测得碎屑锆石年龄分别为635~1074Ma和611~943Ma。两组中78%以上的碎屑锆石U-Pb年龄集中在700~890Ma之间，峰值分别为758Ma和828Ma。这表明它们的物源是新元古代岩浆岩，与华南陆块具有构造亲缘关系。一些年龄较大的锆石群体，峰值U-Pb年龄为943和1074Ma。较年轻的人口在661和611 Ma达到峰值。这表明海州群的沉积时代晚于~611Ma，而不是过去认为的中元古代。从同一U-Pb测点采集的锆石Lu-Hf同位素数据显示ε Hf（t）值为负值，为− 22.8~− 7.4，Hf模式年龄为2341~3100Ma。这表明新元古代岩浆岩是古元古代向太古代地壳改造的产物。结果支持海州群与苏鲁造山带西北缘的五莲群相似，都具有SCB亲缘关系的论点，但蓬莱群由于缺乏新元古代时代而不属于SCB。这支持了华北-华南陆块三叠纪缝合带位于沿着百尺河-烟台断裂带的结论，该断裂带位于五莲杂岩的北部和胶北地体的南部，因此五莲-烟台断裂带不是传统意义上的缝合带。
The Neoproterozoic Haizhou Group crops out sporadically in the Sulu orogen in east-central China. It is divided into the Jinping and Yuntai formations and consists of quartzite, quartz schist, marble and graphite- and apatite-bearing sequences. Major and trace element data for quartz schist from the two formations indicate that these rocks have a greywacke protolith and have been deposited during strong tectonic activity. LA-ICPMS U–Pb dating of detrital zircon yields ages of 635 to 1074Ma for three samples from the Jinping Formation and 611 to 943Ma for two samples from the Yuntai Formation. More than 78% of the detrital zircons from the two formations have U–Pb ages grouped between 700 and 890Ma, with two clusters peaking at 758Ma and 828Ma, respectively. This indicates that their provenance is magmatic rocks of Neoproterozoic age that have a tectonic affinity to the South China Block (SCB). A few older zircon populations with peak U–Pb ages at 943 and 1074Ma are also present. A younger population shows peaks at 661 and 611Ma. This suggests that deposition of the Haizhou Group was later than ~611Ma rather than during the Mesoproterozoic as previously thought. Zircon Lu–Hf isotope data collected from the same U–Pb sites show negative εHf(t) values of −22.8 to −7.4 and Hf model ages of 2341 to 3100Ma. This indicates that the Neoproterozoic magmatic rocks were derived from reworking of ancient Paleoproterozoic to Archean crust. The results support the contention that the Haizhou Group is similar to the Wulian Group at the northwestern edge of the Sulu orogen, both having a SCB affinity, but that the Penglai Group does not belong to the SCB because of the absence of Neoproterozoic ages. This lends support to the conclusion that the Triassic suture between the North China and South China blocks is located along the Baichihe–Yantai Fault, which lies north of the Wulian Complex and south of the Jiaobei Terrane; thus the Wulian–Yantai Fault is not the suture zone as is traditionally proposed.