Petrogenesis of late Mesozoic granitoids from the southern segment of the Tan-Lu Fault, eastern China: implications for the tectonic affinity of the Zhangbaling Uplift
Petrogenesis of late Mesozoic granitoids from the southern segment of the Tan-Lu Fault, eastern China: implications for the tectonic affinity of the Zhangbaling Uplift
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中国东部郯庐断裂南段晚中生代花岗岩类的岩石成因：对张八岭隆起构造亲缘关系的意义
DOI：
10.1080/00206814.2020.1716401
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发表时间：
2020
影响因子：
2.6
通讯作者：
Li Zhensheng
中科院分区：
文献类型：
--
作者：
Li Yixi;Yan Jun;Song Chuanzhong;Li Chao;Yang Qingliang;Li Zhensheng
中国东部张八岭隆起（包括北方张八岭地区和肥东南部张八岭地区）晚中生代岩浆岩的研究，可以提供张八岭隆起深部地壳过程和构造亲缘关系的信息。这些岩石以花岗岩类为主，形成年龄为132-120 Ma，最高峰为129 Ma。山口岭脉（120.4 ± 1.1Ma）和朱园掌石英二长岩（129.0 ± 2.2Ma）在肥东地区零星出露。这些岩石具有高Al 2 O3和Sr含量，高Sr/Y、（La/Yb）N和（Dy/Yb）N比值，低Y和YbN含量的埃达克质特征。它们具有富集的（87 Sr/86 Sr）比值，负的εNd（t）和εHf（t）值，非放射成因的Pb同位素组成类似于大别造山带同时代高Sr/Y花岗岩类。这些ZBU岩石可分为两类：一类是Sr-Nd同位素较富集、Mg#值较低（<50）的低镁花岗岩类，另一类是Sr-Nd同位素较弱富集、Mg#值较高（大多>50）的高镁花岗岩类。结合其地球化学特征和前人的实验结果，我们认为低镁花岗岩类是三叠纪陆壳俯冲碰撞导致的原地增厚的下陆壳不含流体的部分熔融产物，而高镁花岗岩类则是岩浆上升过程中与地幔橄榄岩相互作用的脱层榴辉岩下地壳产物。同位素组成表明，这些花岗岩类可能来自扬子地块古地壳，是新太古代和古元古代陆壳重熔的产物。郯庐断裂带深大，使ZBU之下增厚的榴辉岩山根发生拆沉作用，导致高镁岩石的形成和侵位，随后伴随俯冲的古太平洋板块（Izanagi）的回滚，张八岭隆起带发生隆升。
Late Mesozoic magmatic rocks of the Zhangbaling Uplift (ZBU) in eastern China, which comprises the northern Zhangbaling area and the southern Feidong area, can provide insights into the deep crustal processes and tectonic affinity of the massif. These rocks are dominated by granitoids with formation ages of 132–120 Ma and a peak at 129 Ma. The Shankouling dyke (120.4 ± 1.1 Ma) and the Zhuyuanzhang quartz monzodiorite (129.0 ± 2.2 Ma) crop out sporadically in the Feidong area. These rocks show adakitic signatures of high Al2O3and Sr contents, high Sr/Y, (La/Yb)N, and (Dy/Yb)Nratios, and low Y and YbNcontents. They have enriched (87Sr/86Sr)iratios, negative εNd(t) and εHf(t) values, and unradiogenic Pb isotopic compositions that resemble those of coeval high Sr/Y granitoids in the Dabie Orogen. These ZBU rocks can be divided into two groups: low-Mg granitoids with more enriched Sr–Nd isotopic signatures and low Mg# values (<50), and high-Mg granitoids with weakly enriched Sr–Nd isotopic signatures and high Mg# values (mostly >50). Combining their geochemical features with previous results of experimental melts, we conclude that the low-Mg granitoids were derived from fluid-absent partial melting of in situ thickened lower continental crust, resulted from Triassic continental subduction and collision in this area, whereas the high-Mg granitoids were derived from delaminated eclogitic lower crust followed by interaction with mantle peridotites during magma ascent. Isotopic compositions show that these granitoids could have been derived from ancient crust of the Yangtze Block via re-melting of Neoarchean and Paleoproterozoic lower continental crust. The great depth of the Tan–Lu Fault Zone enabled delamination of the thickened eclogitic mountain root beneath the ZBU, which resulted in the formation and emplacement of the high-Mg rocks, followed by uplift of the Zhangbaling massif associated with rollback of the subducting Paleo-Pacific (Izanagi) Plate.