扬子板块北缘新元古代构造属性的岩浆事件制约

黄陵地区新元古代侵入杂岩可为研究扬子板块北缘新元古代构造演化过程及其深部动力学机制提供关键信息。依据岩石组合及分布特征，可将黄陵杂岩划分为黄陵庙岩套、三斗坪岩套、大老岭岩套和晓峰岩套四个单元。本文以黄陵杂岩的围岩崆岭杂岩中花岗片麻岩、黄陵庙黑云母花岗岩和三斗坪闪长岩为研究对象，在系统的野外地质和岩石学研究基础上，开展了LA- ICP- MS锆石U- Pb年代学分析。结果表明，崆岭杂岩花岗片麻岩原岩年龄为1978±13 Ma，且记录了2.5 Ga的构造- 热事件。黄陵庙黑云母花岗岩和三斗坪闪长岩分别形成于815±9 Ma和813±6 Ma，与黄陵庙岩套和三斗坪岩套的侵位时限基本一致。综合分析本次研究结果与前人资料，认为黄陵杂岩主要形成于863~794 Ma，为新元古代早期岩浆活动的产物。通过综述区域地质和地球化学研究资料，认为黄陵杂岩形成于新元古代早期活动大陆边缘的构造环境，提出扬子板块北缘在新元古代早期经历了长期的俯冲- 增生造山过程。

Neoproterozoic tectonic evolution of the northern margin of the Yangtze plate: constraints from magmatic events

The Neoproterozoic intrusive complex in the Huangling area can provide key information for the study of the Neoproterozoic tectonic evolution process and its deep dynamic mechanism in the northern margin of the Yangtze plate. According to the rock assemblage and distribution characteristics, the Huangling complex can be divided into four rock suites as the Huanglingmiao suite, Sandouping suite, Dalaoling suite, and Xiaofeng suite. Based on an integrated study of field geology and petrology, this paper presents new LA- ICP- MS zircon U- Pb geochronological data for the granite gneiss of the Kongling Complex, Huanglingmiao biotite granite, and Sandouping diorite. The results show that the granite gneiss in the Kongling Complex, the surrounding rocks, was formed at 1978±13 Ma, and it also records an earlier tectonic- thermal event at 2.5 Ga. The Huanglingmiao biotite granite and the Sandouping diorite were formed at 815±9 Ma and 813±6 Ma, respectively, which are basically consistent with the emplacement time of the Huanglingmiao and Sandouping suites. These new results, combined with previous published data, suggest that the Huangling complex was mainly formed between 863 Ma and 794 Ma, and was the product of magmatic activity in the early Neoproterozoic. By reviewing regional geological and geochemical research data, it is inferred that the Huangling complex was likely formed in the tectonic setting of an early Neoproterozoic active continental margin. The northern margin of the Yangtze plate might have experienced a long- term subduction- accretionary orogenic process during the early Neoproterozoic.