华夏陆块晋宁早期岩浆作用记录及构造背景研究

The amalgamation process of the Yangtze Block to the northwest and Cathaysia Block to the southeast has been paid much attention due to its important significance for the Precambrian tectonic evolution of the South China Block (SCB) and assembly and breakup of the supercontinent Rodinia. In the past decades, the Cathaysia Block has been regarded as an integrated continetal block. However the consideration is not confirmed so far. The probability can not be rejected for the development of the earliest Neoproterozoic arc-back-arc system in the Cathaysia Block. Numerous data show that only the subduction and collision along the Zhangshudong-Shuangxiwu (Jiangshan-Shaoxing suture) occur at early Jinningian period of 970-880 Ma. Available data suggests that the final assembly along the Jiangnan domain and South Anhui did not occur until at least ~830 Ma (late Jinningian) by the Jinningian Orogen, significantly younger than those of the typical Grenville-aged (ca.1.0 Ga) orogenic event associated with the assembly of Rodinia despite that some researchers persisted the amalgamation should be a part of the worldwide Grenvillian orogenic event. The early Jinningian (0.90-1.0 Ga) magmatism and associated orogenesis have been poorly paid attention to in the Cathaysia Block of the SCB at which the strong crustal reworking has been undergone during Phanerozoic period. Based on the geological fingerprinting on the reported literature, this project will document new field, geochronological, geochemical, Sr-Nd-Pb-Os and zircon in-situ Hf-O isotopic data for the mafic-ultramafic rocks, related volcanics and granitic gneiss from the Cathaysia Block. The aim for this project is to (1) evidence the presence and its temporal-spatial pattern for the earliest Neoproterozoic (~0.9-1.0 Ga) magmatism in the Cathaysia Block, (2) recognize a series of earliest Neoproterozoic arc and back-arc systems in the Cathaysia, early Neoproterozoic tectonic pattern across the SCB and its accretionary assembly, and (3) constrain its location to the margin of Rodinia, likely adjacent to West Australia, East Antarctica and India, rather than within the interior of Rodinia.

现有研究普遍将华夏当做一个完整的独立块体，认为其于新元古代沿原江南造山带拼贴于扬子陆块，但现实的问题是华夏陆块中-新元古代究竟是一完整陆块还是发育有弧-盆体系？近十年对原江南造山带的密集研究表明，江南隆起带及皖南伏川一带的岩浆作用年轻于860 Ma, 拼贴发生在~800-830 Ma的晋宁晚期。除在樟树墩-双溪坞地区存在晋宁早期岩浆作用以外，显生宙再造最为强烈的华夏内陆也显示有~0.90-1.0Ga的岩浆作用或造山信息，但当前对这些"蛛丝马迹"极少关注.基于此，本项目拟以现有资料为基础，借助于野外地质、岩石(相)学、岩石/矿物化学、年代学和元素-同位素地球化学为主要手段，寄望多角度确证华夏陆块中-新元古代晋宁早期岩浆作用的存在，获取精细年代学和配套的地球化学数据，厘定其时空分布，阐明华夏陆块中-新元古代的构造格局，为完整理解华南大陆新元古代聚合及其与罗迪尼亚超大陆的关系提供基础资料。

华南前寒武纪最重要的构造事件是新元古代聚合作用，为国内外学者长期关注，近十年的研究已证明，除在赣东北樟树墩-浙东北双溪坞地区存在晋宁早期岩浆作用以外，原江南造山带之江南隆起带及皖南伏川一带的拼贴发生在~800-830 Ma的晋宁晚期。然而华南新元古代现有研究仍聚焦于原江南造山带，对显生宙再造最为强烈的华夏陆块所显示的晋宁早期(~0.90-1.0Ga)岩浆及造山作用信息等“蛛丝马迹”极少关注。基于此，项目以现有“蛛丝马迹”为基础，借助于野外地质、岩石(相)学、岩石/矿物化学、同位素年代学和元素-同位素地球化学为主要研究手段，多角度确证了华夏陆块中-新元古代晋宁早期岩浆作用的存在，获取了精细年代学和系统配套的地球化学数据，确立了华夏陆块晋宁早期岩浆作用的时空分布，构建了华夏陆块中-新元古代弧-盆面貌及其拼贴过程，为华南大陆新元古代聚合及其与罗迪尼亚超大陆关系的完整理解提供突破性资料。