扬子陆块~2.0Ga的区域变质事件对南北黄陵古元古代差异演化的启示

~2.0 Ga regional metamorphic event in Yangtze block and its heuristic significance to the geological differences evolutionary between north and south Huangling

扬子陆核黄陵地区发育较为完整的太古宙—古元古代片麻岩、表壳岩组合(即崆岭杂岩),前人调查研究认为南北黄陵Ar-Pt1具有一致的物质组成和地质演化过程。笔者分别对南北黄陵太古宙花岗质片麻岩进行锆石年代学研究发现,北黄陵2件样品(HL013-1、HL013-2)均存在大量锆石发育岩浆核-变质边结构,都获得~2.8 Ga原岩结晶年龄和~2.0 Ga变质年龄;而南黄陵1件样品(HL005-3)以具振荡环带结构的岩浆锆石为主,仅获得~2.9 Ga原岩结晶年龄。结合前人研究成果发现,~2.0 Ga的变质年龄在北黄陵太古宙—古元古代的花岗片麻岩、表壳岩中广泛发育,而在南黄陵相似建造中均未获得,一定程度上说明北黄陵地区广泛遭受~2.0 Ga的区域变质作用而南黄陵不发育,南北黄陵在古元古代可能处在不同地块或者同一地块不同部位。2.1~1.6 Ga的构造岩浆事件的分布特点说明扬子陆块可能存在多条古元古代造山带,扬子陆块古元古代以多块体拼贴为特点,广泛记录2.1~1.6 Ga的构造岩浆事件说明扬子陆块是全球哥伦比亚超大陆的重要组成部分。

A set of integrated Archean-Paleoproterozoic gneisses and supracrustal rocks are exposed in Huangling area, Yangtze continental nucleus, and are named Kongling Complex. Previous research shows that north and south Huangling had the same material composition and geological evolution process in Ar-Pt1. Zircon dating studies of Archean granitic gneiss from the north and the south of Huangling respectively show that two samples(HL013-1 and HL013-2) from the north huangling contain a large amount of zircons with the development of core-rim structure, and have protolith age of ~2.8 Ga and metamorphic age of ~2.0 Ga,whereas one sample(HL005-3) from south Huangling mainly contains magmatic zircons with oscillatory zones, and has a crystallization age of ~2.9 Ga only. Combined with previous research results, the authors found that the metamorphic age of ~2.0 Ga was widely obtained in the Archean-Paleoproterozoic granitic gneiss and supracrustal rocks from north Huangling, but was not obtained in the similar structures from south Huangling. This is probably due to the fact that north Hangling had widely developed^2.0 Ga regional metamorphism but south Huangling had not, and they were probably in different massifs or different parts of the same massif in Paleoproterozoic period. The spatial distribution characteristics of 2.1-1.6 Ga tectono-magmatic events in Yangtze block indicate that there may have existed multiple Paleoproterozoic orogenic belts, characterized by the evolution of multi-block collage in Paleoproterozoic. The extensive records of 2.1-1.6 Ga tectono-magmatic events indicate that the Yangtze block is an important part of the global Columbian supercontinent.