华夏地块:一个由古老物质组成的年轻陆块

Cathaysia Block:A Young Continent Composed of Ancient Materials

对华夏地块三个主要前寒武纪地质体出露区变质岩的详细锆石年代学的综合分析显示，华夏地块大致可以被分成武夷山区和南岭-云开区。武夷山区由古元古代核和新元古代（形成于730～820Ma）的盖层组成，构成华夏地块最老的古陆，在其深部很可能还存在一个新太古代基底。新元古代的沉积物主要来自武夷微古陆本身。南岭与云开具有相似的前寒武纪地壳组成，它们主要是由新元古代形成的沉积物夹少量火山岩组成。这些沉积物质中包含了非常古老的中太古代和新太古代组分，甚至古太古代组成。Grenville期和中元古代组分是其中最丰富的。这些组分在华夏没有对应出露的岩石，说明它们主要来自另外一个曾经与华夏相邻的陆块。该陆块很可能是东印度-东南极大陆。南岭-云开区最初可能是Rodinia超大陆裂解时形成的一个裂谷盆地，加里东的造山运动使盆地中的沉积物挤压、褶皱和隆起，与武夷陆块共同构成了一个新的年轻的大陆。

Analyses of detailed U-Pb dating results of zircons from metamorphic rocks in three areas of the Cathaysia block, where Precambrian rocks are exposed, indicate that the Cathaysia block may be subdivided into the Wuyishan and Nanling-Yunkai terrains. The Wuyishan terrain is composed of Paleoproterozoic basement metamorphic rocks and Neoproterozoic （730 -820 Ma） meta-sediments, which is an oldest terrain in Cathaysia block. There may be a Neoarchaean basement at the depth. The Neoproterozoic sediments were from the old Wuyishan mirco-terrain itself. The Nanling and Yunkai regions have similar Precambrian crustal components, which consist of Neoproterozoic sediments and minor interbedded volcanic rocks. These sediments include very ancient Mesoarchaean and Neoarchaean components, sometimes even Paleoarchaean ones. The Grenvillian and Mesoproterozoic materials are most abundant in these sediments. However, these major components have no exposed counterpart rocks found in the Cathaysia block, implying that their provenance was from other continents previously linked with the Cathaysia block. This source continent was likely the eastern India and eastern Antarctica. The Nanling-Yunkai area was originally a rifted sedimentary basin formed during the breakup of Rodinia supercontinent. The Caledonian a new young continent with old orogeny made the sediments in the basin compressed, folded and uplifted, forming Wuyishan micro-continent.