共轭伸展褶劈理夹角的定量解析

９０ 年代初以来，中国地质学者先后在浙、皖、赣、湘的“板溪群”及震旦系中发现了古生代的生物化石。因此，再次将“板溪群”是否是前震旦纪的一个变质地层单位、江南古陆是否存在以及华南大地构造格局是否需要重新厘定等问题提了出来。１９９３ 年笔者于赣东北蛇绿混杂岩带内的“双桥山群”岩块中，首次发现了含晚古生代的放射虫硅质岩。１９９６ 年又在该混杂岩带多处的“双桥山群”岩块和“下震旦统志棠组”中找到了含晚古生代的放射虫硅质岩，还首次在“登山群拔竹坑组”中发现了早古生代的几丁虫化石。经数年野外多次观察和对室内化石鉴定、岩石地球化学测试结果以及岩石学特征的综合分析表明，所发现的含晚古生代放射虫硅质岩及其岩石组合是一套洋盆深水相沉积；登山群拔竹坑组，是早古生代的一套浅水陆棚 深水陆棚 半深海相沉积。结合同行学者在邻区“板溪群”研究方面取得的新成果，笔者认为：“板溪群”不是前震旦纪的一个变质地层单位，而是一个复杂的构造岩带，江南古陆是不存在的，华南从早古生代到中生代早期还经历了一次洋盆演化过程，现在的构造格局是印支运动奠定的

Reexamination and impressions on "Banxi Group"

Since the early 90s, Chinese geologists had already discovered the Paleozoic fossils in the “Banxi Group" and Presinian strata in Zhejiang, Anhui, Jiangxi, and Hu'nan Provinces. Therefore, some problems are put forward again, i.e. Whether is the “Banxi Group" a Presinian metamorphous stratigraphic unit? Whether does the Jiangnan Old Land exit? And whether is it necessary to redefine the geotectonic pattern in southern China? In 1993, the authors discovered firstly the late Paleozoic radiolarian silicalite in the “Shuangqiaoshan Group", which, as we know, is a block within the ophiolitic mélange. In 1996, the authors discovered again the late Paleozoic fossils in the other rocks of “Shuangqiaoshan Group" and “Zhitang Formation" of Lower Sinian Series in the ophiolitic mélange. At the same time, the authors discovered firstly the early Paleozoic chitinozoa fossils. Through several years' field observation and through the comprehensive analysis on fossils identification, rock geochemical test result and rock property, it is shown that the late Paleozoic radiolarian silicalite and its rock combination are a suite of oceanic basin abyssal facies deposition, and the Bazukeng Formation of Dengshan Group is a suite of early Paleozoic neritic continental shelf bathyal facies deposition. Combined with the new results gathered by the other geologists in neighbourhood, the authors consider that the “Banxi Group" is not a Presinian metamorphic stratigraphic unit but a complex tectonic belt; the “Jiangnan Old Land" did not exit; from early Paleozoic to early Mesozoic there in southern China experienced an evolutional process of oceanic basin and the geotectonic pattern was established by the Indo China Movement.