摘要
分类统计了华北陆块236个精度较高的大于16亿年的年龄数据。统计分析显示,年龄数据存在2个最为明显的峰期,分别位于2550～2475MaBP和1900～1750MaBP区间,对应华北陆块25亿年和18亿年地质事件。同时,这2次地质事件所包含的变质作用峰期和成岩作用峰期均有不同步的特点。25亿年地质事件中成岩作用峰期早于变质作用峰期,而18亿年地质事件中变质作用峰期早于成岩作用峰期。由此反映这2次地质事件性质的差异。25亿年地质事件表现为巨型麻粒岩带、岩浆构造热事件、沉积建造开始和环境变化等,可能代表华北陆块一次重要的拼合事件;而18亿年地质事件表现为非造山岩浆活动、裂谷型火山—岩浆活动和强烈的退变质作用等,可能代表华北陆块一次重要的裂解事件。
We analyzed 236 data of ages older than 1.6 Ga from North China Block (NCB).There are two data peaks which are 2 550 to 2 475 Ma and 1 900 to 1 750 Ma. The two peaks are termed 2.5 and 1.8 Ga geological events respectively. We divided the age data into two groups: diagenesis data and metamorphism data. We find that both groups have two peaks at 2.5Ga and 1.8Ga, but there is difference. For 2.5Ga geological event, major diagenesis took place before major metamorphism. The metamorphism is mostly granulite facies metamorphism. While for 1.8Ga geological event, major metamorphism took place before major diagenesis. The metamorphism is mainly retrograde hornblende facies metamorphism. The rocks formed during this time are mostly magmatic rocks. In this paper, we argue that the characteristics of the metamorphism and the diagenesis apex epochs are related to the property of the geological events and the crustal evolution. During an amalgamation process, the diagenesis may take place before metamorphism. For before and during this process, there are many magmatic events because of heat flow and fluid, but after this process, many rocks may be metamorphosed because of the change of the PT and other conditions. While during an expansion process, the metamorphism may take place before diagenesis. For before and during this process, many rocks may be retrograde metamorphosed and exposed because the changing of P T, and other conditions, while after this process, magmatism takes place to balance the crust. Basing on petrology and chronology, we have a discussion on the property of 2.5 and 1.8 Ga geological events. The characteristics of the 2.5 Ga geological event are:forming of huge granulite belt,happening of magmatictectonicthermal events, beginning of sedimentary formation and changing of environment, and major diagenesis taking place before major metamorphism. It may relate to an amalgamation process in NCB. The characteristics of the 1.8 Ga geological event are: movements of anorogenic magmatism and rift style volcanomagmatic events, strong retrograde metamorphism, and major metamorphism taking place before major diagenesis. It's likely to be represented a rift event in NCB.
出处
《地球科学进展》
CAS
CSCD
2002年第6期818-825,共8页
Advances in Earth Science
基金
国家自然科学基金项目"华北克拉通18亿年重大地质事件:古地幔柱构造与超大陆"(编号:40072061)资助
