中国浙闽赣地区中生代陆相火山岩同位素年代学

Isotopic geochronology of Mesozoic terrestrial volcanic rocks in the Zhe-jiang-Fujian-Jiangxi area

中国东南沿海特别是浙闽赣地区,中生代以来火山活动频繁、喷发强烈、分布广泛,形成一套陆相火山-沉积地层,同时伴生重要的金属和非金属矿产,成为亚洲西太平洋构造-岩浆-成矿带的重要组成部份。它与北方热河群同属我国研究最早、最详细而时代、岩相又相当的两个代表岩群。由于生物演化的差异、岩性、岩相变化复杂,对这套地层时代的归属、层位划分和对比、火山活动的演化等,各家学者争论了半个多世纪,迄今未能统一。

The Mesnzoic volcanic rocks containing economic mineral deposits are widespread in Zhejiang, Fujian and Jiangxi. Age determination, stratigraphic. classification and evolution oi these volcanic rocks have been the controversial subjects for a long time. The authors have studied systematically and synthetically the sequences of these volcanic rocks on the basis of isotope chronology and isotope geochemistry, and established a series of chronostratigraphic sections of about 130-105 Ma. They are Early Cretaceous in age and not Late Jurassic as usually assumed. The volcanic activities in the east are much younger than those in the west and later than the Rehe Group in North China. The volcanic activities may be divided into four stages: 146-140 Ma, 130-125 Ma, 125-117 Ma and 117-105 Ma, showing a temporal and spatial decrease eastward, and eruption centre migration eastward. Minerali-zntions are closely associated with the four stages of volcanic activities and different types of mineralizations in each stage.