赣东北地区不同时代硅质岩的地球化学特征及其地质意义

Geochemical Characteristics for Siliceous Rocks of Different Ages in Northeastern Jiangxi and Their Geological Significance

赣东北地区硅质岩各时代均有不同程度的发育 ,各时代硅质岩的SiO2 含量变化范围为74 .90 %～ 97.19% ,Si/Al为 10 .84～ 93.2 1,与Al2 O3呈较好的负相关关系 ,表明它们含有较高比例的陆源泥质沉积物 ,硅质岩样品的Al2 O3/ (Al2 O3+F2 O3) =0 .6 0～ 0 .99,Ce/Ce =0 .99～ 1.2 2 ,(La /Ce) N=0 .91～ 1.83,V/Y <5 .78,Ti/V >17。上述特征表明本区硅质岩形成于大陆边缘构造环境 ,而与大洋盆地及洋中脊构造环境无关。自古生代以来 ,该地区没有出现深海大洋盆地环境。

The siliceous rocks are widely developed in strata of different ages in the northeastern Jiangxi Province. Their SiO_2 contents are in the range of 72.2%～97.19%,and their Si/Al ratios are 10.84～9321. The SiO_2 contents are well negatively correlated with Al_2O_3 contents. This implies that these rocks have a source with higher proportion of terrestrial muddy sediments. Some geochemical characteristics of these siliceous rocks are shown below: Al_2O_3/(Al_2O_3+Fe_2O_3)=0.60～0.99,Ce/Ce *=0.99～1.22, (La / Ce)_N=0.91～1.83; V/Y<5.78,Ti/V>17. These characteristics indicate that they were formed in a tectonic environment of continental margin. There is no relation with the deep oceanic basins and/or mid-ocean ridges. Since the Paleozoic the tectonic environment of deep oceanic basins was not developed in this region.