Chemical and mineral compositions of cherty and siliceous-clayey rocks from accretionary complexes in Sikhote Alin

The paper reports results of a study of clastic heavy mineral assemblages and geochemical features of some assemblages in several Permian-Mesozoic cherty and siliceous-clayey sequences of the Sikhote Alin Region. They are composed of pelagic and hemipelagic sediments of the Panthalassa (Paleopacific) Ocean. Four typical mineral assemblages and their environments are established. In one of the ocean segments, where the sedimentary cover formed during Late Paleozoic - Early Cretaceous, the Permian pelagic domain was characterized by the amphibole-pyroxene assemblage with heavy minerals derived from ophiolites. The Triassic-Jurassic stage was marked by development of the clinopyroxene assemblage with heavy minerals derived from intraplate alkaline volcanic complexes. Middle-Late Jurassic hemipelagic sediments host the zircon-clinopyroxene assemblage with greater role of continental environments and presence of volcanic products of the convergence zone. Another segment of the ocean accumulated red cherts and siliceous-clayey sediments during Jurassic - Early Cretaceous under influence of island-arc volcanism.

本论文报道了锡霍特阿林地区数个二叠纪-中生代燧石质及硅质-黏土岩序列中碎屑重矿物组合与部分组合的地球化学特征研究成果。上述序列均形成于泛大洋（古太平洋）的远洋与半远洋沉积环境。研究确立了四类典型矿物组合及其形成环境：其一，在一个沉积盖层形成于晚古生代-早白垩世的洋段中，二叠纪远洋域以角闪石-辉石组合为特征，其重矿物来源于蛇绿岩；三叠纪-侏罗纪时期则以单斜辉石组合为主，该组合的重矿物来自板内碱性火山杂岩体；中晚侏罗世的半远洋沉积物中赋存锆石-单斜辉石组合，该组合受大陆环境影响更为显著，且伴随汇聚带火山产物的产出。其二，另一洋段在侏罗纪-早白垩世期间受岛弧火山作用影响，沉积了红色燧石及硅质-黏土岩沉积物，对应第四类典型矿物组合。