中国陆相硅藻土物化特征及对硅藻生长、堆埋环境指示意义

Physical and chemical characteristics of diatomaceous earth in China and their environmental indications in growth and burying of diatoms

根据国内硅藻土矿床中硅藻土的硅藻化石组合、物相、化学成份及微量元素特征的分析,对我国地质时期硅藻的生长环境及堆埋条件进行了深入研究,结果表明:1)硅藻生长的水体基本上为陆相淡水湖泊型,其生长所需的硅藻质SiO2主要来源于火山作用;从中新世、上新世到第四纪,硅藻生长的湖盆总体上存在着由浅覆、超覆到退覆沼泽化的演替趋势;同时,气候也相应出现了稳定、动荡至稳定的演化格局.2)硅藻堆积过程中成矿盆地伴随有明显的地壳差异性升降运动,其堆埋的介质条件多为碱性或偏碱性.图4,表3,参23.

A dopting synthetic analyses of diatom group, physical phase assembly, chemical compositions and microelements, the original growth environment and burying condition of diatoms occuring in diatomaceous earth(DE) deposits of China, are studied, which indicates that:1) DE deposits in China almost are lacustrine cause of formation of land facies, water bodies of diatom growth mainly were fresh, few were salt or half salt;2)the differentia of diatom distribution in time is evident, which reflects lake basin of diatom growth totally undergone shallow coverage, overlap and offlap bogginess respectively from Miocene, Piocene to Quaternary, meanwhile, stability, turbulence and stability in climate also appeared, respectively; 3)For burying medium conditions of diatom, alkaline or alkalescence is dominant,and the rising and falling movement of the basin during the burying was remarkable;4)there exists an evident correlativity for SiO2/Al2O3 between volcanic rocks and DEs, which shows that most of clays and diatomaceous silica in DEs came from volcanism. These results are crucial to investicate oreforming conditions, evolutions of climate and lake basin of land facies, and volcanic and tectonic movements since the late Cenozoic.4figs.,3tabs.,23refs.