南海深海晚第四纪火山沉积物及其起源探讨

RESEARCH ON VOLCANIC SEDIMENTS AND ORIGIN OF VOLCANIC SUBSTANCE IN SOUTH CHINA SEA DURING LATE QUATERNARY

本文通过对5个岩心和30个表层样品的分析,发现在沉积物中存在着大量的火山物质,有的呈层状,有的则以分散状态存在。电子探针对火山玻璃的测试结果表明,本区的火山物质有两种成分,一种为碱性玄武岩,另一种为岛孤安山岩。从火山灰的形态特征来看,基性火山物质来自海底火山喷发,中性的火山物质来源于陆上的火山喷发。由同位素、碳酸盐含量、孢粉的分析结果推断,317-82-29②岩心是在晚第四纪沉积形成的。此外,^(87)Sr/^(86)Sr的比值表明,南海深海的火山物质起源于上地幔。

The analysis of five piston cores and a large quantity of surficial samples in South China Sea indicates that there is a great number of volcanic ashes in the sediment. Some of them occur as discrete layers and others in a dispersed state. A geochemical analysis of glass shards by electronic microprobe suggests that the volcanogenic substance is basic or neutral. Analysis of experimental data by mathematical method indicates that the basic glass is either picrite or alkaline peridotite in rock composition and that neutral glass is island-arc andesite. According to the morphology of volcanic ash, basaltic shards were formed from phreatmagmatic eruptions and andesite shards from magmatic eruptions.The determination, of uranium series absolute age, calcium carbonate content and spore-pollen analysi of core 317-82-29 ( 2 ) conclude that the sediments in the piston core were formed during the Late Quaternary. According to strontium isotope and chemical characteristics of the volcanic shards, the tephar originated from the upper mantle.