南海东部重矿物分布特征及其影响因素

The Distribution Characteristics of Heavy Minerals in the East of South China Sea and Their Controlling Factors

对南海东部 1 88个站位表层沉积物样品 63～ 1 2 5μm粒级重矿物的研究表明 ,重矿物种类有50种 ,最高含量可达 1 2 .82 % ;平均含量较低 ,为 1 .1 1 % ,;矿物组成以普通角闪石、铁锰微结核、磁铁矿、普通辉石为主。重矿物来源复杂多样 ,包括陆源、火山、自生等各种来源的矿物。陆源重矿物多分布在水深 3 50 0 m以浅的北部陆坡 ,主要来源于台湾海峡和台湾岛 ;此外还有经巴士海峡由洋流带入的吕宋岛等的剥蚀物 ,珠江物质对研究区的影响较小。自生沉积矿物主要分布于 1 6°N～ 2 0°N之间的下陆坡区和深海平原 ,其中铁锰微结核富集于沉积速率较低的氧化环境 ,自生黄铁矿则富集于局部还原环境或生物壳室中。火山碎屑矿物主要分布于 1 5°N两侧的深海平原和海山区 ,来源于海底火山岩的剥蚀物和附近弧状列岛的火山喷发物。沉积环境是影响重矿物分布的主要因素。

Heavy minerals from the very fine sand fraction(63～125μm) in surface sediments have been identified and analyzed from 188 stations in the east of South China Sea. The results reveal fifty mineral species occur in surface sediments from the easte of South China Sea. The contents of heavy mineral are low, and it is only 1.11%, and the maximum is 12.82%. The minerals mainly consist of hornblende, ferromanganese micronodule, magnetite and augite. The provenances of heavy minerals are different, including the terrigenous mineral, authigenic mineral and volcanogenic mineral, etc. The terrigenous minerals mainly distribute in the north continental slope with the water depth less than 3 500 meters, and are mainly at the Taiwan Strait and Taiwan island. In addition eroded materials from the Luzon Island, carried by current are brought into the east of South China Sea through the Bashi Strait. Materials from the Pearl River have little effect in the east of South China Sea. The authigenic minerals mainly distribute in the lower continental slope and abyssal plain between the latitude of 16°N～20°N. Ferromanganese micronodules enrich in the oxidizing environment with lower sedimentation rate. While authigenic pyrites occur in the reducing microenvironment or in the shells. The volcanogenic minerals mainly distribute in the abyssal plain and the seamount near the latitude of 15°N, mainly come from the erosion of the volcanic rocks in the seabed and the volcano eruptions in the vicinity of islands. The sedimentary environment is the main factor that controls the distributions of heavy minerals.=