摘要
该区的碎屑矿物有以下三个来源:即陆源碎屑物质;海底火山喷发的产物及少量海底自生矿物。其中火山喷发的碎屑矿物晶形完好,常包裹着一薄层火山玻璃,这些矿物以紫苏辉石为主,其次是普通辉石、角闪石、磁铁矿、磷灰石等。此外,还有许多浮岩碎块及火山玻璃碎屑,在浮岩的碎块中含有斜长石(An=30—80)、紫苏辉石、磁铁矿及少量橄榄石的斑晶。根据碎屑矿物的组合特征将该区分为3个矿物区和3个矿物亚区。
Samples of marine sediments,including some fragments of pumice and other volcanic rocks,have been collected from Okinawa Trough since 1978.Forty-three bottom surface sediment samples were analysed.Their heavy and light mineral contents,as well as their distribution patterns were studied.According to their mineralogical characteristies and their provincial difference in sources,the studied mineral assemblages can be divided as follows:1.Volcanic type These minerals usually occur as euhedral crystals with complete dome,frequently covered with volcanic glasseas.They are found only in the eastern and northern part of Okinawa Trough.In this type hypersthene is the predominant component,while augite,magnetite,vol-canic glass,quartz and feldspar rank the second in abundance,and hornblende is the third.In additon,a lot of fragments of pumice,andesite and basalt were dredged from Okinawa Trough.The fragments of pumice include constantly phenocrysts of hypersthene,plagioclase and oliven.The plagioclase phenocrysts phenocrysts are referred to as and esine and labradorite(An=30—80%).2.The continental shelf type These minerals occur in anhedral crystals without dome.They were mostly broken and rounded.This type occur only in the western slope and southern part of Okinawa Trough.In this type,quartz,feldspar,hornblende,platy minerals and epidote are the predominant components.Garnet and titanite are less.3 The authigenic type These minerals are composed of pyrite,glauconite,collophanite and others,of which the dominant component is pyrite.Discussion The Okinawa Trough may be divided into three provinces and three subprovinces according to their heavy and light mineral assemblages.1.The eastern slope mineral province.These sediments came from the submarine volcanic products and the volcanic rocks of the Ryukyu Islands.2.The northern part mineral province.The sediments of this province are chiefly composed of fragments of submarine volcanic products.3.The Western slope and southern part mineral province.In this mineral province three mineral subprovinces can be distinguished by the different contents of platy minerals and dolomite.a.The northern-western slope mineral subprovince.b.The southern-western slope mineral subprovince.c.The southern part of Okinawa Trough mineral subprovince.The principal sediments of the mineral subprovinces a and b came from the continental shelf of the East China Sea.But the turbidity sediments were mainly deposited in subprovince c.The mineral components of these turbidites were also from the continental shelf of the East China Sea.Based on the research of the volcanic minerals and rock fragments,it is suggested that the property of the proto magma in the Ckinawa Trough should be referred to neutral basic magma.
作者
陈丽蓉
徐文强
申顺喜
李安春
Chen Lirong;Xu Wenqiang;Shen Shunxi;Li Anchun(Institute of Oceanology,Academia Sinica,Qingdao)
出处
《海洋与湖沼》
1986年第1期3-12,93,共11页
Oceanologia Et Limnologia Sinica
