冲绳海槽岩浆性质的变化特点:斜方辉石提供的信息  

CHARACTERISTIC VARIATIONS OF MAGMA IN THE OKINAWA TROUGH: INFORMATION DERIVED FROM THE ORTHOPYROXENE

作　　者：曾志刚[1] 付永涛[1] 陈丽蓉[1] 

机构地区：[1]中国科学院海洋研究所,青岛266071

出　　处：《海洋与湖沼》2006年第1期84-89,共6页Oceanologia Et Limnologia Sinica

基　　金：中国科学院知识创新工程重要方向项目;KZCX3-SW-223号;国家重点基础研究发展规划项目;G2000046701号;国家自然科学基金项目;40376020号和40176020号;国家大洋重大专项课题资助;DY105-01-03-1号。

摘　　要：对冲绳海槽18个表层样品和11个柱状样品的156个层次中的火山成因斜方辉石进行了电子探针分析,计算了斜方辉石的FS值。结果表明,其FS值具有南高北低的特点,反映出在冲绳海槽从北向南岩浆性质由基性向酸性的变化。各沉积物岩芯中,斜方辉石的FS值自下而上的变化,则反映出冲绳海槽的岩浆性质从早期到晚期,具有由酸性向基性、由基性向酸性、稳定型和波动型四种变化形式。Okinawa Trough is a young back-arc basin. Studying the volcanic rocks in Okinawa Trough is one of the key points to understand the evolution of chinese marginal sea. Recently due to the limit of sampling condition,however,we can not have a integrated and general knowledge of the distribution of volcanic rocks in Okinawa Trough, which distinctly influences our discussion,based on Okinawa Trough, on the inner relationship of Ryukyu trench,Ryukyu island-arc and Okinawa Trough during their evolution, meanwhile we can also not further our understanding about the inner relationship between Okinawa Trough magmatism and submarine hydrothermal activity. In order to resolve these problems,we can supplement our cognition on the basic characteristic of volcanic activity in Okinawa Trough by realizing the information of volcanic recorded in the sediment core,for example by the research of volcanic ashes, volcanic glass and volcanic mineral. Guided by this idea, in this paper we utilize the Fs value of orthopyroxene （ferroaugite tool percent） to discuss the variation characteristics of magma from northern to southern Okinawa Trough. There are large amount of volcanogenic pyroxene in volcaniclastic sediment in Okinawa Trough. They are sandy beige-snuff color and kelly-green-bottle green. They are columnar automorphie crystals. The largest ratio of macroaxis/bractlyaxis is 4： 1. Some of the crystals have glazed surface, intact crystal face and crystal edge, and some of have been seriously eroded, which results in the misproportion and rough surfaces of these crystals. Some of crystals are covered by volcanic glass and the grain diameter is 0. 5-0. 25mm. In addition most of the pyroxenes have magnetite inclusions which have perfect oetahedron and half expose outside of the pyroxene, Shi Jianyou studied the chemical composition of above pyroxenes by the electron microprobe. The research of the chemical composition for 203 pyroxene samples demonstrated that the pyroxene is mainly composed of the orthopyroxene, and less t

关 键 词：斜方辉石 岩浆性质的变化特点 冲绳海槽 

分 类 号：P736.15[天文地球—海洋地质]