新疆地质
新疆地質
신강지질
XINJIANG GEOLOGY
2003年
1期
57-64
,共8页
高桥浩%御子柴真澄%高桥裕平%A B Kausa%T Khan
高橋浩%禦子柴真澄%高橋裕平%A B Kausa%T Khan
고교호%어자시진징%고교유평%A B Kausa%T Khan
科希斯坦弧%奇拉斯杂岩体%超镁铁质岩-镁铁质岩组合(UMA)%辉长苏长岩%地球化学
科希斯坦弧%奇拉斯雜巖體%超鎂鐵質巖-鎂鐵質巖組閤(UMA)%輝長囌長巖%地毬化學
과희사탄호%기랍사잡암체%초미철질암-미철질암조합(UMA)%휘장소장암%지구화학
Kohistan .island arc%Chilas complex%ultramafic-mafic association (UMA)%gabbronorite%geochemistry
位于巴基斯坦北部西喜马拉雅的科希斯坦地体为夹持于亚洲板块与印度板块之间的倾斜的岛弧型壳体.科希斯坦岛弧北界为主地幔逆冲断层(MMT),北界为北部缝合带(或喀啦昆仑主逆冲断层,MKT),可将其划分为几个地质单元.奇拉斯(Chilas)杂岩体为一长约300 km、宽50 km的巨型基性侵入岩体,与MMT和MKT近平行展布.它被认为是科希斯坦岛弧的岩浆房根区.奇拉斯杂岩体主要由辉长苏长岩和几个超镁铁质岩-镁铁质岩(简称UMA)岩体组成.前者侵入后者之中.奇拉斯杂岩体岩石普遍发生轻微变形,出现叶理化和韧性剪切带.UMA主要由橄榄石(含或不含单斜辉石)堆积岩(纯橄岩,异剥橄岩)和斜长石-单斜辉石-斜方辉石堆积岩(二辉辉长岩)组成,含有少量单斜辉石-斜方辉石堆积岩(辉石岩).辉长苏长岩的地球化学特征表明其为岛弧环境下形成的非堆积岩,而UMA的地球化学特征表明其为岛弧环境下的堆积岩.辉长苏长岩和UMA的主元素地球化学特征在AFM图解上可用堆积和非堆积的模式来解释.辉长苏长岩的稀土和微量元素地球化学特征在100MgO/(MgO+TFeO)图解上显示岛弧型特点,且UMA表明其堆积特性.
位于巴基斯坦北部西喜馬拉雅的科希斯坦地體為夾持于亞洲闆塊與印度闆塊之間的傾斜的島弧型殼體.科希斯坦島弧北界為主地幔逆遲斷層(MMT),北界為北部縫閤帶(或喀啦昆崙主逆遲斷層,MKT),可將其劃分為幾箇地質單元.奇拉斯(Chilas)雜巖體為一長約300 km、寬50 km的巨型基性侵入巖體,與MMT和MKT近平行展佈.它被認為是科希斯坦島弧的巖漿房根區.奇拉斯雜巖體主要由輝長囌長巖和幾箇超鎂鐵質巖-鎂鐵質巖(簡稱UMA)巖體組成.前者侵入後者之中.奇拉斯雜巖體巖石普遍髮生輕微變形,齣現葉理化和韌性剪切帶.UMA主要由橄欖石(含或不含單斜輝石)堆積巖(純橄巖,異剝橄巖)和斜長石-單斜輝石-斜方輝石堆積巖(二輝輝長巖)組成,含有少量單斜輝石-斜方輝石堆積巖(輝石巖).輝長囌長巖的地毬化學特徵錶明其為島弧環境下形成的非堆積巖,而UMA的地毬化學特徵錶明其為島弧環境下的堆積巖.輝長囌長巖和UMA的主元素地毬化學特徵在AFM圖解上可用堆積和非堆積的模式來解釋.輝長囌長巖的稀土和微量元素地毬化學特徵在100MgO/(MgO+TFeO)圖解上顯示島弧型特點,且UMA錶明其堆積特性.
위우파기사탄북부서희마랍아적과희사탄지체위협지우아주판괴여인도판괴지간적경사적도호형각체.과희사탄도호북계위주지만역충단층(MMT),북계위북부봉합대(혹객랍곤륜주역충단층,MKT),가장기화분위궤개지질단원.기랍사(Chilas)잡암체위일장약300 km、관50 km적거형기성침입암체,여MMT화MKT근평행전포.타피인위시과희사탄도호적암장방근구.기랍사잡암체주요유휘장소장암화궤개초미철질암-미철질암(간칭UMA)암체조성.전자침입후자지중.기랍사잡암체암석보편발생경미변형,출현협이화화인성전절대.UMA주요유감람석(함혹불함단사휘석)퇴적암(순감암,이박감암)화사장석-단사휘석-사방휘석퇴적암(이휘휘장암)조성,함유소량단사휘석-사방휘석퇴적암(휘석암).휘장소장암적지구화학특정표명기위도호배경하형성적비퇴적암,이UMA적지구화학특정표명기위도호배경하적퇴적암.휘장소장암화UMA적주원소지구화학특정재AFM도해상가용퇴적화비퇴적적모식래해석.휘장소장암적희토화미량원소지구화학특정재100MgO/(MgO+TFeO)도해상현시도호형특점,차UMA표명기퇴적특성.
The Kohistan Terrane in the western Himalaya, northern Pakistan, is regarded as a tilted islandarc type crust sandwiched between the Asian and Indian continental crusts. The Kohistan Island Arc isbounded along the south by Main Mantle Thrust (MMT), and along the north by Northern Suture (orMain Karakoram Thrust, MKT), which can be divided into some geological units. The Chilas complex isa huge basic intrusion about 50 km wide and elongates 300 km almost parallel to the MMT and the MKT.It has been interpreted as the magma chamber root zone of the Kohistan Island Arc. The Chilas complexis composed mainly of gabbronorite and several masses of ultramafic-mafic association (UMA). TheUMA is composed mainly of olivine (with or without clinopyroxene) cumulate (dunite, wehlrite) andplagioclase-clinopyroxene-orthopyroxene cumulate (two pyroxene gabbro), with minor amount ofclinopyroxene-orthopyroxene cumulate (pyroxenite). Bulk chemical compositions of major elements forthe gabbronorite plotted on the ternary AFM diagram are suitable to island arc non-cumulate, and thosetor the UMA are suitable to island arc cumulate. Major element geochemistry of the gabbronorite and theUMA, plotted on the variation diagram of 100 MgO/(MgO+TFeO) versus oxides, is explained bycumulate and non-cumulate model.
