现代地质
現代地質
현대지질
Geoscience
2015年
4期
789-803
,共15页
屈李华%刘喜方%李金锁%齐路晶
屈李華%劉喜方%李金鎖%齊路晶
굴리화%류희방%리금쇄%제로정
碎屑沉积岩%北羌塘盆地%康鲁组%地球化学%物源%构造背景
碎屑沉積巖%北羌塘盆地%康魯組%地毬化學%物源%構造揹景
쇄설침적암%북강당분지%강로조%지구화학%물원%구조배경
clastic sedimentary rock%North Qiangtang Basin%Kanglu Formation%geochemistry%provenance%tectonic background
沉积盆地中碎屑沉积岩的地球化学特征主要受物源区的制约。对北羌塘盆地三叠系康鲁组碎屑沉积岩进行全岩测试，分析表明，样品的成分变异指数（ICV）和化学蚀变指数（CIA）变化不大，反映其源区物质较新鲜，成熟度相对较低，化学风化作用较弱—中等。岩石SiO2含量普遍较高，TFe2 O3＋MgO含量相对较高，但K2 O／Na2 O比值变化较大。微量元素标准化蛛网图与后太古代页岩和上地壳相似，且REE配分模式图显示富集LREE，δEu明显负异常以及δCe呈弱负异常。此外，Th／U、La／Sc、Th／Sc、Ba／Sr等微量元素比值以及TiO2－Ni、La／Th－Hf、Co／Th－La／Sc和Th／Sc－La／Sc判别图表明沉积物物源具有浅源、长英质的特征。沉积岩的SiO2－K2 O／Na2 O、La－Th、La／Y－Sc／Cr双变量图解和La－Th－Sc、Th－Sc－Zr／10、Th－Co－Zr／10三变量图解，以及Th／U、Rb／Sr等比值特征表明北羌塘三叠系康鲁组沉积砂岩的物源区构造背景以大陆岛弧为主，兼有大洋岛弧和被动大陆边缘构造背景特征。
沉積盆地中碎屑沉積巖的地毬化學特徵主要受物源區的製約。對北羌塘盆地三疊繫康魯組碎屑沉積巖進行全巖測試，分析錶明，樣品的成分變異指數（ICV）和化學蝕變指數（CIA）變化不大，反映其源區物質較新鮮，成熟度相對較低，化學風化作用較弱—中等。巖石SiO2含量普遍較高，TFe2 O3＋MgO含量相對較高，但K2 O／Na2 O比值變化較大。微量元素標準化蛛網圖與後太古代頁巖和上地殼相似，且REE配分模式圖顯示富集LREE，δEu明顯負異常以及δCe呈弱負異常。此外，Th／U、La／Sc、Th／Sc、Ba／Sr等微量元素比值以及TiO2－Ni、La／Th－Hf、Co／Th－La／Sc和Th／Sc－La／Sc判彆圖錶明沉積物物源具有淺源、長英質的特徵。沉積巖的SiO2－K2 O／Na2 O、La－Th、La／Y－Sc／Cr雙變量圖解和La－Th－Sc、Th－Sc－Zr／10、Th－Co－Zr／10三變量圖解，以及Th／U、Rb／Sr等比值特徵錶明北羌塘三疊繫康魯組沉積砂巖的物源區構造揹景以大陸島弧為主，兼有大洋島弧和被動大陸邊緣構造揹景特徵。
침적분지중쇄설침적암적지구화학특정주요수물원구적제약。대북강당분지삼첩계강로조쇄설침적암진행전암측시，분석표명，양품적성분변이지수（ICV）화화학식변지수（CIA）변화불대，반영기원구물질교신선，성숙도상대교저，화학풍화작용교약—중등。암석SiO2함량보편교고，TFe2 O3＋MgO함량상대교고，단K2 O／Na2 O비치변화교대。미량원소표준화주망도여후태고대혈암화상지각상사，차REE배분모식도현시부집LREE，δEu명현부이상이급δCe정약부이상。차외，Th／U、La／Sc、Th／Sc、Ba／Sr등미량원소비치이급TiO2－Ni、La／Th－Hf、Co／Th－La／Sc화Th／Sc－La／Sc판별도표명침적물물원구유천원、장영질적특정。침적암적SiO2－K2 O／Na2 O、La－Th、La／Y－Sc／Cr쌍변량도해화La－Th－Sc、Th－Sc－Zr／10、Th－Co－Zr／10삼변량도해，이급Th／U、Rb／Sr등비치특정표명북강당삼첩계강로조침적사암적물원구구조배경이대륙도호위주，겸유대양도호화피동대륙변연구조배경특정。
The geochemical characteristics of clastic sedimentary rocks in sedimentary basin are mainly con-trolled by the origins of the rocks.In this paper,we report on the whole-rock major and trace element composi-tions of clastic sedimentary rocks in North Qiangtang Basin.The results show that the index of compositional variability and the chemical index of alteration for different samples are similar,revealing a relatively fresh, weakly matured origin with weak-medium chemical weathering.The rocks are characterized by high SiO2 con-tents,and relatively high TFe2 O3 +MgO contents,but K2 O/Na2 O ratios vary largely for different samples.The rocks have the similar trace and REE patterns with the post-Archean Australia shales and upper continental crust,characterized by enrichment in LREE,evident Eu depletions,and weak Ce depletions.Furthermore, the ratios of Th/U,La/Sc,Th/Sc,Ba/Sr of Kanglu Formation and the binary diagrams TiO2 vs.Ni,La/Th vs.Hf,Co/Th vs.La/Sc and Th/Sc vs.La/Sc denote that the origin of the sediments is characterized by superfi-cial and felsic.The tectonic setting discrimination diagrams,such as of SiO2 vs.K2 O/Na2 O,La vs.Th,La/Y vs.Sc/Cr and La vs.Th vs.Sc,Th vs.Sc vs.Zr/10,Th vs.Co vs.Zr/10,and the ratios of Th/U,Rb/Sr sug-gest that the source material of Kanglu Formation in North Qiangtang mainly belongs to continental arc setting, and partially belongs to passive continental margin and oceanic island arc setting.
