北祁连造山带泥盆纪老君山群物源及构造背景分析  

Provenance and Tectonic Setting of Devonian Laojunshan Formation in North Qilian Mountains

作　　者：侯乾[1] 牟传龙[2,3] 王启宇[1,3] 韩梅[1] 谭志远[1] 

机构地区：[1]山东科技大学地质科学与工程学院,山东青岛266590 [2]国土资源部沉积盆地与油气资源重点实验室,四川成都610081 [3]成都地质调查中心成都地质矿产研究所,四川成都610081

出　　处：《山东科技大学学报（自然科学版）》2016年第4期28-36,共9页Journal of Shandong University of Science and Technology(Natural Science)

基　　金：国家重大科技专项"全国油气基础地质编图"(2008ZX05043-005);中国地质调查局项目"中国岩相古地理编图"(1212010916060)

摘　　要：北祁连在泥盆纪经俯冲碰撞造山作用使得古祁连山体整体抬升,并沿造山带北麓及山间盆地形成了巨厚碎屑沉积。本文以北祁连泥盆纪老君山群出露点碎屑岩为研究对象,通过碎屑岩的碎屑组分和地球化学特征分析,探讨其物源区特征和盆地类型。研究认为,北祁连西部剖面砂岩的石英含量4.2%-27.8%,长石含量4.9%-36.2%,岩屑含量非常高,达44.3%-90.3%,砂岩类型主要为岩屑砂岩,岩屑类型以基性-酸性火山岩屑为主,说明西部剖面碎屑岩具有岛弧火山岩特征;东部剖面砂岩的石英含量6.58%-76.12%,长石含量5.32%-24.12%,岩屑含量16.23%-75.45%,岩屑组分为沉积岩岩屑、火山岩岩屑和变质岩岩屑,说明东部碎屑岩的源岩复杂,符合碰撞造山带性质。老君山群碎屑岩化学特征指标为：Al2O3/SiO2值为0.115 2-0.243,K2O/Al2O3值为0.072 5-0.229 4,K2O/Na2O值为0.179-1.8105,LREE/HREE值为2.33-4.92,Eu/Eu＊值为0.46-0.82,各项地化参数分布范围均较广,由物源判别图分析可知,研究区西部物源来自于岛弧,而东部物源来自造山带。因此,由碎屑岩物质组分及其地球化学特征可知,泥盆纪北祁连造山带西部老君山群的盆地类型是与俯冲岛弧相关的弧前盆地,而东部则是与碰撞造山有关的前陆盆地。In Devonian period, North Qilian mountains were suhjected to subduction collision orogeny and the whole ancient Qilian mountain was uplifted. As a result, thick elastic sediments came into being at the northern foot of the orogenic belt and in the intermountain basin. With dew point clastic rock from Laojun formation of Devonian period in North Qilian mountains as the object of study, this paper explored its provenance characteristics and basin types by analyzing the detrital composition and geochemical characteristics of elastic rock. The study shows that with 4.2%-27.8% quartz content, 4.9%-36.2% feldspar content and 44.3-90.3% lithic content, the main type of sandstone in the western section of North Qilian is lithic sandstone and the main lithic is the basic-acid volcanic deb- ris, indicating that the elastic rock from the western section has the characteristics of island arc volcanic rocks. However, with 6.58%-76.12% quartz content, 5.32%-24.12% feldspar content and 16.23%-75.45% lithic con- tent, the lithic from the lithic sandstone in the east of North Qilian are sedimentary lithie, volcanic detritus and met-amorphic lithic, indicating that the complex source rock of the eastern section conforms to the nature of collision o- rogenic belt. The geochemical analyses of the elastic rocks of the Laojunshan formation show that Al2O2/SiO2, K2O/Al2O3, K2O/Na2O, LREE/HREE and Eu/Eu＊ are 0. 115 2-0. 243, 0. 072 5-0. 229 4, 0. 179-1. 810 5, 2.33- 4.92 and 0.46-0.82 respectively and all the geochemical parameters are distributed widely. The analyses of the dis- criminatory plots of provenance indicates that the provenance of the western section comes from island arc while the eastern section comes from orogenic belt. According to the elastic rock material composition and geochemical charac- teristics, the basin type of Laojunshan formation basin in the western section of North Qilian orogenic belt is the fore-arc basin related to the subduction arc while the eastern section is the foreland basin related to the colli

关 键 词：北祁连 老君山群 碎屑组分 地球化学 物源分析 盆地类型 

分 类 号：P588[天文地球—岩石学]