摘要
位于松潘—甘孜带东北部的若尔盖盆地是中、晚三叠世时期松潘—甘孜构造带北部重要的沉积区。对若尔盖地区的红参一井内中三叠世中期和晚三叠世中期的37个杂砂岩样品进行了ICP-MS微量元素分析,其结果显示这些砂岩样品具有Cs、Rb、Th等元素富集,Sr、Nb和Ta亏损,稀土元素总量较高,且负Eu异常和轻重稀土分异明显等壳源物质的特征;而微量不活动元素的含量及比值特征以及构造环境判别图解的判别结果表明:若尔盖盆地中三叠世中期到晚三叠世中期的沉积构造环境为大陆岛弧,沉积物源受到大陆岛弧的强烈影响。通过对比杂砂岩稀土元素组成在上层和下层样品之间的变化,若尔盖盆地内中三叠世中期到晚三叠世中期及晚期沉积物源区的构造背景和性质发生了明显的改变,而这一变化很可能是盆地东侧成熟陆壳在晚三叠世后期被抬升和剥蚀,其大量碎屑物质被带到盆地的结果。
Situated in Northeast tary area of this terrain from Middle of Songpan- Ganzi terrain, the Zoige Basin is a significant sedimento Late Triassic. 37 greywacke samples of Middle and Late Triassic collected from Hongcan well in Zoige were analyzed by ICP - MS for REE and trace elements. The result shows that these samples were originated continental crust because they enriched in Cs,Rh,Th and high REE contents and depleted in Sr,Nh and Ta. Negative Eu anomalies and strong differentiation between heavy and light REE are significant. Both the contents and ratios of the inactive trace elements and the results based on discriminant diagrams indicated that the sedimentary tectonic setting of Zoige Basin was dominated by continental island arc and the sediment in this basin was strongly affected by continental island arc between Middle and Late Triassic. The change of REE composition between the upper and lower samples from Hongcan well implied the tectonic setting and property of the sediment provenance in Zoige Basin were altered obviously between late-period of Middle Triassic and mid-period or late-period of Late Triassic. This change was probably due to elevation and erosion of the matured continental crust on the east of Zoige Basin, and lots of clastic materials transported into the basin in late-period of Late Triassic.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2008年第2期240-248,共9页
Journal of Jilin University：Earth Science Edition
基金
中石化南方勘探公司项目(04016141)
关键词
杂砂岩
沉积物源
构造环境
大陆岛弧
若尔盖盆地
greywacke
sediment provenance
tectonic setting
continental island arc
Zoige Basin
