西藏中部伦坡拉盆地古近系沉积有机质特征及意义  

Characteristics and significance of sedimentary organic matter in the Paleogene of Lunpola basin, central Tibet

作　　者：孙涛[1,2] 王成善[1,2] 李亚林[1,2] 魏玉帅[1,2] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质大学青藏高原地质研究中心,北京100083

出　　处：《地球化学》2012年第6期530-537,共8页Geochimica

基　　金：国土资源部国家油气专项(1212011221103);科学技术部中央高校基本科研业务专项资金(2011PY0238);国家自然科学基金(41172129)

摘　　要：西藏中部班公湖-怒江缝合带之上发育一些新生代陆相沉积盆地。与西藏海相沉积盆地相比，这些陆相沉积盆地沉积有机质丰度高、类型好及热演化程度中等，具有很好的油气勘探前景。伦坡拉盆地是其中的代表并且是目前西藏唯一的获得工业油流的盆地。本文对伦坡拉盆地古近系丁青湖组与牛堡组实测剖面有机岩石学及有机地球化学分析研究表明：丁青湖组页岩沉积于半深湖一深湖环境，有机碳含量在284％～692％之间，有机质类型为Ⅰ型和Ⅱ1型，母质主要来源于藻类及少量高等植物的输入，有机质镜质组反射率帜。）在0.46％～0.63％之间，牛堡组泥岩和页岩为滨浅湖相沉积，有机碳含量在0.25％～5.99％之间，有机质类型为Ⅰ型和Ⅱ1型，母质主要来源于藻类及极少量高等植物的输入，镜质组反射率僻。）在0.49％～O66％之间，生物标志化合物组成分布特征显示丁青湖和牛堡组沉积于分层的水体且底部水体盐度较高。A number of continental sedimentary basins, such as Lunpola Basin, Nima Basin, Dongco Basin, and Avengco Basin, were developed during the Cenozoic along the Bangong-Nujiang suture zone, central Tibet. Compared to the marine basins in Tibet, sedimentary organic matter in these basins was characterized by high TOC, good organic matter type and moderate thermal maturity. The Lunpola Basin was a representative of these Cenozoic continental sedimentary basins and it was the only one with commercial oil flows in Tibet. Eleven source rock samples were collected from two cross-sections in the Dingqinghu and Niubao formations of Lunpola Basin for organic petrological and organic geochemical analyses. The results indicated that the shales of Dingqinghu Formation were deposited in a semi-deep to deep lake facies. They contained type I and II1 （oil prone） organic matter, and had TOC contents ranging from 2.84% to 6.92% and vitrinite reflectance data varing between 0.46% and 0.63%. The mudstones and shales of Niubao Formation were deposited in a shore-shallow lake facies, They had TOC ranging from 0.25% to 5.99%, type Ⅰ and Ⅱ1 （oil prone） organic matter, and vitrinite reflectance data varing between 0.49% and 0.66%. In addition, biomarker composition suggested that both Dingqinghu and Niubao formations were deposited in a stratified water column with relatively saline bottom water.

关 键 词：沉积有机质 丁青湖组 牛堡组 生物标志化合物 伦坡拉盆地 西藏 

分 类 号：P593[天文地球—地球化学] P595[天文地球—地质学]