摘要
在中国大陆科学钻探主孔MH-2C取心钻井的第163回次，出现了一处比较短暂的氦气异常，最高值达到17×10^-6（摩尔分数），比基础值高出200％，对应的迟到深度为4906m。气体异常与对应深度的岩心上的X形剪节理相对应。通过对所收集的三个气体样品的氦同位素分析，并对数据进行解析，得到的幔源氦在异常气体中的比例为2．68％-4．58％，说明该岩层中曾有少量幔源流体混入。由于异常持续时间较短，幔源氦比例较低，故推测本次氦异常由裂隙封存的流体所致，该段岩层处于俯冲陆壳的内部而非边缘。
During the core-drilling around 4906m of the CCSD main hole, helium abnormities in the degased phase of the drilling mud were monitored with short duration by the on-site fluid geochemistry laboratory. Three samples were collected with the maximum He concentration of 17 × 10^-6, which was about two times higher than the normal values. The samples were typically mixtures of dissolved air and formation fluid. Based on the monitored helium content and its corresponding isotopic data in the samples, helium origins were reconstructed with contributions of 2.68% -4.58% from mantle. The existences of mantle helium suggest that mantle fluid intrusion into the formation through cracks or faults during crust subduction-retraction process. The short duration of helium abnormity and relatively low ratio of mantle helium may imply that the abnormity was caused by release of crack-sealed fluids.
出处
《岩矿测试》
CAS
CSCD
2006年第1期1-4,共4页
Rock and Mineral Analysis
基金
国家重点基础研究发展规划项目(2003CB716508)
国家自然科学基金重大项目(40399144)
国家九五重大科学工程项目"中国大陆科学钻探工程"
