摘要
笔者测定了雅鲁藏布江地区蛇绿岩的氦、氩同位素组成。白朗的玄武岩He同位素组成比较均一 ,3 He/ 4He平均值为5 .35 9Ra;与之伴生的变橄岩的3 He/ 4He比值范围为 1.10 4～ 3.384Ra ,平均为 2 .383Ra。从东部的仁布和大竹到西部的下鲁和白朗 ,辉绿岩的3 He/ 4He由低变高。吉定的辉绿岩样品3 He/ 4He比值平均高达 31.5 7Ra,该值与夏威夷发现的高比值样品接近。分步加热法结果显示 ,该样品高比值的He是在低温区段释放的 ,这种高3 He/ 4He比值He的捕获表明雅鲁藏布江蛇绿岩的成因存在地幔柱型富集地幔岩浆作用。
Helium and argon isotopic compositions of Yarlung Zangbo ophiolites in Tibet have been determined in this paper. Helium isotopic compositions of basalts from Bailang are quite uniform with the average 3He/4He ratio being 5.359 Ra,whereas the 3He/4He ratios of meta-peridotites associated with the basalts vary between 1.104 Ra and 3.384 Ra with an average value of 2.383 Ra. 3He/4He ratios in diabases gradually increase from Renbu in the east to Bailang and Xialu in the west. The average 3He/4He ratio of three diabase samples from Jiding is as high as 31.57 Ra, close to the previously reported values from Hawaii hotspots. Further stepwise heating studies reveal that the highest 3He/4He ratio is obtained from the lower temperature intervals. All this suggests that plume magmatism must have played an important role in the formation of the Yarlung Zangbo ophiolites.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2004年第6期621-624,共4页
Acta Geoscientica Sinica
基金
中国博士后科学基金
中国科学院兰州地质研究所气体地球化学国家重点实验室开放基金 (编号 :2 0 0 2 0 3 )资助项目
