中国大陆科学钻探主孔0～4000m岩心的裂变径迹年龄测定

Fission track dating of 0-4000m core samples from main hole of the Chinese Continental Scientific Drilling.

对中国大陆科学钻探(CCSD)主孔0-4000的岩心样进行了裂变径迹年龄测定。在不同深度共测定了38个样品的磷灰石裂变径迹年龄,磷灰石的裂变径迹年龄数据分布在98．6～3．2Ma之间,年龄值的变化规律总体上是随钻孔深度的增加而逐渐减少,地表样的磷灰石裂变径迹年龄是87．1Ma,至3899m深处则为3．2Ma,基于磷灰石中裂变径迹的退火特征,反映出地壳温度随深度的增加而增加的规律。年龄值随深度的变化,也有若干波动,尤其是1550～2450m之间的这部分岩心,在年龄随深度变化的趋势上是不连续的,这部分岩体可以认为是一个重要的构造作用带。根据年龄．深度关系和约束径迹长度的分布特征,对超高压变质岩体的后期折返机制进行了探讨。

A fission track analysis was carried out on the core samples from 0 -4000m in main hole of the Chinese Continental Scientific Drilling （CCSD）. Fission track ages of 38 apatite samples from different depthes were dated. The distribution of them is between 98.6 - 3.2Ma, and the values reduce gradually with depth increasing. The fission track age of surface sample is 87.6Ma, but one$ 3.2Ma on the 3899m depth sample. It shows that the temperature of crust goes up with increasing of depth besed on the characteristic of fission track anealing. The variation of ages, however, has some fluctuation. For example, it is uncontinuous between 1550- 2450m depth. This segment would be a important tectonic belt. Discussing the thermotectonic history and the exhumation machanism of ultrahigh pressure metamorphic rock in later period.