同位素示踪技术在地质研究中的某些应用

SOME APLLICATIONS OF ISOTOPE TRACING IN GEOLOGY

文中介绍了同位素示踪技术的基本原理，回顾了利用氢氧同位素示踪成矿溶液来源，研究水岩反应所取得的重要成果和最新进展；提出水岩相互作用是一个连续的演化过程，可分三个阶段，不同阶段的交换温度、水／岩比及体系的平衡、封闭情况是不一样的。以太古宙条带状硅铁建造为例，介绍了硅同位素示踪技术的新进展，证明了太古宙条带状硅铁建造为海底喷气成因，条带状构造与海底热液的周期性喷发有关。文中还介绍了氦同位素在示踪幔源组份方面的最新进展，指出我国东部油气区天然气中的氦、氩、二氧化碳等有相当一部分来自地幔；根据太平洋中部多金属结核的氦同位素组成和分布特征，提出成矿物质主要来源于海底热液活动，结核的一个圈层可能代表了一次大的海底热液活动。

The theory of isotope tracing and some new progresses of studies on isotopes such as hydrogen, oxygen, silicon and helium are introduced in this paper. Oxygen isotope exchange between water and rock, which is a continuous evolution process, may be divided into three steps. The temperature of interaction, W/R and condition of the system are different in every step. During the oxygen isotope exchange between meteoric water and rock, the δ 18 O values of rock may be decreased in some conditions, while, it can also be increased in some other ones. According to the characteristics of silicon isotope in Gongchangling, Liaoning province, the evidence shows that the Archean banded iron formation (BIF) is related to the sea floor exhalative sedimentation and also that the banded structure is attributed to the periodic exhalation. The abundance of helium, argon and carbon dioxide, and their values of 3He/ 4He, 40 Ar/ 36 Ar and δ 13 C CO 2 in the oil gas fields in East China are very high, which suggest that most of them come from mantle. 3He/ 4He ratios of submarine polymetallic nodules from the East Pacific Basin (C C zone) are large (10 -5 ～10 -4 ). 3He/ 4He ratios in the inner layers of nodules are more higher than those in the outer layers. Besides, the distribution of these ratios shows a regional regularity. All of these suggest that the formation of nodules was associated with submarine hydrothermalism; and each layer of the nodules may represent one stage of intense submarine hydrothermalism.