摘要
对浅成热液体系中全岩和单矿物稳定同位素的许多研究表明,虽然在浅成热液体系中大气水占主要成分,但是包括沉积或变沉积成因流体、岩浆水甚至演化了的大气水在内的其它成因流体可能也在浅成热液矿床的形成过程中起一定作用。一般情况下,围岩δ^(18)O值亏损越大,矿床规模就越大。能够形成具有经济意义矿化的全岩δ^(18)O最小的亏损值约为3.5‰。然而,围岩中δ^(18)O的亏损可能会由于低温水合作用对高温蚀变作用的叠加而复杂化,反之亦然。原生的具有低^(18)O值或高^(18)O值的岩浆的存在以及火山气体的蚀变作用也具有同样效果。围岩中δ^(18)O的亏损受流体性质和成分、流体温度、断裂、蚀变发生时岩石的高程、岩性、流体的沸腾效应、蚀变型式以及水/岩比等因素控制。而且,形成浅成热液矿床流体的δ^(18)O值经历了正向漂移。一旦上述的复杂过程和控制因素经过深入研究,氧同位素将成为一种前景广阔的和有力的找矿勘探手段。
Numerous stable isotope studies on whole rocks and mineral separates in epither-mal systems indicate that even though meteoric waters are dominant components in epither-mal systems, fluids of other origins, such as sedimentary or meta-sedimentary fluids, mag-matic waters and even evolved meteoric waters, may also play a role in the formation of ep-ithermal ore deposits. Usually the more depletion in
δ18O in host rocks, the larger the size of ore deposits, and the least depletion degree in whole rocks for economic mineralization is about 3. 5‰. The depletion in δ18O in wall rocks, however, may be complicated by the su-perimposition of low temperature hydration over high temperature alteration or vice versa, the existence of primary low-18O and high-18O magmas, and the alteration by volcanic gases. The depletion in
δ18O in wall rocks is controlled by the composition and nature of fluids, the temperature of fluids, the fractures, the elevation of rocks at the time of alteration, the lithology, the boiling effects of fluids, and the alteration style, as well as the water/rock ratios. In addition, the fluids responsible for epithermal deposits experience positive
δ18O shifts. It seems that when the above complications and controlling factors are well defined, oxygen isotope studies would be a promising and powerful exploration tool.
出处
《地质科技情报》
CAS
CSCD
北大核心
1992年第3期59-66,共8页
Geological Science and Technology Information
关键词
热液矿床
氧
同位素
研究
oxyegn isotope, epithermal system, 818O depletion
