辽东－吉南地区早元古代硼镁石型硼矿床地质特征及矿床成因

通过对辽东－吉南硼矿床地质特征、矿床地球化学及Ｏ、Ｃ、Ｂ同位素特征的研究，结合数学地质方法分析认为辽东－吉南地区早元古代硼矿的成矿作用可分为沉积成岩成矿和变质－混合岩化改造成矿这两个主要成矿期。矿床成因类型为沉积变质改造型

GEOLOGICAL CHARACTERISTICS AND GENESIS OF EARLY PROTEROZOIC BORATE DEPOSITS IN EAST LIAONING SOUTH JILIN

In a certain sence of deposit type,the Early Proterozoic borate deposits in East Liaoning South Jinlin stand properly as the only reworked sedimentary borate type in the world. This arguement is supported by systematic researches on the deposits in terms of their borate geology, deposit geochemistry,and isotopic patterns of O, C and B elements with the help of mathematical geology. The borate mineralization developed in two stages: sedimentodiagenetic and metamigmatic. The former may be further divided into two substages, one, volcano ejecting,hot spring substage, during which B , Mg and Fe rich materials as hot folw or spring of volcanos were ejected up through constantly or intermittently active contemporaneous faults onto the sea floor into some restricted basins where ore forming elements like B were highly concentrated along with Mg, Fe and so on. The other, rock and ore forming substage, featured the evolution of the restricted basins which, under arid conditions,underwent from evaporation through concentration to successive precipitation of hydromagnesite (anhydrite), Mg borate (inderite, pinnoite, etc.) and the like,finally forming primary borate layers. The latter minerlizing stage, metamigmatic stage, was characteristic of a few impacts from regional metamorphism on the primary borate layers,namely, the upflowing hot currents derived from the metamorphism causing in these borate layers the recrystallization of some minerals, the dehydration of hydroborate minerlas and the reactivation and migration of ore forming materials. Late migmatization and structural deformation also exerted lots of influences on mineralization, to the effect that the primary borate undertook deformation, reactivation, migration, reenrichment and emplacement,terminating in partly thickened, highly graded deposits.