Research On The Regional Metallogenic System Of Borate Deposits In Eastern Liaoning Province, China

The borate deposits in Eastern Liaoning are,but its metallogenic time has not been wellconstrained yet. The metallogenic type and tectonic setting of the borate deposits are stillcontroversial. With the guidance of metallogenic system theory, based on field geologic survey,with the principal clue of the diagenetic and metallogenic isotope geochronology and petrologiclgeochemistry, by applying new technologies, new methods and new theories, and combiningwith the regional metallogenic geological background and its evolution to mineralizationresearch, the basic geology, the geology of mineral deposits, the metallogenic system andmineralization regularity are studied, and the metallogenic prediction is conducted.To determine the formation age of the borate deposit, the hi—solution SHRIMP methodwas utilized and it is the first time to acquire the protolith age of the hyalotourmalites as almost2170Ma, and the metamorphic age as around1900Ma. According to dating results, it isconcluded that the main metallogenic age wass around1900Ma, and the economic deposit wasfurther enriched with the assembly of the Rodinia supercontinent. The borate deposits haveexperienced repeated mineralization.Geochemistry of granitic rocks in Houxianyu district and Mg—rich marbles in Zhuanmiaodistrict is Systematically studied, showing that the bedded migmatite is formed by remelting andreplacing the sediments. The concealed boron—bearing series under the bedded migmatiteextends steadily, which defines the spacial structure of the borate deposit. The Mg—rich marbleshave the characteristics of magma causes, and the boron orebody is consistent with the strata ofmarbles and strictly restricted in occurrences.Based on the comprehensive study on geological features and other mineralization points,the metallogenic system of borate deposits in Eastern Liaoning is established preliminarily in thispaper after discussion on the basic elements of mineralization system, which is typicallysuperimposed metallogenic system. It is regarded that the Liao—Ji paleo—rift coupling with thedifferent geological process is the key on regional set of mineralization. The volcanic sedimentand hot spring brought huge quantity of B, Mg and Fe—bearing fluids from the mantle and thelower crust up into the ore—forming basins, which provides benefic geological conditions formineralization especially. Most of boron is from palaeoproterozoic formations, such as LiaoheGroup and so on. The ore—forming fluid mainly evolved from metamorphic hydrothermal, which replaces strongly with magnesian rocks that is the most important factor to lead to borondeposit from fluid. The widespread geothermal heating which was triggered by ColumbiaSupercontinent and Rodinia Supercontinent assembly has procided much energy formineralization. The interstratified sliding belts which were derived from the fold strucrures werenot only the transportation channel of boron—bearing fluid, but also the ore housing.According to the metallogenic system theory, it could be overally considered thestratabound deposits in multi—period and multi—genesis type of volcanic sedimentation beingsuperimposed by metamorphic—hydrothermal solution, which are related to the originalvolcanic(hydrothermal) sediment and subsequently experienced the multi—period regionalmetamorphism reformation, superposition of metamorphic hydrothermalism and also themineralization process of tectonomagmatism during the Indosinian—Yanshanian. Theredistribution and enrichment of metallogenetic element, caused by metasomatism with thedifferent ore—forming favourable rocks and the formation of multi—phase and multi—genesismetamorphic—hydrothermal solution, plays important roles in the development of borate deposit.Then the metallogenic regularity is summarized, and ore predication is made by the author andpreliminarily delineated4prospecting areas, which can be provided important scientific basis forfurther prospecting and exploration.