Mineralization Model And Survey & Evaluation Of Early Proterozoic Mg-borate Deposits In East Liaoning

Borate Depoists are one vital kind of mineral resources in China. Its mineral products likeboric acid and borax are extensively used in chemical industry, metallurgy, aviatic industry,atomic energy industry, medicine, optical glass, rubber and construction materials, etc. So far in China the workable borate resources are szaibelyite-type borate deposits (so-called"white borate") in east Liaoning and brine borax in salines in Qinghai-Tibet Platean. Due to itspoor infrastructures in outlying areas, brine borax is mined at a limited capacity, less than 8% ofinternal market need, while borate deposits in east Liaoning offer 92%. The rapid-developing economy has a surging demand for borate minerals, which resulted ina shortage in borate reserve. In order to mitigate the shortage in borate resource and to ensure thesustainable development of economy, it is necessary to survey and explore more borate minerals.This dissertation studied the genesis of borate deposits in east Liaoning, assessed the boratepotential and then supplied a theoretical guide for surveying and exploring borate minerals.(1) Study on petrology reveals that boron-bearing sequences are formed under a limited riftenvironment and that boron-bearing Mg-peridotite originated from komatiite, a kind ofultrabasic effusive rocks.(2) Laminated migmatite as a boron-bearing formation is a consequence of regionalmigmatitization with magmatitization strength related to lithology of original rocks.(3) A mineralized model of borate deposits, established for east Liaoning based on boratemineralization, indicates that borate mineralization underwent two processes, first primaryenrichment and then partial melting migmatitization. The major mineralization factorsinclude primary enrichment of element boron, formation of Mg-bearing bedrock and partialmelting. Partial melting model can be simplified as follows: primary enrichment of elementboron & formation of Mg-bearing ultrabasic rocks → boron-bearing acid hydrotherm bymigmatizitization → Mg-bearing borate minerals via replacing Mg-bearing ultrabasic rocksor boron-bearing silicate minerals via replacing Al-bearing ultrabasic rocks.(4) A mineralization model, established for borate deposits in east Liaoning, can besummarized as laminated migmatite model and slide thrust structure model. A surveymodel shows that the chief survey indexes are marked by boron-bearing sequences,Mg-bearing ultrabasic rocks and migmatitization.(5) According to the theory above and survey practice, economic borate ore bodies werediscovered in Dashiqiao, Zhuanmiao (Kuandian County) and Yangmugan (KuandianCounty) areas, especially large-sized ore bodies were explored beneath granites in Yingkouarea, an important breakthrough;hence, migmatized granites are viewed as the topformation of boron-bearing sequences. Hidden ore bodies were explored in Lujiagou,Dongchagou, Erdaogou, Lujianangou and Banchangyu blocks where the surface is coveredwith migmatized granites, acquiring 250 kt of B2O3. Exploration work presently in Lujianangou block has conformed that borate ore bodies are125m long (not opened), 70m wide and 50m thick at a grade of B2O3 15.62-26.79%. It could bemost possibly a large borate deposit. The thickest szaibelyite body was explored in Banchangyublock, Dashiqiao County, 68.85m thick at a mean grade of B2O3 14.40%, a potential medium tolarge-sized szaibelyite deposit.