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福建永安县李坊重晶石矿床是特大型受变质沉积矿床。围岩为寒武纪浅变质(绿片岩相,黑云母带)硅、泥质夹砂屑正常沉积岩系,经受两期变质作用和至少4期变形作用。主变质期(D_1)发生在先,伴生与层理(S_0)平行的千枚状构造(S_1)。主变形期(D_2)发生在后,形成SN向、缓倾伏、倒转的I_c—Ⅱ型复武褶皱, 在千枚岩类中伴生肉眼上可见的视连续劈理,对S_0,S_1发生强烈的置换作用,致使区域地质构造长期被误认为单斜岩层,矿层中出现的小褶皱和寄生褶皱被误认为同生揉皱,反复褶皱的两个矿层被描写成多层序的,连续性差的几百个小矿体。笔者通过先构造后地层的工作程序,利用人工露头,观测各期各类构造形迹的产状、特征及其相互关系。划分构造模式、建立构造系列,测制了矿段构造—岩性地质图、并依据各期各类构造形迹的空间关系编制钻孔地质构造剖面图,预测地下矿层的廷伸情况和展布规律。继而进行几百个薄片的显微构造研究,并借助电镜扫描、岩组分析等手段,从微观上进一步揭示了变形与变质的关系,分析了各期褶皱和次生叶理的特征,相互关系,演化规律和成因问题。
Yong’an County, Fujian Li Fang barite deposit is a large-scale metamorphic sedimentary deposits. Surrounding rocks are Cambrian super-metamorphic (greenschist facies, biotite) siliciclastic and shaly intercalated sandstone normal sedimentary rocks that undergo two stages of metamorphism and at least 4 stages of deformation. The main metamorphism (D_1) occurs in the first, associated with stratigraphic (S_0) parallel to the teratoid structure (S_1). After the main deformation period (D_2) occurred, SN-trending, overturned and inverted I-c-Ⅱ type of complex folds were formed, and continuous cleavage accompanied by macroscopic appearance was observed in the phyllite. Strong S_0 and S_1 occurred , The regional geological structure has been mistakenly identified as monoclinic rock formation for a long time. The small folds and parasitic folds appearing in the seam are mistakenly identified as co-crumpling. The two layers of repeated folds are described as multi-sequence, with poor continuity Hundreds of small ore bodies. By constructing post-formation work procedures and using artificial outcrops, the author observed the occurrences, characteristics and interrelationships of various types of structural features in various periods. Divided the tectonic model, established the tectonic series, and measured the ore-section structure-lithology and geology map. Based on the spatial relations of various types of structural features in different periods, the borehole geological structure profiles were prepared to predict the extension and distribution of underground ore layers . Then the microstructures of hundreds of sheets were studied. The relationship between deformation and metamorphism was further revealed microscopically by means of electron microscope scanning and petrographic analysis. The characteristics of folds and secondary leaf foliations at different stages were analyzed. , The law of evolution and cause of the problem.