煎茶岭韧性剪切带特征及其对金矿的控制作用
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摘要
研究区位于秦岭造山带与上扬子被动陆缘之间摩天岭微地块东端的勉(县)—略(阳)—阳(平关)三角区。区内的煎茶岭金矿床是我国为数不多的与超基性岩有关的大型矿床之一。本论文是在对前人资料综合整理与分析的基础上,进行野外调研和室内测试,详细研究了韧性剪切带的变形及显微构造,分析了韧性剪切带的几何学、运动学和动力学特征,探讨了韧性剪切带的特征及其对金矿的控制作用。主要工作成果可概括为以下几点:
1、研究区内出露NWW向区域韧性剪切带和NE向区域韧性剪切带。NWW向区域韧性剪切带西起金洞子,东至张家山,北部以F_147断层为界,南部以F_18断层为界,长度大于10km,宽度一般2.6km。NE向区域韧性剪切带北起超基性岩南分支岩体,南至略阳组北的震旦系不整合面,沿走向至庙儿垭,长度从煎茶岭到断头崖出露约为6km,宽度从九道拐到柳树沟出露约为400m。两区域韧性剪切带内不同地段出露的动力变质岩主要有糜棱岩化岩石、初糜棱岩、糜棱岩、超糜棱岩和构造片岩等。
2、结合NWW、NE两区域韧性剪切带的几何学、运动学、动力学特征,说明它们呈共轭产出。早期,NWW向区域韧性剪切带为张扭性右行剪切,NE向区域韧性剪切带为张扭性左行剪切,σ_1≈280°∠10°,古应力值约93.7MPa;晚期,随着脆性程度进一步增加,NWW向区域韧性剪切带经历了压扭性左行剪切,NE向区域韧脆性剪切带经历了压扭性右行剪切,σ_1≈124°∠16°,古应力值约88.7MPa。
3、煎茶岭金矿床主要可分为东矿带、南矿带和北矿带。其中,东矿带位于超基性岩体东部,南矿带位于超基性岩体与围岩接触带的东南部,北矿带位于超基性岩体与围岩接触带的东北部。地球化学研究表明,超基性岩曾发生过强烈的热流体地质作用,含金脆韧性剪切带中有大量的流体加入,形成含H_2O~+矿物蚀变作用;南北矿带矿体的形成发生于同一期热液活动,在金成矿过程中,由花岗斑岩带来的热液和成矿物质主要起叠加富集作用。
4、煎茶岭金矿控矿构造位于NE向韧性剪切带北界与NWW向韧性剪切带南界相互交叉区上盘的超基性岩体与白云质糜棱岩接触带附近的韧脆性剪切带之中,是NWW向韧性剪切带进一步演化的产物。矿体均呈透镜状右行排列,出露于控矿韧脆性剪切带倾角由陡变缓部位,倾角大于70°时含金较低。何家岩金矿蚀变白云质糜棱岩矿体与中曼金矿蚀变糜棱岩化蛇纹岩型矿体实为一个矿体,是在韧脆性剪切和后期F_1~(45)断层左行剪切作用下向左发生位移约500m错开造成的;张家山金矿北部蚀变白云质糜棱岩矿体与南部蚀变糜棱岩化菱镁岩或蛇纹岩型矿体也是一个矿体,是在韧脆性剪切和后期F_1~(45)断层左行剪切作用下向左发生位移约300m错开造成的。
The prospecting area is located in Mian-lve-yang triangle area in easthern Motianlin Block between qinling orogenic zone and Yangtze Landmass,and Gold deposit of Jianchaling has the close relation with ultrabasic rock in this area, also is the rare golden ore deposit type in our country.This paper is based on the comprehensive analysis of the previous data, field work and indoor test. This paper has studied the deformation and features of the microstructures of shear zone in detail, analyzed the features of geometry, kinematics and dynamics of ductile shear zones, and discussed the characteristics of ductile shear zones and its control to gold deposit. The main conclusions are as follows:
1. The NWW and NE ductile shear zone had been founded in prospecting area.The NWW ductile shear zone west to Jindongzi,east to Zhangjiashan,north to F_1~(47) and south to F_1~8,with a length of 10km and width of 2.6km.The NE ductile shear zone north to the south of ultrabasic rock,south to unconformity surface in Sinian system north of Lveyang Formation.Belong the strike to Miaoerya the length of NE ductile shear zone is 6km from Duantouya to Jianchaling,and 400m in width from Jiudaoguai to Liushugou. The types of dynamic metamorphic rock containing mylonitization rock, protomylonite, mylonite,ultramylonite and tectonic schist in two ductile shear zone.
2. Comparison between the features of geometry, kinematics and dynamics of NWW and NE ductile shear zones, show that the two ductile shear zones has conjugate relation.In early stage the NWW ductile shear zones deformationed on the extensional of left handed and the NE ductile shear zones deformationed on the extensional of right handed, the maximum compressional stress orientation isσ_1≈280°∠10°and paleo-stress is about 93.7Mpa,in last stage the NWW ductile shear zones deformationed on the stress of right handed and the NE ductile shear zones deformationed on the stress of left handed, the maximum compressional stress orientation isσ_1≈124°∠16°andpaleo-stress is about 88.7Mpa.
3. Jianchaling gold deposits are divided into east,west and north ore belts based on the position with ultrabasic rock.The geochemical study show that ultrabasic rock had altered by strongly hydrothermal, Mass hydrothermal flows through gold-containing ductile shear zones and formed the aiteration by H_2O~+,the north and south ore zone formed in same stage hydrothermal process, in the mineralization process of Au, the hydrothermal and metallogenic material formed in granite-porphyry can increase the concentration of Au.
4. JIANCHALING gold ore-controlling structure are located with ductile shear zone ,and the ductile shear zone is occurrenced at the contact zone of the Jianchaling ultrabasic rock mass and dolomitic mylonite.Jianchaling gold deposit evolve into production of ductile shear zone.Orebodies were line with the right lens and expose with ore-controlling ductile shear zone.And when the Inclination of zone over 70°,it is very low gold content.Hejiayan and Zhongman gold deposit are caused by ductile-brittle shear and faults left Shearing about 500m.Hangjiashan golddeposits and Serpentinite-type orebodies aare caused by ductile-brittle shear and faults left Shearing about 300m.
1、研究区内出露NWW向区域韧性剪切带和NE向区域韧性剪切带。NWW向区域韧性剪切带西起金洞子,东至张家山,北部以F_147断层为界,南部以F_18断层为界,长度大于10km,宽度一般2.6km。NE向区域韧性剪切带北起超基性岩南分支岩体,南至略阳组北的震旦系不整合面,沿走向至庙儿垭,长度从煎茶岭到断头崖出露约为6km,宽度从九道拐到柳树沟出露约为400m。两区域韧性剪切带内不同地段出露的动力变质岩主要有糜棱岩化岩石、初糜棱岩、糜棱岩、超糜棱岩和构造片岩等。
2、结合NWW、NE两区域韧性剪切带的几何学、运动学、动力学特征,说明它们呈共轭产出。早期,NWW向区域韧性剪切带为张扭性右行剪切,NE向区域韧性剪切带为张扭性左行剪切,σ_1≈280°∠10°,古应力值约93.7MPa;晚期,随着脆性程度进一步增加,NWW向区域韧性剪切带经历了压扭性左行剪切,NE向区域韧脆性剪切带经历了压扭性右行剪切,σ_1≈124°∠16°,古应力值约88.7MPa。
3、煎茶岭金矿床主要可分为东矿带、南矿带和北矿带。其中,东矿带位于超基性岩体东部,南矿带位于超基性岩体与围岩接触带的东南部,北矿带位于超基性岩体与围岩接触带的东北部。地球化学研究表明,超基性岩曾发生过强烈的热流体地质作用,含金脆韧性剪切带中有大量的流体加入,形成含H_2O~+矿物蚀变作用;南北矿带矿体的形成发生于同一期热液活动,在金成矿过程中,由花岗斑岩带来的热液和成矿物质主要起叠加富集作用。
4、煎茶岭金矿控矿构造位于NE向韧性剪切带北界与NWW向韧性剪切带南界相互交叉区上盘的超基性岩体与白云质糜棱岩接触带附近的韧脆性剪切带之中,是NWW向韧性剪切带进一步演化的产物。矿体均呈透镜状右行排列,出露于控矿韧脆性剪切带倾角由陡变缓部位,倾角大于70°时含金较低。何家岩金矿蚀变白云质糜棱岩矿体与中曼金矿蚀变糜棱岩化蛇纹岩型矿体实为一个矿体,是在韧脆性剪切和后期F_1~(45)断层左行剪切作用下向左发生位移约500m错开造成的;张家山金矿北部蚀变白云质糜棱岩矿体与南部蚀变糜棱岩化菱镁岩或蛇纹岩型矿体也是一个矿体,是在韧脆性剪切和后期F_1~(45)断层左行剪切作用下向左发生位移约300m错开造成的。
The prospecting area is located in Mian-lve-yang triangle area in easthern Motianlin Block between qinling orogenic zone and Yangtze Landmass,and Gold deposit of Jianchaling has the close relation with ultrabasic rock in this area, also is the rare golden ore deposit type in our country.This paper is based on the comprehensive analysis of the previous data, field work and indoor test. This paper has studied the deformation and features of the microstructures of shear zone in detail, analyzed the features of geometry, kinematics and dynamics of ductile shear zones, and discussed the characteristics of ductile shear zones and its control to gold deposit. The main conclusions are as follows:
1. The NWW and NE ductile shear zone had been founded in prospecting area.The NWW ductile shear zone west to Jindongzi,east to Zhangjiashan,north to F_1~(47) and south to F_1~8,with a length of 10km and width of 2.6km.The NE ductile shear zone north to the south of ultrabasic rock,south to unconformity surface in Sinian system north of Lveyang Formation.Belong the strike to Miaoerya the length of NE ductile shear zone is 6km from Duantouya to Jianchaling,and 400m in width from Jiudaoguai to Liushugou. The types of dynamic metamorphic rock containing mylonitization rock, protomylonite, mylonite,ultramylonite and tectonic schist in two ductile shear zone.
2. Comparison between the features of geometry, kinematics and dynamics of NWW and NE ductile shear zones, show that the two ductile shear zones has conjugate relation.In early stage the NWW ductile shear zones deformationed on the extensional of left handed and the NE ductile shear zones deformationed on the extensional of right handed, the maximum compressional stress orientation isσ_1≈280°∠10°and paleo-stress is about 93.7Mpa,in last stage the NWW ductile shear zones deformationed on the stress of right handed and the NE ductile shear zones deformationed on the stress of left handed, the maximum compressional stress orientation isσ_1≈124°∠16°andpaleo-stress is about 88.7Mpa.
3. Jianchaling gold deposits are divided into east,west and north ore belts based on the position with ultrabasic rock.The geochemical study show that ultrabasic rock had altered by strongly hydrothermal, Mass hydrothermal flows through gold-containing ductile shear zones and formed the aiteration by H_2O~+,the north and south ore zone formed in same stage hydrothermal process, in the mineralization process of Au, the hydrothermal and metallogenic material formed in granite-porphyry can increase the concentration of Au.
4. JIANCHALING gold ore-controlling structure are located with ductile shear zone ,and the ductile shear zone is occurrenced at the contact zone of the Jianchaling ultrabasic rock mass and dolomitic mylonite.Jianchaling gold deposit evolve into production of ductile shear zone.Orebodies were line with the right lens and expose with ore-controlling ductile shear zone.And when the Inclination of zone over 70°,it is very low gold content.Hejiayan and Zhongman gold deposit are caused by ductile-brittle shear and faults left Shearing about 500m.Hangjiashan golddeposits and Serpentinite-type orebodies aare caused by ductile-brittle shear and faults left Shearing about 300m.
引文
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[4] 陈强,杨兴科,张连昌等.东天山脆—韧性变形转换与金矿带.新疆地质,2001:19(2):115-118.
[5] 邓军,翟裕生,杨立强等,论剪切带构造成矿系统.现代地质.1998,12(4):493-500.
[6] 董法先.陈柏林.李秀珍安徽界岭金矿及其外围成矿控矿构造与找矿方向1993(2).:30.
[7] 何永年,林传勇,史兰斌.1988.构造岩石学基:北京:地质出版社.
[8] 胡建明,董广法.2002.略阳县煎茶岭金矿矿体的空间展布规律及找矿方向.大地构造与成矿学,26(1):37-45.
[9] 胡玲.1998.显微构造地质学概论.北京:地质出版社.
[10] 黄婉康,甘先平,单祖翔,陈荔湘,刘雁.1996.陕西煎茶岭金矿区的岩石及成矿时代研究.地球化学,25(2):150-156.
[11] 李元,金世昌,俞广钧.云南墨江金矿床的同位素地球化学及成因探讨.地质地球化学1998,26(4).
[12] 凌井生,陈础廷,季明钧.河台韧性剪切带蚀变糜棱岩型金矿的地质特征、矿床成因与成矿模式,1992(3).
[13] 吕古贤等.构造物理化学与金矿成矿预测[M].北京:地质出版社,1999.1-457.
[14] 马华东,贺卫东,涂其军.2008.新疆东天山地区塔水河韧性剪切带特征.大地构造与成矿学,32(1):1-10.
[15] 庞春勇,陈民扬.1993.煎茶岭地区同位素地质年龄数据及其地质意义.床产与地质,7(5):354-360.
[16] 秦克令,何世平,宋述光.碧口地体同位素年代学及其意义[J].西北地质科学,1992,13(2):97-109.
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