摘要
西藏甲玛铜多金属矿床以夕卡岩-角岩型为主,与驱龙斑岩铜矿床毗邻,是冈底斯成矿带东段两颗璀璨的明珠,最具代表性的世界级特大型多金属矿床。矿床内主要出露下白垩统林布宗组沙板岩和上侏罗统多底沟组灰岩,矿化发生于岩体与上侏罗统多底沟组接触带附近,以及和岩浆热液导通的多底沟组和林布宗组界线的层间破碎带,矿体整体呈上陡下缓似层状,矿化中心显示NNE向的雁列型排布。矿床围岩蚀变发育,以热接触蚀变和热交代蚀变为主,具相似的水平蚀变分带和垂向蚀变分带。
矿床中酸性斑岩的类型主要有花岗斑岩、花岗闪长斑岩、二长花岗斑岩、(石英)闪长玢岩,其中花岗斑岩主要分布于矿床南端,以岩珠状整体呈近EW向主动侵位围岩褶皱核部,矿物以填隙状的白云母为标志,显示强过铝质S型花岗岩特征,属于高钾钙碱性岩石系列;花岗闪长斑岩、二长花岗斑岩、(石英)闪长玢岩主要分布于铜山-则古郎地区,以岩脉(枝)近SN向雁列型被动侵位围岩,岩石中普遍发育岩浆混合现象,显示偏铝质I型花岗岩特征,属于中-高钾钙碱性C型埃达克岩。
甲玛似埃达克岩表现埃达克岩-钙碱性岩的演化系列,整体表现为Fe、Mg矿物的分异。随着岩浆酸度的增加,主元素只有w(K2O)含量增高,为正常岩浆演化序列。在演化过程中,甲玛似埃达克岩岩浆与基性岩浆发生了三次不同程度的岩浆混合作用,对应矿床的三期Cu、Mo成矿作用过程。
甲玛似埃达克岩的形成于亚洲-印度板块的“后碰撞”造山过程中,是该时期构造-岩浆-成矿活动的集中体现。其源区显示深部岛弧岩浆岩变质为角闪岩相后部分重熔,并受到富集地幔(EMⅡ)的混合作用的特征。甲玛似埃达克岩的形成过程可以描述如下:在14Ma前后,随着软流圈的大规模上涌,冈底斯地壳快速减薄,形成近南北向的正断层及裂陷盆地系统(墨竹工卡-错那裂谷)。在底侵玄武质岩浆房(可能来自EMⅡ)的加热作用下,导致更为上层的地壳部分熔融(角闪岩相的岛弧岩浆),形成似埃达克岩岩浆。伴随着底侵玄武质岩浆的侵位,似埃达克质岩浆与基性岩浆发生不同程度的岩浆混合作用,从而导致矿质的萃取与富集,随着混合岩浆结晶分异的持续进行,矿质不断从岩浆中分馏出进入流体系统,并沿近NS向的张性构造破碎带中沉淀、成矿。
JiaMa copper polymetallic deposits of Tibet which is a hornfels-skarn type deposit locates at the eastern of Gangdese metallogenic belt. It is adjacent to the QuLong porphyry copper deposit. The stratums of deposit are mainly Limbuzong group of the lower Cretaceous and duodigou group of the upper Jurassic. The Ore body is located between the two stratums as like-layered. The mineralized center have NNE trend arranged in echelon-type The wall rock alteration of deposit is developed, whit the similar horizontal and vertical alteration zoning
The main types of medium-acid porphyry in Jiama deposit are granite porphyry, granodiorite porphyry, monzogranite porphyry and (quartz) diorite porphyry. The granite porphyry arranged in EW are mainly distributed in the southern. The rock is charactered as muscovite, classified as strongly peraluminous S-type granite, also as high-K calc-alkaline series rocks. The other porphyry arranged in NS as echelon-type, classified as metaluminous I-type granite, also as medium-high-K calc-alkaline and C-type adakites.
Jiama adakites show the evolutionary trend of from adakites to calc-alkaline rock, that is the fractionation of Fe, Mg mineral. With the crystallization differentiation, all the main elements content reduce except the w(K2O), consistent with the normal magma evolution sequence. In the process of evolution ,there are three magma mingling processes between JiaMa adakites and basic magma, corresponding to the three Cu、Mo mineralization.
The formation of the Jama adakite-like rock is under the "post-collision" orogeny between the Asian and the Indian plates, which is the concentrated expression of the tectonics, the magmatism and the mineralization during that period. The source shows that the ignerous and metamorphic rock in the deep arc is amphibolite face through partial remelting , and mixed by the enriched mantle (EMⅡ).The formation process can be described like this : around 14Ma, with the large-scale asthenospheric upwelling and the rapid thinning of the crust Gangdese, the nearly N-S normal faults and the rift basin system formed. Under the heating of the underplating basaltic magma chamber, the upper crust (the island-arc magma of amphibolite face partially melted, and finally there resulted in the formation of the adakite-like rock. With the emplacement of underplating basaltic magma, there were different degrees of magma mixing between the adakite-like rock and the basic magma, which leading to the extraction and enrichment of the mineral. With the the mixed magma crystallization and differentiation continuing, the mineral separated from the magma affluxed into the fuild system, and precipitated and mineralized in the nearly N-S tensile frature zones .
引文
[1]曲晓明,侯增谦,黄卫.冈底斯斑岩铜矿(化)带:西藏第二个“玉龙”铜矿带[J].矿床地质, 2001,20(4):355-366.
[2]李光明,王高明,高大发,黄志英,姚鹏.西藏冈底斯铜矿资源前景与找矿方向[J].矿床地质.2002,21(增刊):144-147.
[3]李光明,杨家瑞,丁俊.西藏雅鲁藏布江成矿区矿产资源评价新进展[J].地质通报.2003, 22(9):699-703.
[4]何文渊,李江海,钱祥麟,郑多明.西藏冈底斯岛弧及其铜多金属矿带的基本特征与远景评估[J].地质通报.2002,21(1):35~40.
[5]王小春,晏子贵,周维德,等.初论西藏冈底斯带中段尼木西北部斑岩铜矿地质特征[J].地质与勘探,2002,38 (1):5~8.
[6]郑有业,王保生,樊子珲.西藏冈底斯东段构造演化与铜多金属成矿潜力分析[J].地质科技情报,2002,21 (2):55~60.
[7]侯增谦,曲晓明,黄卫.等.冈底斯斑岩铜成矿带有望成为西藏第二条玉龙铜矿带[J].中国地质.2001,28:27-29.
[8]侯增谦,莫宣学,高永丰,等.埃达克岩:斑岩铜矿的一种可能的重要含矿母岩-以西藏和智利斑岩铜矿为例.矿床地质. 2003, 22(1):0001-0012.
[9]黄志英,李光明.西藏雅鲁藏布江成矿区斑岩型铜矿基本特征与找矿潜力[J].地质与勘探.2004,40(1):1-6.
[10]曲晓明,杨岳清,李佑国,2004.从赋矿岩系岩石类型的多样性论羊拉铜矿的成因.矿床地质,23(4):431-442.
[11]曲晓明,侯增谦,国连杰,等.冈底斯铜矿带埃达克质含矿斑岩的源区组成与地壳混染:Nd、Sr、Pb、O同位素制约[J].地质学报,2004,78(6):813-821.
[12]曲晓明,侯增谦,唐绍华.义顿岛弧带弧后区板内岩浆作用的时代及意义.岩石矿物学杂志[J].2003,22:131-137.
[13]侯增谦,莫宣学,高永丰,等.埃达克岩:斑岩铜矿的一种可能的重要含矿母岩-以西藏和智利斑岩铜矿为例[J].矿床地质. 2003, 22(1):0001-0012.
[14]李金祥,秦克章,李光明,杨列坤.冈底斯中段尼木斑岩铜矿田的K-Ar、40Ar/39Ar年龄:对岩浆-热液系统演化和成矿构造背景的制约[J].岩石学报.2007, 23(5): 953-966.
[15] Kay RW.Aleutian magnesian andesites: Melts from subducted Pacific Ocean crust [J]. Volcanol, Geothern, Res.1978, 4:117-132.
[16] Defant M J, D rummond M S. Derivation of some modern arc magmas by melting of young subducted lithosphere [J].Nature.1990,347:662-665.
[17]张旗,王焰,熊小林,李承东.埃达克岩和花岗岩-机遇与挑战[M].2009.
[18]李武显,李献华.蛇绿岩中的花岗质岩石成因类型与构造意义[J].地球科学进展.2003, 18(3):392-397.
[19]刘敦一,简平,张旗,等.内蒙古图林凯蛇绿岩中埃达克岩SHRIMP测年:早古生代洋壳消减的证据[J].地质学报.2003, 77(3):317-327.
[20]简平,刘敦一,张旗,等.蛇绿岩及蛇绿岩中浅色岩的SHRIMP U-Pb测年[J].地学前缘.2003, 10(4):439-356.
[21] DeCelles,P.G,Robinson,D.M, and Zandt,G.Implications of shortening in the Himalayan foldthrust belt for uplift of the Tibetan Plateau,Tectonics,2002,V.21(6).
[22] Kohn, M., and Parkinson, C.D., 2002, Petrologic case for Eocene slab breakoff during the Indo-Asian collision: Geology, v. 30, p. 591–594.
[23]应丽娟,唐菊兴,王登红,等.西藏甲玛铜多金属矿床矽卡岩中辉钼矿铼-锇同位素定年及其成矿意义[J].岩矿测试.2009, 28(3):265-268.
[24] Kay RW.Aleutian magnesian andesites: Melts from subducted Pacific Ocean crust [J].Volcanol, Geothern, Res.1978, 4:117-132.
[25] Yin A , Harrison T M and Ryerson F J.Tertiary structural evolution of the Gangdes thrust system , southeastern Tibet [J] .Geophys, Res.1994,99:175~201.
[26] Yin, A., Harrison, T.M., 2000. Geologic evolution of the Himalayan-Tibetan orogen. [J]. Ann. Rev. Earth Planet. Sci. 28, 211–280.
[27] Blisniuk, P.M., Hacker, B.R., Glodny, J., Ratschbacher, L., Bi, S., Wu, Z, McWilliams, M.O., Calvert, A., 2001. Normal faulting incentral Tibet since at least 13.5 Myr ago. Nature 412, 628–632.
[28] Chung,S,-L,Liu,D,Ji,J,Chu,M,-F,Lee,H,-Y,Wen,D,J,Lo,C,H,Lee,T,Y,Qian,Q,Zhang,Q. Adakites from continental collision zones: melting of thickened lower crust beneath southern Tibet[J], Geology.2003,31:1021–1024.
[29] Zhang, J., Ding, L., 2003. East-west extension in Tibetan Plateau and its significance to tectonic evolution. Chin [J]. Geol. 38, 179–189 (in Chinese with English abstract).
[30] Hou Z Q, Gao Y F, Qu X M, Rui ZY and Mo X X. Origin of adakitic intrusives generated during mid-Miocene east-extension in south Tibet [J], Earth Planet, Sci.2004, 220:139-155.
[31] Williams, H,M,Turner, S,P,Pearce, J,A,Kelley, S,P,Harris, N,B,W.Nature of the source regions for post-collisional, potassic magmatism in Southern and Northern Tibet from geochemical variations and inverse trace element modeling[J].Petrol.2004, 45:555–607.
[32] Mo Xuanxue, Niu Yaoling, Dong Guochen et al. Contribution of syncollisional felsic magmatism to continental crust growth: A case study of the Paleogene Linzizong volcanic Succession in southern Tibet [J]. Chemical Geology. 2008,250, 49-67.
[33] Mo Xuanxue, Zhao Zhidan, Deng Jinfu et al. Petrology and geochemistry of postcollisional volcanic rocks from the Tibetan plateau: Implications for lithosphere heterogeneity and collision-induced asthenospheric mantle flow [J]. Geological Society of America , Special Paper 2006,409: 508-530
[34]莫宣学,董国臣,赵志丹,等.西藏冈底斯带花岗岩的时空分布特征及地壳生长演化信息[J].高校地质学报.2005,11(3):281-290.
[35]侯增谦,莫宣学,杨志明,王安建,潘桂棠,曲晓明,聂凤军.青藏高原碰撞造山带成矿作用:构造背景、时空分布和主要类型[J].中国地质.2006b, 33:348~359.
[36] Hou Z Q, Zhao Z D, Gao Y F, etal. Tearing and dischronal subduction of the Indian continental slab: Evidence from Cenozoic Gangdese volcano-magmatic rocks in south Tibet[J], Acta Petrologica Sinica.2006,22(4),761-774
[37]莫宣学,赵志丹,周肃,等.印度-亚洲大陆碰撞的时限[J].地质通报.2007, 26(10): 1240-1245.
[38] Harrsion T M,Copeland P, Kidd W S F,et al.Raising Tibet[J].Science.1992,255:1663~1670.
[39]杜光树,姚鹏,潘凤雏,等.喷流成因矽卡岩与成矿-以西藏甲马铜多金属矿床为例[M].成都:四川科学技术出版社.1998.82~113.
[40]李光明,芮宗瑶,王高明,等.西藏冈底斯成矿带甲马和知不拉铜多金属矿床的Re-Os同位素年龄及其意义[J],矿床地质. 2005, 24 (5) :481~489.
[41]曲晓明,侯增谦,唐绍华.义顿岛弧带弧后区板内岩浆作用的时代及意义[J].岩石矿物学杂志.2003,22:131-137.
[42]孟祥金,侯增谦,等.冈底斯斑岩铜矿成矿时限:邦浦矿床辉钼矿Re-Os同位素证据[J].矿床地质.2003, 21: 246-252.
[43]王亮亮,莫宣学,李冰,等.西藏驱龙斑岩铜矿含矿斑岩的年代学与地球化学[J].岩石学报.2006,22(4)。
[44]李金祥,秦克章,李光明,杨列坤.冈底斯中段尼木斑岩铜矿田的K-Ar、40Ar/39Ar年龄:对岩浆-热液系统演化和成矿构造背景的制约[J].岩石学报.2007, 23(5): 953-966.
[45] Pearce, J.A. and Mei Houjun, 1988. Volcanic rocks of the 1985 Tibet Geotraverse: Lhasa to Golmud. Phil. Trans [R]. Soc. Lond. A327:169-201.
[46] Turner, S., Hawke worth, C., Liu, J., Rogers, N., Kelley, S., van Calsteren, P., 1993. Timing of Tibetan uplift constrained by analysis of volcanic rocks [J]. Nature 364, 50–54.
[47] Turner, S., Arnaud, N., Liu, J., Rogers, N., Hawke worth, C., Harris, N.Kelley, S., van Calsteren, P., Deng, W., 1996. Post-collision, shoshonitic volcanism on the Tibetan Plateau: implications for convective thinning of the lithosphere and the source of ocean island basalts [J].Petrol. 37, 45–71.
[48] Miller C, Schuster R and Klotzli U, et al. Post-collisional potassic and ultrapotassic magmatismin SWTibet: geochemical and Sr-Nd-Pb-O isotopic constraints for mantle source characteristics and petrogenesis [J].Journal of Petrology, 1999, 40(9):1399~1424.
[49] Guo, Z., Hertogen, J., Liu, J., Pasteels, P., Boven, A., Punzalan, L., He, H., Luo, X., Zhang, W., 2005. Potassic magmatism in western Sichun and Yunnan provinces, SE Tibet, China: petrological and geochemical constraints on petrogenesis [J]. Petrol. 46, 33–78.
[50] Guo, Z., Wilson, M., Liu, J., Mao, Q., 2006. Post-collisional, potassic and ultrapotassic magmatism of the northern Tibetan Plateau: constraints on characteristics of the mantle source, geodynamic setting and uplift mechanisms [J]. Petrol. 47, 1177–1220.
[51] Thieblemont D, Stein G, Lescuyer J L. Gisements epithermaux porphyriques: la connexion adakite [J].Earth Planet.Sci.1997, 325:103~109.
[52] Bellon H , Yumul J r G P1Miocene to Quaternary adakites and related rocks in western Philippine arc sequences [J].Earth and Planetary Sciences ,2001 ,333 :343-350
[53]王强,许继峰,赵振华.强烈亏损重稀土元素的中酸性火成岩(或埃达克质岩)与Cu、Au成矿作用[J].地学前缘.2003.10(4):561-572.
[54]唐菊兴,王登红,等.西藏自治区墨竹工卡县甲玛矿区外围铜多金属矿详查[M].2009
[55]苟金.对拉萨地区叶巴组时代归属的新认识.西藏地质[J].1994.
[56]阴家润,苟金,裴树文.拉萨地块叶巴组内中侏罗世双壳类动物群及其古地理意义[J] .1998(2).
[57]毛国政.胡敬仁.谢尧武.拉萨地区叶巴组的特征及形成环镜[J] .2002.
[58]佘宏全,丰成友,张德全,等.西藏冈底斯中东段矽卡岩铜-铅-锌多金属矿床特征及成矿远景分析[J].矿床地质. 2005,24 (5):508~520。
[59]佘宏全,丰成友,张德全,等.西藏冈底斯铜矿带甲玛夕卡岩型铜多金属矿床与驱龙斑岩型铜矿流体包裹体特征对比研究[J].岩石学报.2006, 22(03):689-696.
[60]连玉,徐文艺,杨丹,等.西藏冈底斯甲玛和南木矿床流体包裹体SR-XRF研究.岩石矿物学杂志.2008, 3(27):185-198.
[61]冯孝良,管仕平,牟传龙,等.西藏甲马铜多金属矿床的岩浆热液交代成因:地质与地球化学证据[J].地质地球化学.2001,29(4):40~48.
[62] A Ludwig K R. Using Isoplot/EX, version3.23, A Geolocronolgical Toolkit for Microsoft Excel. Berkeley: Berkeley [J]. Geochronological Center Special Publication, 1999, 47.
[63] Ross R. Large, J. Bruce Gemmell and Holger Paulick. The Alteration Box Plot: A Simple Approach to Understanding the Relationship between Alteration Mineralogy and Lithogeochemistry Associated with Volcanic-Hosted Massive Sulfide Deposits. Economic Geology. 2001, 96(5):957-971.
[64] Peccerillo R, Taylor S R.Geochemistry of eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey. Contrib. Mineral Petrol., 1976, 58:63~81.
[65] Middlemost E A K. Magmas and Magmatic [M] Rocks. London: Longman.1985, 1~266.
[66]肖庆辉,邓晋福,马大铨,等.花岗岩研究思维与方法[M].地质出版社.2002.
[67]邓晋福,莫宣学,赵海玲,等.中国东部岩石圈根/去根作用与大陆“活化”.现代地质[M].1994, 8(3):349-356.
[68] Taylor, S.R., and McLennan, S.M., 1985. The Continental Crust: It’s Composition and Evolution: Oxford (Blackwell Scientific).
[69]路远发,GeoKit:一个用VBA构建的地球化学工具软件包[J],地球化学,2004,33(5):459-464.
[70] Sun, S-S. & McDonough, W.F.Chemical and isotopic systematic of oceanic basalts: implications for mantle composition and processes. Geological Society,,London,Special Publications .1989,2,313-345
[71] AGUE JJ AND BRIMHALL GH. 1988b. Magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of California: effects of assimilation, crustal thickness, and depth of crystallization. Geol Soc Amer Bull 100: 912-927.
[72]朱弟成,段丽萍,廖忠礼,潘桂棠.两类埃达克岩(Adakite)的判别[J].矿物岩石,2002,3(22):5-9.
[73] Pat?no D. A. E.What do experiments tell us about the relative contributions of crust and mantle to the origin of granitic magmas? In Castro, A., Fernandez, C., Vigneressese, J.L (Eds).Understanding granites: integrating new and classical techniques [J]. Geol. Soc. Lond. Spec. Publ., 1999, 168: 55-75.
[74] Maniar P D and Piccoli P M.Tectonic discrimination of granitoids [J].Geol Soc Am Bull,1989,101:635-643.
[75] Pearce J A, Harris N B W and Tindle A G. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks [J]. Journal of Petrology, 1984, 25:956-983.
[76] Rapp P R,Watson E B and Miller C F. Partial melting of amphibolite/sclogite and the origin of Archean trondhjemite and tonalities [J].Precambrian Res. 1991,51:1-25.
[77] Pearce J A and Parkinson I J.Trace element models for mantle melting: Application to volcanic arc petrogenesis, Magmatic Processes in Plate Tectonics [J], Geological Society of London, UK.1993, 373-404.
[78] Zindle A and Hart S R.Chemical geodynamics [J].Annu. Rev.Earth Plane, .Sci. Lett, 1986, 14:493~573.
[79] R E Zartman and B R Doe.Plumb tectonics-the model [J]. Tectonophysics.1981, 75:135~162.
[80] Baker et al., 1997 J.A. Baker, M.A. Menzies, M.F. Thirwal and C.G. McPherson, Petrogenesis of Quaternary intraplate volcanism, Sana’a Yemen: implications for plume–lithosphere interaction and polybaric melt hybridization, Journal of Petrology 38 (1997), pp. 1359–1390.
[81] Koprubasi, N, Aldanmaz, E.Geochemical constrains on the pathogenesis of CenozoicⅠ-type granitites in northwest Anatolia ,Turkey : Evidence for magma generation by lithospheric delamination in a post-coalitional setting. International Geology Review. 2004, 46:705 - 729.
[82]袁万明,侯增谦,李胜荣,等.西藏甲马多金属矿区热历史的裂变径迹证据[J].中国科学D辑.2001,31 (S1) :117~121.
[83]梁华英,喻亨祥,莫继海.西藏冈底斯矿带成矿作用及远景分析.矿物岩石地球化学通[J]报.2008, 27(3):289-293.
[84] Ray, G.E., and Webster, I.C.L., 1995, The Geochemistry of Mineralized Skarns in British Columbia, in Geological Fieldwork 1994, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1995-1, pages 371-383.
[85] Porfirio J.Pinto-Linares,Gilles Levresse,etal.Transitional adakite-like to cala-alkaline magmas in a continental extensional setting at La Paz Au-Cu Skarn deposits ,Mesa Central,Mexico:Metallogenic implications [J].Revista Mexicana de Ciencias Geologicas.2008, 25(1):39-58.
[86] Robin N.Armstrong.The Ore forming Potential of Cala Alkaline Systems: A Magmatic Perspective [M].University of Southampton, 1999.
[87] Jean Schroeder Cline, Robert J.Bodnar.Can Economic Porphyry Copper Mineralization be Generared by a Typicial Calc-Alkaline Melt? [J] Journal of Geophysical Research, 1991, 96(B5):8113-8126.