The early Oligocene beryl-bearing pegmatite in the Cuonadong dome，southern Tibet: Its forming mechanism and geological significances
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摘要: 错那洞穹隆位于特提斯喜马拉雅东段，发育钨锡-铍稀有金属成矿作用。错那洞穹隆由上（边部）、中（幔部）、下（核部）3个构造层组成，分别以上、下拆离断层为分界线，其中在幔部强变形带中发育一套同构造变形的含绿柱石花岗伟晶岩。锆石U-Pb年代学表明，该套伟晶岩形成于33.7±0.4Ma（MSWD=1.12），为早渐新世岩浆活动的产物，明显早于穹隆中目前发现的淡色花岗岩（20~14Ma）。岩石地球化学和Sr-Nd-Hf同位素测试结果显示：（1）错那洞早渐新世花岗伟晶岩为过铝质高钾富钠花岗质岩石，具有较高SiO2（>69.74%）、高Al2O3（>14.58%）及较低的CaO、MgO、MnO、TiO2的特征；（2）高场强元素及大离子亲石元素均呈现高度变化特征，富集轻稀土元素，亏损重稀土元素；（3）Sr同位素初始值（0.696308～0.751604）与Nd同位素初始值（-11.48～-12.05）总体在角闪岩与泥质片麻岩之间，εHf（t）值介于-5.4～0.1之间（主要集中在-5.4～-1.8）。综合研究表明，错那洞早渐新世含绿柱石伟晶岩是角闪岩与泥质片麻岩混熔的结果，其中泥质片麻岩的部分熔融起主导作用，其形成与藏南拆离系（STDS）的活动密切相关，表明错那洞地区新生代地壳深熔作用主要源岩在早渐新世已完成了从角闪岩向泥质片麻岩的转变。该同构造变形含绿柱石伟晶岩的发现，揭示错那洞穹隆的成穹作用至少在早渐新世便已开始。铍稀有金属可能在早渐新世已有了初始富集，而在中新世大规模岩浆活动中实现了巨量富集。Abstract: The large-scale tungsten-tin-beryllium mineralization was newly discovered in the Cuonadong Dome，which is located in the east of the Tethyan Himalaya. Cuonadong Dome was divided into the upper part (the edge)，the middle part (the mantle)，and the lower part (the core) by the upper and lower detachment faults. A set of syntectonic deformed beryl-bearing granitic pegmatite was occurred in the mantle，of which the rocks were strongly deformed. The zircon U-Pb isotopic data show that the pegmatite was formed at 33.7±0.4 Ma (MSWD=1.12)，which was the Early Oligocene magmatism and obviously older than the Miocene leucogranites(20-14Ma)in the Dome. The characteristics of the whole-rock geochemistry and isotopic geochemistry show that: (1) the Early Oligocene granitic pegmatite is the peraluminous granitic rock with high potassium and sodium. The characteristics of the major elements show that the granitic rocks have higher SiO2 (>69.74%) and Al2O3 (>14.58%)，lower CaO，MgO，MnO and TiO2than common granitic rocks; (2) high field strength elements(HFSE) and large ion lithophile elements (LILE) all exhibit high variation characteristics，enriching light rare earth elements and depleting heavy rare earth elements; (3) The values of the initial Sr isotope (0.696308～0.751604) and the initial Nd isotope (-11.48～-12.05) range between those of amphibolite and metapelites，and the values of zircon εHf(t) are between -5.4 and 0.1 (mainly concentrated in -5.4～-1.8). According to comprehensive research，the Early Oligocene beryl-bearing pegmatite was derived from the partial melting of source consisting dominantly of metapelites and subordinately amphibolite，which was related to the activities of the South Tibetan Detachment System (STDS)，and indicate that the primary partial melting source of the Cenozoic crustal anatexis in the Cuonadong Dome changed from amphibolite to metapelites at the Early Oligocene. The discovery of the syntectonic deformed beryl-bearing pegmatite reveals that the Cuonadong Dome began to form at least in the Early Oligocene. The initial enrichment of beryllium mineralization likely occurred in the Early Oligocene，whereas the giant enrichment occurred in the Miocene associated with Miocene leucogranites.
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Keywords:
- Cuonadong dome /
- pegmatite /
- partial melting /
- Tethyan Himalaya
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[1] 李德威, 刘德民, 廖群安,等.藏南萨迦拉轨岗日变质核杂岩的厘定及其成因[J]. 地质通报,2003,(5):303-307. [2] 张金阳,廖群安,李德威.西藏定结地区高喜马拉雅淡色花岗岩的地球化学特征与岩浆源区研究[J]. 地质科技情报,2003,(3):9-14. [3] 张进江,郭磊,张波. 北喜马拉雅穹隆带雅拉香波穹隆的构造组成和运动学特征[J]. 地质科学,2007,(1):16-30. [4] 高利娥,高家昊,赵令浩,等. 藏南拿日雍错片麻岩穹窿中新世淡色花岗岩的形成过程:变泥质岩部分熔融与分离结晶作用[J]. 岩石学报,2017,33(8):2395-2411. [5] 辜平阳,何世平,李荣社,等. 藏南拉轨岗日变质核杂岩核部花岗质片麻岩的地球化学特征及构造意义[J]. 岩石学报,2013,29(3):756-768. [6] Lee J,Hacker B R,Dinklage W S,et al. Evolution of the Kangmar Dome,southern Tibet:Structural,petrologic,and thermochronologic constraints[J]. Tectonics,2000,19(5):872-895.
[7] Lee J,Hacker B R,Wang Y. Evolution of North Himalayan gneiss Domes:structural and metamorphic studies in Mabja Dome,southern Tibet[J]. Journal of Structural Geology,2004,26(12):2297-2316.
[8] Lee J,Mcclelland W,Wang Y,et al. Oligocene-Miocene middle crustal flow in southern Tibet:geochronology of Mabja Dome[J]. Geological Society,London,Special Publications,2006,268(1):445-469.
[9] Lee J,Whitehouse M J. Onset of mid-crustal extensional flow in southern Tibet:Evidence from U/Pb zircon ages[J]. Geology,2007,35(1):45.
[10] Leech M L. Does the Karakoram fault interrupt mid-crustal channel flow in the western Himalaya[J]? Earth and Planetary Science Letters,2008,276(3):314-322.
[11] Zeng L S,Liu J,Gao L E,et al. Early Oligocene anatexis in the Yardoi gneiss Dome,southern Tibet and geological implications[J]. Chinese Science Bulletin,2009,54(1):104-112.
[12] Zeng L S,Gao L E,Xie K J,et al. Mid-Eocene high Sr/Y granites in the Northern Himalayan Gneiss Domes:Melting thickened lower continental crust[J]. Earth and Planetary Science Letters,2011,303(3-4):251-266.
[13] 高利娥,曾令森,刘静,等. 藏南也拉香波早渐新世富钠过铝质淡色花岗岩的成因机制及其构造动力学意义[J]. 岩石学报,2009,(09):2289-2302. [14] 高利娥,曾令森,谢克家. 北喜马拉雅片麻岩穹窿始新世高级变质和深熔作用的厘定[J]. 科学通报,2011,(36):3078-3090. [15] 高利娥,曾令森,侯可军,等. 藏南马拉山穹窿佩枯错复合淡色花岗岩体的多期深熔作用[J]. 科学通报,2013,(27):2810-2822. [16] 高利娥,曾令森,王莉,等. 藏南马拉山高钙二云母花岗岩的年代学特征及其形成机制[J]. 岩石学报,2014,29(6):1995-2012. [17] 张志,张林奎,李光明,等. 北喜马拉雅错那洞穹隆-片麻岩穹隆新成员与穹隆控矿新命题[J]. 地球学报,2017,38(5):754-766. [18] 张林奎,张志,李光明,等. 特提斯喜马拉雅错那洞穹隆的岩石组合、构造特征与成因[J]. 地球科学,2018,43(8):2664-2683. [19] 李光明,张林奎,焦彦杰,等. 西藏喜马拉雅成矿带错那洞超大型铍钨锡多金属矿床的发现及意义[J]. 矿床地质,2017,36(4):1003-1008. [20] Debon F,Fort P L,Sheppard S M F,et al. The Four Plutonic Belts of the Transhimalaya-Himalaya:a Chemical,Mineralogical,Isotopic,and Chronological Synthesis along a Tibet-Nepal Section[J]. Journal of Petrology,1986,27(1):219-250.
[21] Chen Z,Liu Y,Hodges K,et al. The Kangmar Dome:a metamorphic core complex in southern Xizang (Tibet)[J]. Science,1990,250(4987):1552-1556.
[22] Smit M A,Hacker B R,Lee J. Tibetan garnet records early Eocene initiation of thickening in the Himalaya[J]. Geology,2014,42(7):591-594.
[23] Zeng L S,Gao LE,Tang S H,et al. Eocene magmatism in the Tethyan Himalaya,southern Tibet[J]. Geological Society,London,Special Publications,2014,412:SP412. 8.
[24] Liu Z C,Wu F Y,Ding L,et al. Highly fractionated Late Eocene (~35 Ma) leucogranite in the Xiaru Dome,Tethyan Himalaya,South Tibet[J]. Lithos,2016,240-243:337-354.
[25] Schǎrer U,Xu RH,Allègre C J. U-(Th)-Pb systematics and ages of Himalayan leucogranites,south Tibet[J]. Earth and Planetary Science Letters,1986,77(1):35-48.
[26] Harris N,Massey J. Decompression and anatexis of Himalayan metapelites[J].Tectonics,1994,13(6):1537-1546.
[27] Harrison T M,Lovera O M,Grove M. New insights in to the origin of two contrasting Himalayan granite belts[J].Geology,1997,25(10):899-902.
[28] Zeng L S,Gao LE,Dong C Y,et al. High-pressure melting of metapelite and the formation of Ca-rich granitic melts in the Namche Barwa Massif,southern Tibet[J]. Gondwana Research,2012,21(1):138-151.
[29] 林彬,唐菊兴,郑文宝,等. 西藏错那洞淡色花岗岩地球化学特征、成岩时代及岩石成因[J]. 岩石矿物学杂志,2016,35(3):391-406. [30] Liu Z C,Wu FY,Ji WQ,et al. Petrogenesis of the Ramba leucogranite in the Tethyan Himalaya and constraints on the channel flow model[J]. Lithos,2014,208-209:118-136.
[31] Duan J L,Tang J X,Lin B. Zinc and lead isotope signatures of the Zhaxikang Pb Zn deposit,South Tibet:Implications for the source of the ore-forming metals[J]. Ore Geology Reviews,2016,78:58-68.
[32] Xie Y L,Li L M,Wang B G,et al. Genesis of the Zhaxikang epithermal Pb-Zn-Sb deposit in southern Tibet,China:Evidence for a magmatic link[J]. Ore Geology Reviews,2017,80:891-909.
[33] Zhou Q,Li WC,Qing CS,et al. Origin and tectonic implications of the Zhaxikang Pb-Zn-Sb-Ag deposit in northern Himalaya:evidence from structures,Re-Os-Pb-S isotopes,and fluid inclusions[J]. Mineralium Deposita,2017,1-16.
[34] 卿成实,丁俊,李应栩,等. 马扎拉金锑矿元素组合异常及找矿方向[J]. 金属矿山,2014, (12):134-137. [35] Zhang L K,Li G M,Santosh M,et al. Cambrian magmatism in the Tethys Himalaya and implications for the evolution of the Proto-Tethys along the northern Gondwana margin:Acase study and overview[J]. Geological Jounal,2018,1-21.
[36] Zhu D C,Pan G T,Mo X X,et al. Petrogenesis of volcanic rocks in the Sangxiu Formation,central segment of Tethyan Himalaya:A probable example of plume-lithosphere interaction[J]. Journal of Asian Earth Sciences,2007,29(2-3):320-335.
[37] Zhu D C,Chung S L,Mo X.,et al. The 132 Ma Comei-Bunbury large igneous province:Remnants identified in present-day southeastern Tibet and southwestern Australia[J]. Geology,2009,37(7):583-586.
[38] Zhu D C,Zhao Z D,Niu Y L,et al. The origin and pre-Cenozoic evolution of the Tibetan Plateau[J]. Gondwana Research,2013,23(4):1429-1454.
[39] 林彬,唐菊兴,郑文宝,等. 藏南扎西康矿区流纹岩的岩石地球化学、锆石U-Pb测年和Hf同位素组成[J]. 地质论评,2014,1:178-189. [40] Liu Z,Zhou Q,Lai Y,et al. Petrogenesis of the Early Cretaceous Laguila bimodal intrusive rocks from the Tethyan Himalaya:Implications for the break-up of Eastern Gondwana[J]. Lithos,2015,236-237:190-202.
[41] 胡古月,曾令森,高利娥,等. 藏南隆子地区恰嘎流纹质次火山岩稀土元素类似四分组效应[J]. 地质通报,2011,30(01):82-94. [42] Andersen T. Correction of common lead in U-Pb analyses that do not report 204Pb[J]. Chemical Geology,2002,192:59-79.
[43] Gao S,Liu XM,Yuan HL,et al. Analysis of forty-two major and trace elements of USGS and NIST SRM Glasses by LA-ICPMS[J]. Geostand Newsl.,2002,22:181-195.
[44] Wu FY,Yang YH,Xie LW,et al. Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology[J]. Chemical Geology,2006,234:105-126.
[45] 王银喜,顾连兴,张遵忠,等. 东天山晚石炭世大石头群流纹岩Sr-Nd-Pb同位素地球化学研究[J].岩石学报,2007,23(7):1749-1755. [46] Peccerillo A,Taylor SR. Geochemistry of Eocene calcalkaline volcanic rocks from the Kastamonu area,Northern Turkey[J]. Contributions to Mineralogy and Petrology,1976,58:63-81.
[47] Wright JB. A simple alkalinity ratio and its application to questions of non-orogenic granite genesis[J]. Geological Magmazine,1969,106:370-384.
[48] Boynton WV. Cosmochemistry of the earth elements:meteorite studies,Rare Earth element geochemistry[M].In:Henderson R(eds.),1984.
[49] Sun S S,McDonough W F. Chemical and isotopic systematic of oceanic basalts:Impliations for mantle composition and processes. Geological Society of London Special Publication 1989,42:313-345.
[50] Zhang H F,Harris N,Parrish R,et al. Causes and consequences of protracted melting of the mid-crust exposed in the North Himalayan antiform[J]. Earth & Planetary Science Letters,2004,228(1-2):195-212.
[51] Le Fort P. Manaslu leucogranite:A collision signature of the Himalaya:A model for its genesis and emplacement[J]. Journal of Geophysical Research,1981,86(B11):10545-10568.
[52] Schärer U,Xu R H,Allègre CJ. U-(Th)-Pb systematics and ages of Himalayan leucogranites,south Tibet[J]. Earth and Planetary Science Letters,1986,77(1):35-48.
[53] Simpson R L,Parrish R R,Searle M P,et al. Two episodes of monazite crystallization during metamorphism and crustal melting in the Everest region of the Nepalese Himalaya[J]. Geology,2000,28(5):403-406.
[54] Daniel C G,Hollister L S,Parrish R R,et al. Exhumation of the Main Central Thrust from lower crustal depths,Eastern Bhutan Himalaya[J]. Journal of Metamorphic Geology,2003,21(4):317-334.
[55] Searle M P,Simpson R L,Law R D,et al. The structural geometry,metamorphic and magmatic evolution of the Everest massif,High Himalaya of Nepal South Tibet[J]. Journal of the Geological Society,2003,160:345-366.
[56] Guo Z F,Wilson M. The Himalayan leucogranites:Constraints on the nature of their crustal source region and geodynamic setting[J]. Gondwana Research,2012,22(2):360-376.
[57] Gao L E,Zeng LS,A simow P D. Contrasting geochemical signatures of fluid-absent versus fluid-fluxed melting of muscovite in metasedimentary sources:The Himalayan leucogranites[J]. Geology,2017,45(1):39-42.
[58] 李旺超,张泽明,向华,等. 喜马拉雅造山带核部的变质作用与部分熔融:亚东地区高压泥质麻粒岩的岩石学与年代学研究[J]. 岩石学报,2015,31(5):1219-123. [59] King J,Harris N,Argles T,et al. Contribution of crustal anatexis to the tectonic evolution of Indian crust beneath southern Tibet[J]. GSA Bulletin,2011,123(1-2):218-239.
[60] Dostal J,Chatterjee A K. Contrasting behaviour of Nb/Ta and Zr/Hf ratios in a peraluminous granitic pluton (Nova Scotia,Canada)[J]. Chemical Geology,2000,163(1-4):207-218.
[61] Claiborne L L,Miller C F,Walker B A,et al. Tracking magmatic processes through Zr/H fratiosinrocks and Hf and Ti zoning in zircons:An example from the Spirit Mountain batholith,Nevada[J]. Mineralogical Magazine,2006,70:517-543.
[62] Patiño Douce A E,Harris N. Experimental constraints on Himalayan Anatexis[J]. Journal of petrology,1998,39:689-710.
[63] Atherton M P,Petford N. Generation of sodium-rich magmas from newly underplated basaltic crust[J]. Nature,1993,362:144-146.
[64] 张宏飞,N.Harris,R.Parrish,等. 北喜马拉雅萨迦穹窿中苦堆和萨迦淡色花岗岩的U-Pb年龄及其地质意义[J]. 科学通报,2004,(20):2090-2094. [65] Ding L,Kapp P,Wan X Q. Paleocene-Eocene record of ophiolite obduction and initial India Asiacollision,southcentral Tibet[J]. Tectonics,2005,24(3):TC3001,doi: 10.1029/2004TC001729.
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