藏南错那淡色花岗岩LA-MC-ICP-MS锆石U-Pb年龄、岩石地球化学及其地质意义
Age and geochemistry of the Cuona leucogranite in southern Tibet and its geological implications
-
摘要: 藏南错那淡色花岗岩位于喜马拉雅造山带的东部。对其进行LA-MC-ICP-MS锆石U-Pb定年,结果显示,结晶年龄为17.7±0.3Ma,代表中新世的地壳深熔作用。淡色花岗岩样品具有高的SiO2(74.46%~75.57%)、Al2O3(14.07%~14.64%)和K2O(4.19%~4.85%)含量,高的K2O/Na2O值(1.09~1.31)和A/CNK值(1.15~1.25),富集Rb、Th和U,亏损Ba、Nb、Sr、Zr等元素,显示高的Rb/Sr值(17.75~29.50)和强烈的负Eu异常(δEu=0.18~0.26),属于壳源成因的高钾钙碱性过铝质S型花岗岩。样品具有高的Isr值(0.78982~0.79276)和低的εNd(t)值(-19.5~-18.2),可与大喜马拉雅结晶杂岩(GHC)中的变泥质岩对比,暗示其来自变泥质岩的部分熔融。样品的Isr值较高,而Sr浓度较低,且随着Ba浓度的增加,Rb/Sr值逐渐降低,表明淡色花岗岩是无水条件下白云母部分熔融的产物,部分熔融可能与藏南拆离系(STDS)伸展拆离导致的构造减压有关。错那淡色花岗岩的形成反映了地壳伸展减薄背景下,构造减压导致的中下地壳中含水矿物脱水熔融,并沿STDS上升侵位的动力学过程。Abstract: The Cuona leucogranite pluton is situated in the east of Himalayan orogen. LA-MC-ICP-MS zircon U-Pb dating re-veals that leucogranites were crystallized at 17.7±0.3Ma, representing the Miocene crustal anataxis. Geochemical studies show that the samples are characterized by high SiO2(74.46%~75.57%), Al2O3(14.07%~14.64%), K2O(4.19%~4.85%), K2O/Na2O ratios(1.09~1.31) and A/CNK values(1.15~1.25), enrichment of Rb, Th, U and depletion of Ba, Nb, Zr, Sr, and high ratios of Rb/Sr(17.75~29.50) with strong negative Eu anomalies(δEu=0.18~0.26). These features suggest that they are crust-derived high potassium calcalkaline and peraluminous S-type granite. The relatively high Isr(0.78982~0.79276) and low εNd(t)(-19.5~-18.2) are well comparable with data of the metapelite from Greater Himalayan Crystalline complex(GHC), indicating that the leucogranites were generated from their partial melting. The features of high Isr and low Sr concentration as well as the decreasing Rb/Sr values with increasing Ba concentration demonstrate that the Cuona leucogranites were derived from muscovite dehydration melting under the water-absent condition, possibly triggered by structural decompression responding to the activity of South Tibetan Detachment system(STDS). It is held that the Cuona leucogranites reflect dynamics of structural decompression, dehydration melting and emplacement of the melt along STDS under the background of crustal extension and thinning.
-
Key words:
- Cuona leucogranite /
- LA-MC-ICP-MS /
- zircon U-Pb dating /
- Sr-Nd isotopes /
- formation mechanism /
- southern Tibet
-
-
[1] 吴福元, 刘志超, 刘小驰, 等.喜马拉雅淡色花岗岩[J]. 岩石学报, 2015, 31(1):1-36.
[2] Searle M P, Godin L.The South Tibetan Detachment system and the Manaslu leucogranite:a structural re-interpretation and restoration of the Annapurna Manaslu Himalaya, Nepal[J]. Journal of Geology, 2003, 111(5):505-523.
[3] Annen C, Scaillet B, Sparks R S J. Thermal constraints on the em-placement rate of a large intrusive complex:The Manaslu leucogranite, Nepal Himalaya[J]. Journal of Petrology, 2006, 47(1):71-95.
[4] Cottle J M, Jessup M J, Newell D L, et al. Structural insights into the early stages of exhumation along an orogen-scale detachment:The South Tibetan Detachment system, Dzakaa Chu section, eastern Himalaya[J]. Journal of Structural Geology, 2007, 29(11):1781-1797.
[5] Yang X Y, Zhang J J, Qi G W, et al. Structure and deformation around the Gyirong basin, north Himalaya, and onset of the south Tibetan detachment[J]. Science in China(Series D), 2009, 52(8):1046-1058.
[6] Larson K P, Godin L, Davis J D, et al. Out-of-sequence deformation and expansion of the Himalayan orogenic wedge:Insight from the Changgo culmination, south central Tibet[J]. Tectonics, 2010, 29(4):1-30.
[7] Leloup P H, Maheo G, Arnaud N, et al. The South Tibet detach-ment shear zone in the Dinggye area:Time constraints on extrusion models of the Himalayas[J]. Earth and Planetary Science Letters, 2010, 292(1/2):1-16.
[8] Chambers J, Parrish R R, Argles T, et al. A short-duration pulse of ductile normal shear on the outer South Tibetan detachment in Bhutan:Alternating channel flow and critical taper mechanics of the eastern Himalaya[J]. Tectonics, 2011, 30(2):TC2005. Doi:10.1029/2010TC002784.
[9] Liu X B, Liu X H, Leloup P H, et al. Ductile deformation within Upper Himalaya Crystalline Sequence and geological implications, in Nyalam area, Southern Tibet[J]. Chinese Science Bulletin, 2012, 57(26):3469-3481.
[10] Mitsuishi M, Simon R W, Aoya M, et al. E-W extension at 19 Ma in the Kung Co area, S.Tibet:Evidence for contemporaneous E-W and N-S extension in the Himalayan orogen[J]. Earth and Planetary Science Letters, 2012, 325/326:10-20.
[11] Yan D P, Zhou M F, Robinson P T, et al. Constraining the midcrustal channel flow beneath the Tibetan Plateau:Data from the Nielaxiongbo gneiss dome, SE Tibet[J]. International Geology Re-view, 2012, 54(6):615-632.
[12] 莫宣学, 赵志丹, 邓晋福, 等.印度-亚洲大陆主碰撞过程的火山作用响应[J]. 地学前缘, 2003, 10(3):135-148.
[13] Zhang J J, Santosh M, Wang X X, et al. Tectonics of the northern Himalaya since the India-Asia collision[J]. Gondwana Research, 2012, 21(4):939-960.
[14] Wang X X, Zhang J J, Liu J, et al. Middle-Miocene transforma-tion of tectonic regime in the Himalayan orogen[J]. Chinese Science Bulletin, 2013, 58(1):108-117.
[15] Edwards M A, Harrison T M. When did the roof collapse? Late Miocene north-south extension in the high Himalaya revealed by Th-Pb monazite dating of the KhulaKangrigranite[J]. Geology, 1997, 25(6):543-546.
[16] Coleman M E. U-Pb constraints on Oligocene-Miocene deforma-tion and anatexis within the Central Himalaya, Marsyandi valley, Nepal[J]. American Journal of Science, 1998, 298(7):553-571.
[17] Harrison T M, Grove M, Lovera O M, et al. A model for the ori-gin of Himalayan anatexis and inverted metamorphism[J]. Journal of Geophysical Research, 1998, 103(B11):27017-27032.
[18] Murphy M A, Harrison T M. Relationship between leucogranites and the Qomolangma detachment in the Rongbuk Valley, south Tibet[J]. Geology, 1999, 27(9):831-834.
[19] Schneider D, Edwards M, Kidd W S F, et al. Early Miocene anatex-is identified in the western syntaxis, Pakistan Himalaya[J]. Earth and Planetary Science Letters, 1999, 167(3/4):121-129.
[20] 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.
[21] Kellett D A, Godin L. Pre-Miocene deformation of the Himalayan superstructure, Hidden valley, central Nepal[J]. Journal of the Geo-logical Society, 2009, 166(2):261-275.
[22] Sachan H K, Kohn M J, Saxena A, et al. The Malari leucogranite, Garhwal Himalaya, northern India:Chemistry, age, and tectonic implications[J]. Geological Society of American Bulletin, 2010, 122(11/12):1865-1876.
[23] Daniel C, Vidal P, Fernandez A, et al. Isotopic study of the Manaslu granite(Himalaya, Nepal):Inferences of the age and source of Hi-malayan leucogranites[J]. Contributions to Mineralogy and Petrology, 1987, 96(1):78-92.
[24] Harris N, Inger S. Trace element modeling of pelite-derived gran-ites[J]. Contributions to Mineralogy and Petrology, 1992, 110(1):46-56.
[25] Harris N, Massey J. Decompression and anatexis of Himalayan metapelites[J]. Tectonics, 1994, 13(6):1537-1546.
[26] Guillot S, Le Fort P. Geochemical constraints on the bimodal origin of High Himalayan leucogranites[J].Lithos, 1995, 35(3/4):221-234.
[27] 杨晓松, 金振民, Huenges E, 等. 高喜马拉雅黑云斜长片麻岩脱水熔融实验:对青藏高原地壳深熔的启示[J]. 科学通报, 2001, 46(3):246-250.
[28] 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.
[29] Harris N, Ayres M, Massey J. Geochemistry of granitic melts pro-duced during the incongruent melting of muscovite:Implications for the extraction of Himalayan leucogranite magma[J]. Journal of Geophysical Research, 1995, 100(B8):15767-15777.
[30] Harrison T M, Lovera O M, Grove M. New insights into the ori-gin of two contrasting Himalayan granite belts[J]. Geology, 1997, 25(10):899-902.
[31] Le Fort P, Cuney M, Deniel C, et al. Crustal generation of the Hi-malayan leucogranite[J]. Tectonophysics, 1987, 134(1/2/3):39-57.
[32] Davidson C, Grujic D E, Hollister L S, et al. Metamorphic reac-tions related to decompression and synkinematic intrusion of leuco-granite,High Himalayan Crystallines, Bhutan[J]. Journal of Meta-morphic Geology, 1997, 15(5):593-612.
[33] Harrison T M, Grove M, McKeegan K D, et al. Origin and epi-sodic emplacement of the Manaslu intrusive complex, central Hi-malaya[J]. Journal of Petrology, 1999, 40(1):3-19.
[34] Nabelek P I, Liu M. Petrologic and thermal constraints on the ori-gin of leucogranites in collisional orogens[J]. Transactions of the Royal Society of Edinburgh:Earth Sciences, 2004, 95:73-85.
[35] 张进江.北喜马拉雅及藏南伸展构造综述[J]. 地质通报, 2007, 26(6):639-649.
[36] Aikman A B, Harrison T M, Ding L. Evidence for early(>44Ma) Himalayan crustal thickening, Tethyan Himalaya, southern Tibet[J]. Earth 牡?瑤栠敐?瑡敮捥?瑡潲湹椠捓?敩癥潮汣略琠楌潥湴?潥晲?琬栠攲‰匰漸甬琠栲?吴椨戱支琲愩渺??椭洲愳氮愼祢慲嬾?崳??吠斋捓瑈漬渠椠換獟???パら???金??咷??セキ自??ㄠ?二??活动时代[J]. 大地构造与成矿学, 2015, 39(2):250-259.
[37] Liu Y S, Gao S, Hu Z C, et al. Continental and oceanic crust recy-cling-induced melt-peridotite interaction in the Trans-North China Orogen U-Pb dating, Hf isotopes and trace elements in zir-con from mantle xezoliths[J]. Journal of Petrology, 2009, 51(1/2):537-571.
[38] Ludwig K R. User's manual for Isoplot 3.00:A geochronological toolkit for Microsoft Excel[J]. Berkeley Geochronology Center Spe-cial Publication, 2003, 4:1-70.
[39] Wu Y B, Zheng Y F. Genesis of zircon and its constraints on interpretation of U-Pb age[J]. Chinese Science Bulletin, 2004, 49(15):1554-1569.
[40] Sun S S, McDonough W F. Chemical and isotopic systematics of oceanic basalts:Implications for mantle composition and process[J]. Geological Society of London Special Publication, 1989, 42(1):313-345.
[41] Steiger R H, Jäger E. Subcommission on geochronology:Convention on the use of decay constants in geochronology and cosmo-chronology[J]. Earth and Planetary Science Letters, 1977, 36(3):359-362.
[42] Lugmair G W, Harti K. Lunar initial 143Nd/144Nd:Differential evo-lution of the lunar crust and mantle[J]. Earth and Planetary Science Letters, 1978, 39(3):349-357.
[43] Jahn B M, Wu F Y, Lo C H, et al. Crust-mantle interaction induced by deep subduction of the continental crust:Geochemical and Sr-Nd isotopic evidence from post-collisional mafic-ultramaf-ic intrusions of the northern Dabie complex, central China[J]. Chemistry Geology, 1999, 157(1/2):119-146.
[44] Harrison T M, Mckeegan K D, LeFort P. Detection of inherited monazite in the Manaslu leukogranite by 208Pb/232Th ion micro-probe dating-crystallization age and tectonic implication[J]. Earth and Planetary Science Letters, 1995, 133(3/4):271-282.
[45] Searle M P, Parrish R R, Hodges K V. Shisha Pangma leucogran-ite, south Tibetan Himalaya:Field relations, geochemistry, age, ori-gin, and emplacement[J]. Journal of Geology, 1997, 105(5):295-317.
[46] Hodges K, Bowring S, Davidek K, et al. Evidence for rapid dis-placement on Himalayan normal faults and the importance of tectonic denudation in the evolution of mountain ranges[J]. Geology, 1998, 26(6):483-486.
[47] 于俊杰, 曾令森, 刘静, 等.藏南定结地区早中新世淡色花岗岩的形成机制及其构造动力学意义[J]. 岩石学报, 2011, 27(7):1961-1972.
[48] Imayama T, Takeshita T, Yi K, et al. Two-stage partial melting and contrasting cooling history within the Higher Himalayan Crys-talline Sequence in the far-eastern Nepal Himalaya[J]. Lithos, 2012, 134/135:1-22.
[49] Kellett D A, Grujic D, Warren C, et al. Metamorphic history of a syn-convergent orogen-parallel detachment:The South Tibetan detachment system, Bhutan Himalaya[J]. Journal of Metamorphic Geology, 2010, 28(8):785-808.
[50] 杨晓松, 金振民.西藏亚东淡色花岗岩Rb-Sr和Sm-Nd同位素研究:关于其年龄和源岩的证据[J]. 地质评论, 2001,47(3):294-300.
[51] Knesel K M, Davidson J P. Insights into collisional magmatism from isotopic fingerprints of melting reactions[J]. Science, 2002,296(5576):2206-2208.
[52] Ahmad T, Harris N, Bickle M, et al. Isotopic constraints on the structural relationships between the Lesser Himalayan Series and the High Himalayan Crystalline Series, Garhwal Himalaya[J]. Geological Society of America Bulletin, 2000,112(3):467-477.
[53] Miller C, Thoni M, Frank W, et al. The early Paleozoic magmatic event in the Northwest Himalaya, India:Source, tectonic setting and age of emplacement[J]. Geological Magazine, 2001, 138(3):237-251.
[54] Richards A, Argles T, Harris N, et al. Himalayan architecture con-strained by isotopic tracers from clastic sediments[J]. Earth and Plan-etary Science Letters, 2005, 236(3/4):773-796.
[55] Gao L E, Zeng L S. Fluxed melting of metapelite and the forma-tion of Miocene high-CaO two-mica granites in the Malashan gneiss dome, southern Tibet[J]. Geochimicaet Cosmochimica Acta, 2014, 130:136-155.
[56] Gehrels G E, DeCelles P G, Ojha T P, et al.Geological and U-Pb geochronological evidence for early Paleozoic tectonism in the Dadeldhura thrust sheet, far-west Nepal Himalaya[J]. Journal of Asian Earth Sciences, 2006, 25(4/5/6):385-408.
[57] 张宏飞, Harris N, Parrish R, 等. 北喜马拉雅淡色花岗岩地球化学:区域对比、岩石成因及构造意义[J]. 地球科学, 2005, 30(3):275-288.
[58] 王晓先, 张进江, 闫淑玉, 等. 北喜马拉雅恰芒巴二云母花岗岩的年龄及形成机制[J]. 地质科学, 2015, 50(3):708-727.
[59] PatiñoDouce A, Harris N. Experimental constraints on Himalayan anatexis[J]. Journal of Petrology, 1998, 39(4):689-710.
[60] Zeng L S, Asimow P, Saleeby J B. Coupling of anatectic reactions and dissolution of accessory phases and the Sr and Nd isotope sys-tematics of anatectic melts from a metasedimentary source[J]. Geo-chimicaet Cosmochimica Acta, 2005, 69(4):3671-3682.
[61] Zeng L S, Gao L E, Xie K J, et al. Mid-Eocene high Sr/Y granites in the Northern Himalayan Gneiss Domes:Melting thickening lower continental crust[J]. Earth and Planetary Science Letters, 2011, 303(3/4):251-266.
[62] Inger S, Harris N. Geochmical constraints on leucogranite magmatism in the Langtang Valley, Nepal Himalaya[J]. Journal of Petrolo-gy, 1993, 34(2):345-368.
[63] Liu Z C, Wu F Y, Ji W Q, et al. Petrogenesis of the Rambaleuco-granite in the Tethyan Himalayan and constraints on the channel flow model[J]. Lithos, 208/209:118-136.
[64] Lee J, Whitehouse M. Onset of mid-crustal extensional flow in southern Tibet:Evidence from U/Pb zircons age[J]. Geology, 2007, 35(1):45-48.
[65] King J, Harris N, Argles T, et al. Contribution of crustal anatexis to the tectonic evolution of Indian crust beneath southern Tibet[J]. Geological Society of America Bulletin, 2011, 123(1/2):218-239.
[66] 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, 58(27):2810-2822.
[67] Catlos E J, Harrison T M, Manning C E, et al. Records of the evo-lution of the Himalayan orogen from in situ Th-Pb ion micro-probe dating of monazite:eastern Nepal and western Garhwal[J]. Journal of Asian Earth Science, 2002, 20(5):459-479.
[68] Cottle J M, Jessup M J, Newell D L, et al. Geochronology of granu-litized eclogite from the AmaDrime Massif:implications fo
-
计量
- 文章访问数: 1147
- PDF下载数: 214
- 施引文献: 0