THE ACID-INTERMEDIATE INTRUSIVE ROCKS IN THE EAST SECTION OF MIDDLE QILIAN OROGENIC BELT: LA-ICP-MS Zircon U-Pb Age and Tectonic Implications
CAO Jin-shan, LI Wu-fu, WANG Guo-liang, ZHANG Xin-yuan
Key Laboratory of Geological Process and Mineral Resources in Northern Qinhai-Tibet Plateau/Qinghai Institute of Geological Survey, Xining 810012, China
Abstract:The acid-intermediate intrusions are developed in Shenjiaxia-Jiangou area in the east section of Middle Qilian Mountains, Qinghai Province. The field geological survey and petrographic study show that the intrusions occur in stock, mainly consisting of monzogranite and granodiorite which are in pulsation contact with each other. The LA-ICP-MS zircon U-Pb isotopic dating of 2 monzogranite samples gains the weighted average ages of 465.7±2.2 Ma (n=24, MSWD=0.031) and 459±2 Ma (n=21, MSWD=0.76) respectively, indicating that the intrusions were formed in Middle Ordovician. The lithogeochemical characteristics reveal that the intrusions belong to quasialuminous-peraluminous medium-high K calc-alkaline series with the (La/Yb)N of 10.57-23.126 and δEu of 0.47-0.69. The REE patterns show right-dipping "V" shaped curves. The LILEs such as Rb, Ba, Th, K, La, Ce, Sm and Nd are strongly enriched, Zr and Hf weakly enriched, while the HSFEs (Nb, Ta, P and Ti) are strongly depleted. The rocks are characterized by island arc magmatite, which may be related to the southward subduction of North Qilian Ocean.
曹锦山, 李五福, 王国良, 张新远. 中祁连东段乐都地区中酸性侵入岩LA-ICP-MS锆石U-Pb年龄及其构造意义[J]. 地质与资源, 2019, 28(5): 423-433.
CAO Jin-shan, LI Wu-fu, WANG Guo-liang, ZHANG Xin-yuan. THE ACID-INTERMEDIATE INTRUSIVE ROCKS IN THE EAST SECTION OF MIDDLE QILIAN OROGENIC BELT: LA-ICP-MS Zircon U-Pb Age and Tectonic Implications. GEOLOGY AND RESOURCES, 2019, 28(5): 423-433.
Song S G, Niu Y L, et al. Tectonics of the North Qilian orogen, NW China[J]. Gondwana Research, 2013,23(4):1378-1401.
[5]
Xiao W J, Windley F, Yong Y. Early Paleozoic to Devonian multiple-accretionary model for the QiLian Shan,NW China[J]. Journal of Asian Earth Sciences, 2009,35(3/4):323-333.
[6]
Xu Z Q, Yang J S, Wu C L, et al. Timing and mechanism of formation and exhumation of the Northern Qaidam ultrahigh-pressuremetamo rphic belt[J]. Journal of Asian Earth Sciences, 2006,28(2/3):160-173.
[7]
Yin A, Harrison T M. Geologic evolution of the Himalayan-Tibetan orogen[J]. Annual Review of Earth and Planetary Sciences, 2000,28(1):211-280.
[8]
Zhang J X, Meng F C, Wan Y S. A cold Early Palaeozoic subduction zone in the North QiLian Mountains, NW China:Petrological and U-Pb geochronological constraints[J]. Journal of metamorphic Geology, 2007,25(3):285-304.
[9]
Wu C L, Gao Y H, Frost B R, et al. An early Palaeozoic double-subduction model for the North QiLian oceanic plate:Evidence from zircon SHRIMP dating of granites[J]. International Geology Review, 2011,53(2):157-181.
[10]
Tseng C Y, Yang H J, Yang H Y, et al. Continuity of the North QiLian and North QinLing orogenic belts, Central Orogenic System of China:Evidence from newly discovered Paleozoic adakitic rocks[J]. Gondwana Research, 2009,16(2):285-293.
[11]
Xia L Q, Xia Z C, Xiu X Y. Magmagenesis in the ordovician backarc basins of the Northern QiLian Mountains, China[J]. Geological Society of America Bulletin, 2003,115(12):1510-1522.
[12]
Gehrels G E, Yin A, Wang X. Magmatic history of the northeastern Tibetan[J]. Journal of Geophysical Research-Solid Earth, 2003,108(B9):2423.
[13]
Cowgill E, Yin A, Harrison T M, et al. Reconstruction of the Altyn Tagh fault based on U-Pb geochronology:Role of back thrusts, mantle sutures, and heterogeneous crustal strength in forming the Tibetan Plateau[J]. Journal of Geophysical Research-Solid Earth, 2003,108(B7):2346.
[14]
Zhang H F, Zhang B R, Harris N, et al. U-Pb zircon SHRIMP ages, geochemical and Sr-Nd-Pb isotopic compositions of intrusive rocks from the Longshan-Tianshui area in the southeast corner of the Qilian orogenic belt, China:Constraints on petrogenesis and tectonic affinity[J]. Journal of Asian Earth Sciences, 2006,27(6):751-764.
[15]
Chen Y X, Song S G, Niu Y L, et al. Melting of continental crust during subduction initiation:A case study from the Chaidanuo peraluminous granite in the North Qilian suture zone[J]. Geochimica et Cosmochimica Acta, 2014,13(2):311-336.
[16]
冯益民,何世平. 祁连山大地构造与造山作用[M]. 北京:地质出版社,1996:13-20.
[17]
Manetti P, Peccerillo A, Poli G, et al. Petrochemical constraints on the models of Cretaceous-Eocene tectonic evolution of the Eastern Pontic chain(Turkey)[J]. Cretaceous Resrarch, 1983,4(2):159-172,195-6671.
Yan Z, Aitchison J, Fu C, et al. HuaLong Complex,South QiLian terrane:U-Pb and Lu-Hf constraints on Neoproterozoic micro-continental fragments accreted to the northern Proto-Tethyan margin[J]. Precambrian Research, 2015,266:65-85.
Rubatto D, Gebauer G, Compagnoni R. Dating of eclogite-facies zircons:The age of Alpine metamorphism in the Sesia-Lanzo Zone (Western Alps)[J]. Earth and Planetary Science Letters, 1999,16(7):141-158.
[23]
Rubatto D, Hermann J. Zircon formation during fluid circulation in eclogites (Monviso, Western Alps):Implications for Zr and Hf budget in subduction zones[J]. Geochimica et Cosmochimica Acta, 2003,67(12):2173-2187
[24]
Dubinska E, Bylinab P, Kozlowskia A, et al. U-Pb dating of serpentinization:Hydrothermal zircon from a metasomatic rodingite shell (Sudetic ophiolite, SW Poland)[J]. Chemical Geology, 2004, 20(3):183-203.
[25]
Liati A, Gebauer D. Constraining the pregrade and regrade P-T-t path of Eocene HP rocks by SHRIMP dating difference zircon domain:Inferred rated of heating-burial, cooling and exhumation for central Rhodope, northern Greece[J]. Contrib Minern Petrol,1999, 13(5):340-354.