Cenozoic Tectono-Magmatic and Metallogenic Processes in the Sanjiang Region, Southwestern China
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EARTH-01992; No of Pages 32 Earth-Science Reviews 136 (2014) xxx–xxx Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Cenozoic tectono-magmatic and metallogenic processes in the Sanjiang region, southwestern China Jun Deng a,⁎,QingfeiWanga,b, Gongjian Li a,M.Santosha a State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China b Department of Geological Sciences, Indiana University, Bloomington, IN 47405, United States article info abstract Article history: The Sanjiang region in SE Tibet Plateau, and the western Yunnan region in southwestern China constitute a Received 2 December 2013 collage of Gondwana-derived micro-continental blocks and arc terranes that were accreted together after the Received in revised form 23 May 2014 closure of the Paleotethys Oceans in Permo-Triassic. The lithospheric structure in Sanjiang prior to the Cenozoic Accepted 24 May 2014 was dominantly characterized by sub-parallel sutures, subduction-modified mantle and crust, Mesozoic basins Available online 2 June 2014 between the sutures, and primary polymetallic accumulations. During the Cenozoic, intense deformation, episod- Keywords: ic magmatism, and diverse mineralization occurred, jointly controlled by the underthrust of South China litho- fi – Sanjiang sphere and the subduction of Paci c plate to the east, the India Eurasia continental collision and the Cenozoic subduction of Indian oceanic plate to the west. In this paper, we identify the following four main phases for India–Eurasia collision the Cenozoic evolution in the Sanjiang region. (i) Subduction and rollback of Neotethyan oceanic plate before Continent underthrust ca. 45–40 Ma caused lithosphere shortening, indicated by folding-thrusting in the shallow crust and horizontal Intracontinental metallogeny shearing in middle crust, and multiple magmatic activities, with associated formation of Sn ore deposits in the Tengchong block, Cu polymetallic ore deposits within Mesozoic basins, and Mo and Pb–Zn ore deposits in the Cangyuan area nearby the Changning–Menglian suture. (ii) Breakoff of Neotethyan slab in 45–40 Ma in combi- nation with the India–Eurasia continental hard collision caused the diachronous removal of the lower lithospher- ic mantle during 42–32 Ma, with the resultant potassic–ultrapotassic magmatism and formation of the related porphyry–skarn ore deposits along the Jinshajiang–Ailaoshan suture. (iii) Underthrusting of the South China plate resulting in the kinking of Sanjiang, expressed by block rotation, extrusion, and shearing in the southern Sanjiang during 32–10 Ma, with contemporary formation of the orogenic gold deposit along shear zones and the MVT Pb–Zn ore deposits within Mesozoic basins. (iv) Subduction of Indian oceanic plate possibly together with the Ninety East Ridge caused the local extension and volcanism in western Sanjiang, and the interplay be- tween India–Eurasia collision and the Pacific plate subduction induced tensile stress and mantle perturbation in eastern Sanjiang from ca. 10 Ma to present. The Cenozoic tectonic process traces a continuum of lithosphere shortening, sub-lithosphere mantle removal, and lithosphere underthrusting. During the lithospheric mantle removal, the simultaneous melting of the metasomatized lithospheric mantle and juvenile lower crust with possible metal enrichment contributed to the formation of potassic–ultrapotassic intrusive rocks and related porphyry–skarn mineralization. It is proposed that the kinking in the Sanjiang region was controlled by the non-coaxial compressions of the South China block and India continent, which are much larger in size than the blocks in Sanjiang. The underthrust continental lithosphere of the South China block caused the formation of orogenic gold deposits due to the release of metamorphic fluids from the front of the underthrust zone and the development of MVT Pb–Zn deposits via fluid circulation in the farther metal-enriched Mesozoic basins. Our study reveals that the pre-Cenozoic lithospheric structure in Sanjiang played an important role in the styles of tectonic movement, the nature and spatial distribution of magmatism, and the large-scale metallogeny during the Cenozoic. © 2014 Elsevier B.V. All rights reserved. Contents 1. Introduction............................................................... 2 2. Pre-Cenozoictectonicevolutionandframework............................................... 3 ⁎ Corresponding author. Tel./fax: +86 10 82322301. E-mail address: [email protected] (J. Deng). http://dx.doi.org/10.1016/j.earscirev.2014.05.015 0012-8252/© 2014 Elsevier B.V. All rights reserved. Please cite this article as: Deng, J., et al., Cenozoic tectono-magmatic and metallogenic processes in the Sanjiang region, southwestern China, Earth-Sci. Rev. (2014), http://dx.doi.org/10.1016/j.earscirev.2014.05.015 2 J. Deng et al. / Earth-Science Reviews 136 (2014) xxx–xxx 2.1. Tectonicblocks........................................................... 3 2.2. Suturesandmagmaticbeltsalongblockmargins........................................... 5 3. CenozoicorogenyinTibetandmantlearchitectureinSanjiang........................................ 5 3.1. OrogenyinTibet.......................................................... 5 3.2. MantlearchitectureinSanjiang................................................... 5 4. Crustdeformation............................................................. 6 4.1. Overallfeature........................................................... 6 4.2. Gaoligongshanshearzone...................................................... 8 4.3. Chongshanshearzone....................................................... 8 4.4. Ailaoshan–RedRivershearzone................................................... 8 4.5. DeformationintheMesozoicandCenozoicbasins........................................... 9 4.6. Regionaldeformationmodel.................................................... 9 5. Magmatism................................................................10 5.1. PaleocenetoEarlyEocenesubduction-relatedmagmatism.......................................10 5.2. MiddleEocenetoEarlyOligoceneintracontinentalmagmatism.....................................10 5.2.1. LateEoceneintraplatemagmatisminwesternSanjiang....................................10 5.2.2. Middle Eocene to Early Oligocene potassic–ultrapotassic igneous rocks along the Jinshajiang–Ailaoshantectonicbelt........12 5.3. Late Miocene–Holocenevolcanicrocks................................................12 5.3.1. Pliocene–HolocenevolcanicrocksintheTengchongblock...................................12 5.3.2. Plio-PleistocenevolcanicrocksinthesoutheasternSanjiang..................................17 6. Metallogenesis..............................................................17 6.1. Paleocene to Early Eocene magmatic–hydrothermaloredeposits....................................17 6.2. Middle Eocene to Early Oligocene ore deposits related to potassic–ultrapotassicintrusiverocks......................18 6.3. Oligocene MVT Pb–ZnpolymetallicoredepositsinMesozoicbasins...................................19 6.4. Oligoceneorogenicgolddeposits..................................................19 6.5. MiocenetoHolocenehotspring-relatedAuandGeoredeposits....................................20 7. Tectono-magmaticandmetallogenicevolution...............................................20 7.1. Paleocene–Eocene oceanic slab subduction-breakoff, lithospheric mantle removal, and porphyry–skarnoredeposits.............20 7.2. Oligocene continental underthrust and regional kinking: orogenic gold and MVT Pb–Zndeposits......................25 7.3. LateCenozoicevolution.......................................................26 7.4. Contributionofthepre-CenozoictectonicstoCenozoicprocesses....................................26 8. Concludingremarks............................................................27 Acknowledgments...............................................................27 AppendixA. Supplementarydata.......................................................27 References...................................................................27 1. Introduction type (MVT) Pb–Zn, and orogenic Au, were formed in Cenozoic, making the Sanjiang one of the most productive and potential regions for The Sanjiang (Three Rivers) region is named due to it is drained metal resources in China. These three genetic types of ore deposits in by three major rivers: the Jinshajiang, Lancangjiang and Nujiang. Sanjiang were produced in continental collisional setting, in contrast The region covers the southeastern part of the Tibet Plateau and to those formed along convergent plate margins associated with oceanic western Yunnan province in China (Fig. 1). The NS-trending subduc- plate subduction or along passive continental margins (Mitchell and tion zone of Indian oceanic plate and Ninety East Ridge represented Garson, 1981; Groves et al., 1998; Doglioni et al., 1999; Richards, by the Kerguelen hotspot formed at 130 Ma (Muller et al., 1993) 2003). Thus, the analysis of the Cenozoic tectonic evolution in Sanjiang occur to the west of the Sanjiang (Figs. 1 and 2). The subduction is important in understanding the interaction of multiple crustal blocks zones of the Phillipine Sea plate and Pacific plate are developed to and the nature and mechanism of the associated metallogeny. the southeast. The Cenozoic tectonic deformation, the magmatic and metallogenic The Sanjiang region