Research Article| July 01, 2017 Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence Zhang Zeming; Zhang Zeming † 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China2Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100085, China †zzm2111@sina.com Search for other works by this author on: GSW Google Scholar Xiang Hua; Xiang Hua 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Search for other works by this author on: GSW Google Scholar Ding Huixia; Ding Huixia 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Search for other works by this author on: GSW Google Scholar Dong Xin; Dong Xin 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Search for other works by this author on: GSW Google Scholar Gou Zhengbin; Gou Zhengbin 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Search for other works by this author on: GSW Google Scholar Tian Zhulin; Tian Zhulin 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Search for other works by this author on: GSW Google Scholar M. Santosh M. Santosh 3School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing, 100083, China4Department of Earth Sciences, The University of Adelaide, Adelaide, SA 5005, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Zhang Zeming † 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China2Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100085, China Xiang Hua 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Ding Huixia 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Dong Xin 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Gou Zhengbin 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China Tian Zhulin 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China M. Santosh 3School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing, 100083, China4Department of Earth Sciences, The University of Adelaide, Adelaide, SA 5005, Australia †zzm2111@sina.com Publisher: Geological Society of America Received: 01 Jun 2016 Revision Received: 29 Nov 2016 Accepted: 04 Jan 2017 First Online: 06 Jul 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 2017 Geological Society of America GSA Bulletin (2017) 129 (7-8): 869–885. https://doi.org/10.1130/B31586.1 Article history Received: 01 Jun 2016 Revision Received: 29 Nov 2016 Accepted: 04 Jan 2017 First Online: 06 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Zhang Zeming, Xiang Hua, Ding Huixia, Dong Xin, Gou Zhengbin, Tian Zhulin, M. Santosh; Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence. GSA Bulletin 2017;; 129 (7-8): 869–885. doi: https://doi.org/10.1130/B31586.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Greater Himalayan Sequence and leucogranite forming the core of the Himalayan orogen provide an excellent natural laboratory in which to study processes related to crustal melting, granitoid formation, and the tectonic evolution of mountain belts. In contrast to most previous studies, which considered the Himalaya-aged granitoids as leucogranites, here we report a Miocene orbicular diorite from the Greater Himalayan Sequence in the east-central Himalaya. The diorite consists of ellipsoidal orbicules in a diorite matrix. The orbicules have a diorite core with or without garnet-sillimanite-biotite schist enclaves, an inner shell of tangentially oriented biotite laths, and an outer shell of radial or plumose plagioclase crystals. The diorite is aluminous and calcic, shows a fractionated rare earth element pattern with a strongly positive Eu anomaly, and has elevated Sr concentration. The schist enclaves underwent high-temperature metamorphism and partial melting under conditions of 9.2–12 kbar and 765–900 °C, followed by a retrograde pressure-temperature path of decompression and cooling. The inherited magmatic cores, metamorphic mantles, and magmatic rims of zircon from the diorite yield a protolith age of ca. 494 Ma, metamorphic ages ranging from ca. 26 Ma to 22 Ma, and melt crystallization ages of ca. 18–14 Ma. The inherited magmatic cores of zircon show variable but mostly negative εHf(t) values, whereas the metamorphic mantles and the magmatic rims of zircon yield variable and lower εHf(t) values. Our study shows that the orbicular diorite is a plagioclase + biotite + cordierite cumulate rock that formed by the fractional crystallization of peraluminous melt, which was generated by mixing of melts derived from the partial melting of both early Paleozoic granitoids and old pelitic rocks. The orbicular diorite and the trapped metapelitic schist have a prolonged high-temperature metamorphic, anatectic, and crystallization history that was initiated at ca. 26 Ma and lasted until ca. 14 Ma. The formation of orbicular structures was probably related to decompression during the ascent of anatectic melt, and subsequent rapid cooling. Melt mixing was also a key factor that aided in the formation of the orbicular structure of the diorite. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
