TY - JOUR
T1 - Birth, life, and demise of the Andean–syn-collisional Gissar arc
T2 - Late Paleozoic tectono-magmatic-metamorphic evolution of the southwestern Tian Shan, Tajikistan
AU - Worthington, James R.
AU - Kapp, Paul
AU - Minaev, Vladislav
AU - Chapman, James B.
AU - Mazdab, Frank K.
AU - Ducea, Mihai N.
AU - Oimahmadov, Ilhomjon
AU - Gadoev, Mustafo
N1 - Funding Information:
This project was funded by the NSF Tectonics Program (NSF-EAR-1419748) and ExxonMobil, as well as small grants from the Geological Society of America, the American Association of Petroleum Geologists, the Coney fund, and the Conoco Philips scholarship. This manu script benefited from insightful discus sions with Lothar Ratschbacher, Alexandra Käßner, Bradley Hacker, Jiba Ganguly, Mark Barton, George Gehrels, Mark Pecha, Andrew Kylander-Clark, Andrew Laskowski, Simon Stickroth, and Linglin Zhong. Fieldwork would not have been possible without the enthu siasm of Lucia Angiolini, Andrea Zanchi, and Evgeny Kanaev. We thank the Arizona Laserchron Center (NSF-EAR-1338583), the Michael J. Drake Electron Microprobe Laboratory, and University of California, Santa Barbara Laser-Ablation Split-Stream Petrochronology Lab for analytical support. Thoughtful reviews by D. Konopelko, Yu. S. Biske, A. Khudoley (Associate Editor), and J. Geissman (Editor) refined our understanding of the Tian Shan, enabling us to more judiciously interpret and integrate our data set into the late Paleozoic context of this intriguing orogen. The data for this paper are available in the supporting information and by contacting J. Worthington (jamesworthing-ton@email.arizona.edu).
Publisher Copyright:
©2017. American Geophysical Union. All Rights Reserved.
PY - 2017/10
Y1 - 2017/10
N2 - The amalgamation of the Central Asian Orogenic Belt in the southwestern Tian Shan in Tajikistan is represented by tectono-magmatic-metamorphic processes that accompanied late Paleozoic ocean closure and collision between the Karakum-Tarim and Kazakh-Kyrgyz terranes. Integrated U-Pb geochronology, thermobarometry, pseudosection modeling, and Hf geochemistry constrain the timing and petro-tectonic nature of these processes. The Gissar batholith and the Garm massif represent an eastward, along-strike increase in paleodepth from upper-batholith (~21–7 km) to arc-root (~36–19 km) levels of the Andean–syn-collisional Gissar arc, which developed from ~323–288 Ma in two stages: (i) Andean, I-type granitoid magmatism from ~323–306 Ma due to northward subduction of the Gissar back-arc ocean basin under the Gissar microcontinent, which was immediately followed by (ii) syn-collisional, I-S-type granitoid magmatism in the Gissar batholith and the Garm massif from ~304–288 Ma due to northward subduction/underthrusting of Karakum marginal-continental crust under the Gissar microcontinent. A rapid isotopic pull-up from ~288–286 Ma signals the onset of juvenile, alkaline-syenitic, post-collisional magmatism by ~280 Ma, which was driven by delamination of the Gissar arclogite root and consequent convective asthenospheric upwelling. Whereas M–HT/LP prograde metamorphism in the Garm massif (650–750°C/6–7 kbar) from ~310–288 Ma was associated with subduction-magma inundation and crustal thickening, HT/LP heating and decompression to peak-metamorphic temperatures (~800–820°C/6–4 kbar) at ~288 ± 6 Ma was driven by the transmission of a post-collisional, mantle-derived heat wave through the Garm-massif crust.
AB - The amalgamation of the Central Asian Orogenic Belt in the southwestern Tian Shan in Tajikistan is represented by tectono-magmatic-metamorphic processes that accompanied late Paleozoic ocean closure and collision between the Karakum-Tarim and Kazakh-Kyrgyz terranes. Integrated U-Pb geochronology, thermobarometry, pseudosection modeling, and Hf geochemistry constrain the timing and petro-tectonic nature of these processes. The Gissar batholith and the Garm massif represent an eastward, along-strike increase in paleodepth from upper-batholith (~21–7 km) to arc-root (~36–19 km) levels of the Andean–syn-collisional Gissar arc, which developed from ~323–288 Ma in two stages: (i) Andean, I-type granitoid magmatism from ~323–306 Ma due to northward subduction of the Gissar back-arc ocean basin under the Gissar microcontinent, which was immediately followed by (ii) syn-collisional, I-S-type granitoid magmatism in the Gissar batholith and the Garm massif from ~304–288 Ma due to northward subduction/underthrusting of Karakum marginal-continental crust under the Gissar microcontinent. A rapid isotopic pull-up from ~288–286 Ma signals the onset of juvenile, alkaline-syenitic, post-collisional magmatism by ~280 Ma, which was driven by delamination of the Gissar arclogite root and consequent convective asthenospheric upwelling. Whereas M–HT/LP prograde metamorphism in the Garm massif (650–750°C/6–7 kbar) from ~310–288 Ma was associated with subduction-magma inundation and crustal thickening, HT/LP heating and decompression to peak-metamorphic temperatures (~800–820°C/6–4 kbar) at ~288 ± 6 Ma was driven by the transmission of a post-collisional, mantle-derived heat wave through the Garm-massif crust.
KW - Carboniferous
KW - Central Asian Orogenic Belt
KW - Gissar arc
KW - Permian
KW - Tian Shan
KW - postcollisional magmatism
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U2 - 10.1002/2016TC004285
DO - 10.1002/2016TC004285
M3 - Article
AN - SCOPUS:85034212307
VL - 36
SP - 1861
EP - 1912
JO - Tectonics
JF - Tectonics
SN - 0278-7407
IS - 10
ER -