| Title | Petrogenesis and tectonic implications of cambrian Nb-enriched I- and aluminous A-type granites in the North Qilian suture zone |
| Authors | Chen, Yuxiao Cui, Ying Song, Shuguang Wu, Kai Sun, Weidong Xiao, Tangfu |
| Affiliation | Guangzhou Univ, Sch Environm Sci & Engn, Key Lab Water Qual & Conservat Pearl River Delta, Minist Educ, Guangzhou 510006, Peoples R China Peking Univ, Sch Earth & Space Sci, MOE Key Lab Orogen Belts & Crustal Evolut, Beijing, Peoples R China Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian, Peoples R China Chinese Acad Sci, Ctr Deep Sea Res, Inst Oceanol, Qingdao, Peoples R China Pilot Natl Lab Marine Sci & Technol Qingdao, Lab Marine Mineral Resources, Qingdao, Peoples R China |
| Keywords | CONTINENTAL-CRUST NW CHINA SUBDUCTION INITIATION ARC MAGMATISM ZIRCON EVOLUTION ROCKS BLOCK BELT GENERATION |
| Issue Date | Apr-2020 |
| Publisher | INTERNATIONAL GEOLOGY REVIEW |
| Abstract | Granitoids in active continental margins are probes of sub-arc magmatic processes and are crucial for the understanding of crust-mantle interaction during subduction. Here we report data for the middle to late Cambrian Tuole (TL) and Dabaishitou (DBST) granitic plutons in the western segment of the North Qilian suture zone (NQSZ). The TL-DBST plutons comprise monzonite, alkali-feldspar granite, gabbroic diorite, monzonitic porphyry and biotite monzogranite. Zircon U-Pb ages reveal that these granitoids crystallized at ca. 509-492 Ma, consistent with the early subduction of the North Qilian Ocean. Mineralogical, petrological, and geochemical features indicate that the TL monzonite and gabbroic diorite are both high-K calc-alkaline I-type granitoids but the latter is Nb-enriched; the TL alkali-feldspar granites and DBST granitoids belong to aluminous A-type and transitional I- and A-type granites, respectively. The I- and aluminous A-type granites show similar and comparable isotopic compositions, e.g., epsilon(Hf)(t) values of -5.6 to +2.7 versus -2.4 to +3.5, but different melting conditions, e.g., high temperature and low oxygen fugacity for aluminous A-type granites as indicated by zircon trace elements. Geochemical and isotope data suggest that all these granitoids were mainly derived from the sub-arc mantle metasomatized by slab-derived fluids/asthenospheric mantle-derived melts/both prior to melting with minor input of LCC-derived melts (ca. 10-20%). The HFSE enrichment feature was inherited by granites and further enhanced by protracted crystal fractionation at low oxygen fugacity conditions to produce the TL aluminous A(1)-type granites but weakened by fractionation at relatively high oxygen fugacity conditions to produce the DBST I-A-transitional-type granite. Partial melting of the sub-arc lithospheric mantle was induced by upwelling of the asthenospheric mantle and their interactions in response to slab rollback during subduction initiation (ca. 509-506 Ma), and by addition of slab-derived fluids again as subduction proceeded (ca. 493-492 Ma). |
| URI | http://hdl.handle.net/20.500.11897/606668 |
| ISSN | 0020-6814 |
| DOI | 10.1080/00206814.2020.1746931 |
| Indexed | SCI(E) Scopus |
| Appears in Collections: | 地球与空间科学学院 造山带与地壳演化教育部重点实验室 |
