caa a22 4500 445301007 CHVBK 20180317142557.0 cr unu---uuuuu 170323e20100201xx s 000 0 eng 10.1007/s11430-009-0100-5 doi (NATIONALLICENCE)springer-10.1007/s11430-009-0100-5 Zircon U-Pb dating and geochemical study of the Xianggou granite in the Ma'anqiao gold deposit and its relationship with gold mineralization [Elektronische Daten] [LaiMin Zhu, GuoWei Zhang, Ben Lee, Bo Guo, HuJun Gong, Lei Kang, ShiLing Lü] Single zircon LA-ICP-MS U-Pb dating and lithogeochemical studies have been performed on the Xianggou monzonitic granitic porphyry outcropped in the Ma'anqiao gold deposit. A weighted average U-Pb age of 242.0±0.8 Ma for Xianggou monzonitic porphyry has been obtained. This corresponds with the conclusions of previous studies indicating a syn-orogenic age (242±21 Ma) of the Qinling Orogenic Belt, suggesting that the formation of the Xianggou granite should be associated with the collisional event of the North China Plate and the Yangtze Plate in the Indosinian period. The Xianggou granite is characterized by the high silicon and alkali of high K calc-alkaline series granites. It is rich in Al (Al2O3=14.49%−15.61%) and Sr (457.10-630.82 ppm), poor in Y (<16 ppm) and HREE (Yb<0.45 ppm), and exhibits high ratios of Sr/Y (76.24-97.34) and (La/Yb)N (29.65-46.10), as well as strongly fractionated REE patterns. These geochemical characteristics suggest the Xianggou granite can be classified as C-type adakitic rock. The initial Sr isotope ratios for the Xianggou granite vary from 0.70642 to 0.70668, ɛ Nd(t) values from −4.54 to −3.98, and T DM values from 1152 Ma to 1220 Ma. The low ɛ Nd(t) and I Sr and high T DM values, as well as Na2O/K2O ratios of the Xianggou granite are close to 1 (Na2O/K2O=0.95−1.10), indicating that it is not an I-type adakite formed by partial melting of the subducting oceanic crust, nor adakitic rock formed by melting of the underplated basaltic lower crust, but the product of partial melting of the nonunderplated basaltic thickened lower crust. Zircons from the Xianggou pluton have a homogeneous Hf isotopic composition with negative ɛ Hf(t) values (between −9.7 and −5.9, with an average of −6.9), indicating that the rock-forming materials were mostly extracted from the ancient crust, not from the depleted mantle. The Xianggou monzonitic granitic porphyry is rich in LILE and LREE and depleted in HSFE, HREE and Y; the composition of trace element and REE are similar to those of the syn-collisional granites. The geological and geochemical characteristics of the Xianggou granite reveal that it was a product of partial melting of the basaltic rocks from the thickened lower crust, triggered by continental collision, which occurred in the geodynamic background of continental-continental collision and shearing within the crust. The Xianggou granite was intruded in the compressive orogenic environment 242 Ma ago, but the gold mineralization occurred in the transitional environment of compression to extension around 170 Ma ago, lagging behind the intrusive age of the Xianggou granite by about 70 Ma. Meanwhile, the distribution of trace elements and REEs of the Xianggou monzonitic granitic porphyry is distinct from that of ores, suggesting the absence of direct genetic relationship between the Xianggou granite and gold mineralization. In contrast, the relatively high ore-forming elemental content of the Xianggou monzonitic granitic porphyry is due to the rock having experienced Au-bearing hydrothermal alteration. From the view of gold mineralization, considering the intrusive age, structural deformation, as well as alteration of the granite, we can conclude that the Xianggou pluton was a pre-ore-intrusion, whose intrusive age of 242 Ma constrains the lower time limit of gold metallogenesis. Following the intrusive event of the syn-collisional granitic porphyry and the intensively brittle-ductile shear deformation, large-scale fluid activity and gold mineralization took place. Science in China Press and Springer Berlin Heidelberg, 2010 zircon U-Pb dating nationallicence Xianggou monzonitic granitic porphyry nationallicence Carlin type and Carlin-like type gold deposits nationallicence petrologenic and metallogenic dynamic background nationallicence Zhu LaiMin State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Zhang GuoWei State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Lee Ben State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Guo Bo State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Gong HuJun State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Kang Lei State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Lü ShiLing State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut Science China Earth Sciences SP Science in China Press 53/2(2010-02-01), 220-240 1674-7313 53:2<220 2010 53 11430 https://doi.org/10.1007/s11430-009-0100-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11430-009-0100-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Zhu LaiMin State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 700 1- Zhang GuoWei State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 700 1- Lee Ben State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 700 1- Guo Bo State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 700 1- Gong HuJun State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 700 1- Kang Lei State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 700 1- Lü ShiLing State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China aut NATIONALLICENCE 773 0- Science China Earth Sciences SP Science in China Press 53/2(2010-02-01), 220-240 1674-7313 53:2<220 2010 53 11430 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer