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Timing of Palaeoproterozoic crustal shearing in the central Fennoscandian Shield according to U-Pb data from associated granitoids, Finland  [PDF]
Matti Vaasjoki,Aulis K?rki,Kauko Laajoki
Bulletin of the Geological Society of Finland , 2001,
Abstract: Granitoids in the Finnish part of the Fennoscandian Shield were created by numerous Archaean and Palaeoproterozoic tectonic events. Late phases of Palaeoproterozoic, Svecokarelian deformation created ductile, crustal-scale shear zones, of which the N-S striking Hirvaskoski Shear Zone and the NE-SW striking Ouluj rvi Shear Zone were strongly affected by the latest deformation stages, D3 and D4. These shear tectonic events deformed ductilely prekinematic granitoids and caused intrusion of synkinematic igneous rocks, but the D3 and D4 fault rocks are also penetrated by postkinematic intrusives.Archaean granitoids behaved mostly as rigid blocks unaffected by Palaeoproterozoic deformation. However, inherited Archaean zircons occur in some obviously Proterozoic granitoids, and others contain heterogeneous zircon populations. Granitoids lacking structures of the earliest deformations, D1 and D2, contain inherited zircon populations partially reset during the Svecokarelian orogeny and have been sheared ductilely during stages D3 and D4. Granitic rocksyielding zircon ages of 1.82-1.80 Ga show no features associated with these shearing events and penetrate the D4 fault rocks setting a minimum age for these deformation events. This age marks also the end of convergent tectonics in the central Fennoscandian Shield. Monazite data from a variety of rocks demonstrates a regional cooling below the 600°C isotherm at 1.8 Ga.
The first discovery of eclogite and Palaeoproterozoic granitoids in the Beishan area, northwestern Gansu Province, China
Hualin Mei,Haifeng Yu,Quan Li,Songnian Lu,Huimin Li,Yicheng Zuo,Guochao Zuo,Dejin Ye,Jincheng Liu
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02885491
Abstract: The eclogite, discovered in Liuyuan, occurs as lenticular enclave within granitic gneiss. It has typical features of eclogite in petrology and mineralogy. The eclogite provides an important window to reconstruct the tectonic border of the Tarim block. The granitoids, located in Baihu area, yield U-Pb zircon ages of 1 660–2 000 Ma (Palaeoproterozoic), which implies an early Precambrian basement in the area.
The first discovery of eclogite and Palaeoproterozoic granitoids in the Beishan area, northwestern Gansu Province, China

Hualin Mei,Haifeng Yu,Quan Li,Songnian Lu,Huimin Li,Yicheng Zuo,Guochao Zuo,Dejin Ye,Jincheng Liu,

科学通报(英文版) , 1999,
Abstract: The eclogite, discovered in Liuyuan, occurs as lenticular enclave within granitic gneiss. It has typical features of eclogite in petrology and mineralogy. The eclogite provides an important window to reconstruct the tectonic border of the Tarim block. The granitoids, located in Baihu area, yield U-Pb zircon ages of 1 660–2 000 Ma (Palaeoproterozoic), which implies an early Precambrian basement in the area.
Geochemistry and petrogenesis of Jurassic high Sr/low Y granitoids in eastern China: Constrains on crustal thickness
Xiaoyue Ge,Xianhua Li,Zhigang Chen,Wuping Li
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9216
Abstract: The Jurassic high Sr/low Y granitoids in eastern China are characterized by high Sr/Y (27–166) and La/Yb (14–66) ratios, low abundance in Y (6–21 μg/g) and Yb (0.5-2.0 μg/g), comparable with those of adakites defined by Defant et al. Thus, they were recently considered as adakitic rocks by some researchers. Compared with the typical adakites in circum-Pacific margins, however, these high Sr/low Y granitoids have higher K2O ( 3.5%) but lower Al2O3 ( 16.0%) as well as lower Mg# ( 38) and δSrn ( 1.23) values. Furthermore, they show relatively flat HREE patterns with Y/Yb values of 10 close to the chondritic value. These geochemical characteristics indicate a residue mineral assemblage of hornblende, garnet and plagioclase for these high Sr/low Y granitoids melt. Thus, they were generated by partial melting at 9–13 kbar (30–45 km in depth), similar to the Archaean high-Al TTG rather than the modern adakites. Generation of these high Sr/low Y granitoids cannot be considered as evidence for a thickened crust (>50 km) and/or the presence of the “Eastern China Plateau” in Jurassic.
Geochemistry and petrogene-sis of Jurassic high Sr/low Y granitoids in eastern China:Constrains on crustal thick-ness

GE Xiaoyue,LI Xianhua,CHEN Zhigang,LI Wuping,

科学通报(英文版) , 2002,
Abstract: The Jurassic high Sr/low Y granitoids in eastern China are characterized by high Sr/Y (27-166) and La/Yb (14-66) ratios, low abundance in Y (6-21 μg/g) and Yb (0.5-2.0 μg/g), comparable with those of adakites defined by Defant et al. Thus, they were recently considered as adakitic rocks by some researchers. Compared with the typical adakites in circum-Pacific margins, however, these high Sr/low Y granitoids have higher K2O (-3.5%) but lower Al2O3 (-16.0%) as well as lower Mg# (-38) and δ SrN (-1.23) values. Furthermore, they show relatively flat HREE patterns with Y/Yb values of ?10 close to the chondritic value. These geochemical characteristics indicate a residue mineral assemblage of hornblende, garnet and plagioclase for these high Sr/low Y granitoids melt. Thus, they were generated by partial melting at 9-13 kbar (30-45 km in depth), similar to the Archaean high-Al TTG rather than the modern adakites. Generation of these high Sr/low Y granitoids cannot be considered as evidence for a thickened crust (>50 km) and/or the presence of the "Eastern China Plateau" in Jurassic.
SHRIMP zircon U-Pb dating of the Gangou granitoids, Central Tianshan Mountains, Northwest China and tectonic significances
YuRuo Shi,DunYi Liu,Qi Zhang,Ping Jian,FuQin Zhang,LaiCheng Miao
Chinese Science Bulletin , 2007, DOI: 10.1007/s11434-007-0204-2
Abstract: Two types of granitoids, highly deformed augen granitoids and undeformed fine-grained granitoids, are widely distributed in Gangou area, Central Tianshan Mountains, Northwest China. The augen granitoids are high-K calc-alkaline characterized by high K2O, Rb, Y and Th, and low Sr and Sr/Y. They also have high contents of large ion lithophile elements (LILE), such as Ba, Rb, K and Th, and relatively low contents of high field strength elements (HFSE), such as Zr, Y and Nb. The fine-grained granitoids are calc-alkaline characterized by high Sr, low Y and HREE, similar to adakitic rocks, and with Na2O/K2O<2 (1.76–1.91), high I Sr (0.70689–0.70981), and negative ε Nd(t) ( 2.4– 5.3). High-precision SHRIMP U-Pb zircon dating results indicate that the Gangou augen granitiods were formed at 428 ±10 Ma, and the fine-grained granitoids were emplaced at 361–368 Ma. These geochemical and U-Pb zircon data have significant implications for the timing of closure of the Mishigou-Gangou Ocean and the evolution of the Central Tianshan orogenic belt.
STUDY ON THE TYPOMORPHIC CHARACTERISTICS OF ZIRCON FROM TWO DIFFERENT TYPES OF MINERALIZED GRANITOIDS OF YANSHAN OROGENY IN SOUTH CHINA
华南燕山期两种不同矿化花岗岩类中锆石标型特征的研究

Gao Shanji Gao Yanjun Zhai Liua Ying Lan,
高善继
,高艳君,翟丽娜,应兰

岩石学报 , 1987,
Abstract: This paper deals in details with zircon mineralogy of two different types of mineralized granitoids (REE, RE tungstentin mineralized granitoid and copper, polymetal mineralized granitoid from eight rock masses with 30 artificial heavy concentrate samples in total) including physical properties of minerals, x-ray powder analysis,chemical analysis, infrared spectrometry and ESM etc. First,the geological occurrence and paragenious minerals of zircon in granitoids of two types of mineralization are discussed. Then the typomorphic characteristics of zircon from two different types of mineralized granitoids of Yanshang orogeny in South China are summed up on the basis of systematic sorting out and all-sided analysis of numerous test data. The results of investigatiions show that the zircon typomorphic characteristics of the above-mentioned two types of mineralized granitoids remarkably differ from each other. The significance of the two types of zircon typomorphic characteristics is emphasized in this paper. Furthermore, the controlling factors and formation mechanism of the zircon typomorphic characteristics are discussed. On this basis, some ore-prospecsing criteria in the diversed mineralized granitoids of Yanshang orogeny in South China are pointed out.
Formation ages and source regions of the Palaeoproterozoic Gaofan, Hutuo and Dongjiao groups in the Wutai and Dongjiao areas of the North China Craton from SHRIMP U-Pb dating of detrital zircons: Resolution of debates over their stratigraphic relationships
YuSheng Wan,PeiSheng Miao,DunYi Liu,ChongHui Yang,Wei Wang,HuiChu Wang,ZheJiu Wang,ChunYan Dong,LiLin Du,HongYing Zhou
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-009-0615-3
Abstract: This paper reports detrital zircon age distributions of meta-sedimentary rocks of the Gaofan, Hutuo and Dongjiao groups in the Wutai and Dongjiao areas of the North China Craton. Detrital zircons of a quartzite from the Gaofan Group are mainly ~2.5 Ga in age, with some ~2.7 Ga and older. A quartzite pebble from the basal conglomerate of the Hutuo Group is similar in detrital zircon age distribution to the quartzite of the Gaofan Group. For a meta-feldspar-quartz sandstone from the Dongjiao Group, the age of detrital zircons is mainly concentrated at ~2.5 Ga. No zircons older than 2.6 Ga have been identified, but with some being 1.84 Ga and 2.2–2.0 Ga in age. Combined with earlier studies, the following conclusions can be drawn: (1) The Gaofan Group is early Palaeoproterozoic in age and is much younger and unrelated to the late Neoarchaean Wutai granite-greenstone terrane, which it unconformably overlies. As such, the Gaofan Group is one of the oldest Palaeoproterozoic meta-sedimentary units in the North China Craton. (2) The Hutuo Group was deposited in the middle Palaeoproterozoic (2.14-2.09 Ga) on a continental basement, after the early Palaeoproterozoic Gaofan Group. (3) The Dongjiao Group was formed after 1.84 Ga, and probably belongs to the lower portion of the Changcheng System. (4) The detrital zircons from all the three groups show an obvious age peak of ~2.5 Ga, being sourced from the igneous rocks formed in the intense tectono-magma-thermal events at the end of Archaean in the North China Craton.
SHRIMP zircon U-Pb dating of the Gangou granitoids, Central Tianshan Mountains, Northwest China and tectonic significances
Shi Yuruo,Liu Dunyi,Zhang Qi,Jian Ping,Zhang Fuqin,Miao Laicheng,
SHI
,YuRuo,LIU,DunYi,ZHANG,Qi,JIAN,Ping,ZHANG,FuQin,MIAO,LaiCheng

科学通报(英文版) , 2007,
Abstract: Two types of granitoids, highly deformed augen granitoids and undeformed fine-grained granitoids, are widely distributed in Gangou area, Central Tianshan Mountains, Northwest China. The augen granitoids are high-K calc-alkaline characterized by high K2O, Rb, Y and Th, and low Sr and Sr/Y. They also have high contents of large ion lithophile elements (LILE), such as Ba, Rb, K and Th, and relatively low contents of high field strength elements (HFSE), such as Zr, Y and Nb. The fine-grained granitoids are calc-alkaline characterized by high Sr, low Y and HREE, similar to adakitic rocks, and with Na2O/K2O<2 (1.76–1.91), high I Sr (0.70689–0.70981), and negative ε Nd(t) ( 2.4– 5.3). High-precision SHRIMP U-Pb zircon dating results indicate that the Gangou augen granitiods were formed at 428 ±10 Ma, and the fine-grained granitoids were emplaced at 361–368 Ma. These geochemical and U-Pb zircon data have significant implications for the timing of closure of the Mishigou-Gangou Ocean and the evolution of the Central Tianshan orogenic belt. Supported by the National Natural Science Foundation of China (Grant Nos. 40234045 and 40473030)
Timing of late Palaeoproterozoic metamorphism in the northern Belomorian Belt, White Sea region: conclusions from U-Pb isotopic data and P-T evidence  [PDF]
Torbj?rn Ski?ld,Svetlana Bogdanova,Roland Gorbatschev,Elena Bibikova
Bulletin of the Geological Society of Finland , 2001,
Abstract: Brilliant-looking zircon crystals from a garnet-amphibolitic, metamorphosed mafic dyke at Lyagkomina in the Lake Kovdozero area, northern Belomorian Belt, most probably mark the 1875±4 Ma age of peak late Palaeoproterozoic regional metamorphism which followed upon dyke intrusion associated with deformation of the Lapland-Kola orogenic tectonic collage. U-Pb ages of titanites (ca. 1860 Ma) and rutiles (ca. 1750 Ma) help reconstruct the retrograde path and the cooling rates which decreased with time. The new titanite and rutile ages agree well with similar age data previously obtained on a regional scale from the central part of the belt and suggest absence of variation in mineral ages as a function of lithological differences. P-T analysis of the metamorphic parageneses indicates initial sharp decompression after peak metamorphism and jump uplift with unroofing of ca. 9-10 km of the crust in the Belomorian Belt previously thickened by late Palaeoproterozoic orogenic thrusting and stacking.
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