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SHRIMP U-Pb zircon geochronology of granulites at Rimana(Southern Tibet)in the central segment of Himalayan Orogen [查看] LIDewei、LIAOQunan、YUANYanming、WANYusheng、LIUDemin、ZHANGXionghua、YIShunhua1、CAOShuzhao、XIEDefan

Abstract High-pressure mafic granulites, occurring as lenses within gneisses and quartzite in the central segment of the Himalayan orogen, were dated using SHRIMP U-Pb technique. 13 analyses out of a total of 15 are plotted along a concordia line and yield a mean 206Pb/238U age of 17.6 ± 0.3Ma. This age indicates adiabatic decompression and a metamorphic event associated with rapid uplift of granulites in a tectonic environment resulted from the collision between India and Eurasia, synchronous with large-scale thrusting, extension, detachment as well as emplacement of leucogranite.One analysis gives a 206Pb/238U age of 29.5 ± 0.4 Ma that is interpreted to represent the timing of the final closure of the Neo-Tethys. Another age is 1991 ± 26 Ma that represents the age of the protolith of the granulites. In summary,dating results show that granulites in this area underwent multiphase metamorphism and complex geological evolution.

Mineralizing age of the Rushan lode gold deposit in the Jiaodong PeninsulaSHRIMP U-Pb dating on hydrothermal zircon [查看] HUFangfang、FANHongrui、YANGJinhui、WANYusheng、LIUDunyi、ZHAIMingguo、JINChengwei

Abstract Zircons from the auriferous quartz vein in the Rushan gold deposit, Jiaodong Peninsula, have high common Pb contents (206Pbc = 2.00%—15.88%) and Th/U ratios (0.31—1.35), and trap primary CO2-H2O fluid inclusion similar to ore-forming fluids, indicating that they grew from high Th/U ratio ore-forming fluids responsible for gold mineralization.SHRIMP U-Pb analyses of these zircons gave an age of 117±3 Ma comparable with the ages reported by the former researches in the other areas in the Jiaodong Peninsula, which is interpreted as the age of gold mineralization at Rushan. The age of SHRIMP zircon U-Pb dating with 160±3 Ma from host rock Kunyushan monzogranite is different from that of the gold mineralization, indicating that there is no genetic relationship between gold mineralization and the granitic magmatism. SHRIMP U-Pb dating on hydrothermal zircons from auriferous quartz veins could be used to constrain the timing of lode gold mineralization and the relationship to relevant hydrothermal event.

The Dabie Orogen as the early Jurassic sedimentray provenanceConstraints from the detrital zircon SHRIMP U-Pb dating [查看] LIRenwei、WANYusheng、CHENGZhenyu、ZHOUJianxiong、XUYunhua、LIZhong、JIANGMaosheng

Abstract The SHRIMP U-Pb ages of detrital zircon from the oldest Mesozoic strata, the Fanghushan Fomation, in the Hefei Basin range from 200 Ma to ca. 2500 Ma, which indicates that the Dabie Orogen as the early Jurassic sedimentary provenance was complex. The composition of the Dabie Orogen includes: the Triassic high pressure-ultrahigh pressure metamorphic rocks, of which the detrital zircon ages are from 234 Ma to 200 Ma; the rocks possibly related to the Qinling and Erlangping Groups representing the southern margin of the Sino-Korean craton in the Qinling and Dabie area, of which the detrital zircon has an age of 481±378 Ma; the Neoproterozoic rocks originated from the Yangtze croton, of which the detrital zircon ages are 799±721 Ma old; and the rocks with the detrital zircon ages of ca. 2000 Ma and ca. 2500 Ma, which could be the old basement of the Yangtze craton.

The age of the base of the Paleoproterozoic Hutuo Group in the Wutai Mountains area, North China Craton SHRIMP zircon U-Pb dating of basaltic andesite [查看] DULiLin、YANGChongHui、GUOJingHui、WANGWei、RENLiuDong、WANYuSheng、GENGYuanSheng

Basalt and basaltic andesite metamorphosed at greenschist facies occurs with conglomerate layers at the bottom of the Paleoproterozoic Hutuo Group in the Wutai Mountains area, North China Craton. Detailed geological surveying confirms that these volcanic rocks are conformable within the neighboring sedimentary rocks. The SHRIMP results on basaltic andesite are divided into two groups. In one group the 207Pb/206Pb ages are from 2433 to 2558 Ma, which is consistent with the basement crustal age in Fuping and Wutai areas. In the other group, 13 grains yielded a weighted mean 207Pb/206Pb age of 2140±14 Ma. The latter is interpreted as the eruption age of the basaltic andesite, and gives the age of the base of the Hutuo Group. This result further suggests that the Hutuo Group formed in the middle Paleoproterozoic, not the early Palaeoproterozoic or late Archaean, as thought before,and is related to a 2.2−2.1 Ga rifting event in the Central North China Craton.

SHRIMP U-Pb dating for a K-bentonite bed in the Tieling Formation,North China [查看] SUWenBo、LIHuaiKun、HUFFWD、ETTENSOHNFR、ZHANGShiHong、ZHOUHongYing、WANYuSheng

A SHRIMP U-Pb zircon age of 1437±21 Ma was obtained for a recently discovered K-bentonite bed in the Tieling Formation,situated northeast of Beijing at the boundary between Liaoning and Hebei provinces, on the northern margin of the North China Craton (NCC). The SHRIMP U-Pb age places Tieling Formation near the end of the Calymmian Period of the early Mesoproterozoic Era. In addition, a SHRIMP U-Pb zircon date of 1372±18 Ma was acquired for K-bentonite beds in the overlying,dark-shale-dominated Xiamaling Formation from the same location northeast of Beijing. This date assigns a similar Mid-Mesoproterozoic (Ectasian Period) age for the Xiamaling Formation, as have previously determined dates from other sections northwest of Beijing. These dates indicate that the Tieling and Xiamaling formations, as well as the related succession in the eastern part of the Yanshan Mountains, represented by the well-known Meso- to Neoproterozoic standard section in Jixian, can be correlated well with sections northwest of Beijing in the western part of the Yanshan Mountains. In other words, the boundary between the Calymmian and Ectasian periods in the northern parts of the NCC is marked by the unconformity between the Tieling and Xiamaling formations in the northern NCC. This boundary was previously ascribed to the “Qinyu Orogeny” and thought to be of Grenville age. In this regard, the conventional “Qinyu Orogeny” should now be regarded as a short-lived regional uplift during Early Mesoproterozoic time, rather than a result from the Grenvillian assembly of the NCC to the Rodinia Supercontinent (~1.0 Ga).

Report on 3.4 Ga SHRIMP Zircon Age from the Yuntaishan Geopark in Jiaozuo, Henan Province [查看] GAOLinzhi、ZHAOTing、WANYusheng、ZHAOXun、MAYinsheng、YANGShouzheng

Using the reported new U-Pb age with the Sensitive High-Resolution Ion hlicroprobe (SHRIRIP-II), zircon U-Pb ages were obtained from two samples of K-feldspar felsic paragneiss and K-feldspar gneissoid trondhjemite on the southern margin of the Taihang hlountains in the North China Craton. The protolith of the K-feldspar felsic paragneiss is argillaceous-sandy clastic sedimentary rock, probably deposited in the Neoarchean. Most of the detritus zircons show heavy loss of Pb. Five spots of zircons near the upper point, yield a weighted mean 207Pb/206Pb age of 3399±8 Ma, representing an age of the sedimentary source. Two groups of zircons from the K-feldspar gneissoid trondhjemite give weighted mean 207Pb/206Pb ages of 2511±13 Ma and 2735±16 Ma respectively. The former represents the emplacement time of the pluton, while the latter is interpreted as the age of the inherited zircons. The new data support that the Archean geological body in the central zone has an affinity with those from the eastern block of the North China Craton.

SHRIMP zircon U-Pb dating for subduction-related granitic rocks in the northern part of east Junggar, Xinjiang [查看] ZHANGZhaochong、YANShenghao、CHENBailin、ZHOUGang、HEYongkang、CHAIFengmei、HELixin、WANYusheng

SHRIMP U-Pb zircon dating on the Xileketehalasu granodiorite porphyry and Kalasayi monodiorite porphyry that intrude middle Devonian Beitashan Formation at the north part of east Junggar region shows that they were formed at 381±6 Ma and 376±10 Ma respectively. They are interpreted as subduction-related granitic rocks, which is the first report that the isotopic ages for the granitic rocks range from 350 to 390 Ma. Another determined age for the Kalasayi monodiorite porphyry is 408±9 Ma,representing the age of underlain Lower Devonian volcanic rocks. Thus, the U-Pb dates suggest that the northeastward subduction of Junggar ocean from southwest occurred at 408 to 376 Ma (the real inter-val may be larger). Because the ore bearing porphyry intruded following the formation of the volcanic rocks of middle Devonian Beitashan Formation, their tec-tonic setting is similar to the Andes Mountains that hosts world-class porphyry copper deposits, and the researched area could be regarded as a potential area for prospecting large porphyry copper deposits.

Polyphase tectonothermal history recorded in granulitized gneisses from the North Qaidam HPUHP metamorphic terrane,Western Chinaevidence from zircon U-Pb geochronology [查看] ZhangJianxin、ChristopherG.Mattinson、MengFancong、WanYusheng、Dongkuoan

Finding of Neoproterozoic (~775 Ma) magmatism recorded in metamorphic complexes from the North Qilian orogen Evidence from SHRIMP zircon U-Pb dating [查看] Chien-YuanTseng、Houng-YiYang、WANYusheng、LIUDunyi、Da-JenWen、Tzung-ChiLin、Kuo-AnTung

SHRIMP U-Pb dating was carried out on zircons from the Niuxinshan gneissic granite and the Leigongshan gneissic tonalite in the North Qilian orogen, NW China. The results yield weighted aver-aged 206Pb/238U ages of 776±10 Ma and 774±23 Ma respectively. Igneous morphology, oscillatory zonings, and relatively high Th/U ratios for these zircons suggest magmatic origin. These ages are interpreted as timing of magma emplacement and thus repre-senting a Neoproterozoic (~775 Ma) magmatic event in the North Qilian area. It is suggested that this magmatism is probably related to breakup of the supercontinent Rodinia. This finding, together with the similar ages of 750 to 800 Ma reported for neighboring terranes of South-central Qilian and North Qaidam, is of significance to understanding of the Rodinia evolution in West China.

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