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1.
Qin Zhou Qing-Zhu Yin Charles K. Shearer Xian-Hua Li Qiu-Li Li Yu Liu Guo-Qiang Tang Chun-Lai Li 《Meteoritics & planetary science》2018,53(3):448-466
The Antarctic achondrite Graves Nunataks 06128 (GRA 06128) and Graves Nunataks 06129 (GRA 06129) represent a unique high-temperature, nonbasaltic magmatism in the early solar system. These objects have been interpreted as products of low-degree partial melting of volatile-rich chondritic material, which may have been the asteroid parent bodies of brachinite. Previous studies have investigated their crystallization and metamorphic history with various isotope systematics. Here, we report the U-Pb intercept age of 4466 ± 29 Ma and the weighted-average 207Pb-206Pb age of 4460 ± 30 Ma for the Cl-apatite grains from GRA 06129. Our apatite ages are obviously younger than that of the 26Al-26Mg model age (4565.9 ± 0.3 Ma; Shearer et al. 2010a ), but are the same as the 40Ar-39Ar age obtained via step-heating of the bulk rock (4460 ± 28 Ma; Fernandes and Shearer 2010 ; Shearer et al. 2010a ). Based on petrographic observations, merrillites are usually rimmed by apatite and exist as inclusions in apatite. Therefore, the apatite U-Pb age from GRA 06129 probably records a metamorphic event of replacing merrillite with apatite, caused by Cl-rich melts or fluids on their parent body. A collisional event has provided the impact heating for this metamorphic event. Increasing amounts of geochronologic evidence show that the giant impact of the Moon-forming event has affected the asteroid belt at 4450–4470 Ma (Bogard and Garrison 2009 ; Popova et al. 2013 ; Yin et al. 2014 ; Zhang et al. 2016 ). Considering the contemporary metamorphic events for GRA 06129 (4460 ± 30 Ma), it is likely that the asteroid parent body of GRA 06129 was also affected by the same giant impact as the Moon-forming event. 相似文献
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Mineralogy and Petrology - The geochemical and isotopic investigations were provided on the Upper Eocene Senj mafic intrusion and Mo-Cu mineralization to better understand the tectono-magmatic... 相似文献
3.
In the Variscan French Massif Central and Armorican Massif, the tectonic significance of a widespread NW–SE-trending stretching lineation, coeval with medium pressure–medium temperature metamorphism, is an open question. Based on a structural analysis in the southern part of the Massif Central, we show that this top-to-the-NW shearing is a deformation event, referred to as D2, which followed a D1 top-to-the-south shearing Devonian phase, and was itself re-deformed by a Late D3 Visean–Serpukhovian southward-thrusting event. We date the D2 phase at 360 Ma (Famennian–Tournaisian boundary). In the Armorican Massif, D2 is the “Bretonian phase” recorded in the metamorphic series and sedimentary basins. Geodynamically, D2 is related to a general northwestward shearing during the Laurussia–Gondwana collision, which occurred after the closure of the Rheic Ocean, as indicated by the emplacement of the Lizard ophiolitic nappe in Britain. The left-lateral Nort-sur-Erdre fault accommodated the absence of ductile shearing in Central Armorica. 相似文献
4.
An early Paleoproterozoic high-K intrusive complex in southwestern Tarim Block, NW China: Age, geochemistry, and tectonic implications 总被引：7，自引：2，他引：7
Chuan-Lin Zhang Zheng-Xiang Li Xian-Hua Li Hai-Feng Yu Hai-Ming Ye 《Gondwana Research》2007,12(1-2):101
Systematic geochronologic, geochemical, and Nd isotopic analyses were carried out for an early Paleoproterozoic high-K intrusive complex exposed in southwestern Tarim, NW China. The results provide a better understanding of the Paleoproterozoic tectonic evolution of the Tarim Block. Zircon U–Pb age dating indicates two Paleoproterozoic magmatic episodes occurring at ca. 2.41 Ga and ca. 2.34 Ga respectively, which were followed by a ca. 1.9 Ga metamorphic event. The 2.41 Ga granodiorite–adamellite suite shares characteristics of late to post-orogenic metaluminous A-type granites in its high alkalinity (Na2O + K2O = 7.6–9.3%), total REE (410–788 ppm), Zr (370–660 ppm), and Y (21.7–58.4 ppm) contents. εNd(t) values for the suite range from − 3.22 to − 4.71 and accordingly the Nd modal ages (T2DM) vary between 3.05 Ga and 3.17 Ga. Based on geochemical data, the 2.34 Ga suite can be subdivided into two sub-suites, namely A-type and S-type. However, both types have comparable Nd isotope compositions (εNd(t) ≈ − 0.41 to − 2.08) and similar narrow T2DM ranges (2.76–2.91 Ga).Geochemical and Nd isotopic data for the high-K intrusive complex, in conjunction with the regional geological setting, suggest that both the 2.41 Ga suite and the 2.34 Ga A-type sub-suite might have been produced by partial melting of the Archean mafic crust in a continental rift environment. The S-type sub-suite is thought to have formed by partial melting of felsic pelites and/or metagreywackes recycled from Archean crust (TTG?). Gabbro enclaves with positive εNd(t) value (2.15) have been found to be intermingling within the 2.34 Ga suite; ca. 2.34–2.36 Ga gabbroic dykes and adamellites have previously been documented in eastern Tarim. These observations indicate that the high-K intrusions may reflect the emergence of depleted mantle upwelling beneath the Tarim Block at that time. We suggest a three-stages model for the Precambrian crustal evolution in the Tarim Block: (1) the formation of proto-crust (TTG) by ca. 2.5 Ga, (2) episodes of felsic magmatism possibly occurring in continental rift environments at ca. 2.41 Ga and ca. 2.34–2.36 Ga, and (3) ca. 1.9 Ga metamorphism that may represent the solidification of the Precambrian basement of the Tarim Block. 相似文献
5.
Hong-Fu Zhang Ji-Feng Ying Yan-Jie Tang Xian-Hua Li Chuang Feng M. Santosh 《Gondwana Research》2011,19(2):446-459
The Archean lithospheric root of the North China Craton (NCC) has been considerably eroded and modified by Phanerozoic magmatic processes. Here we investigate the decratonization of the NCC through U–Pb and Hf isotopic analyses of zircons from Cenozoic basalts in the Liaodong Peninsula using ion-probe and MC-ICPMS techniques. The U–Pb zircon geochronology identifies three zircon populations: Precambrian, Paleozoic and Mesozoic. The Precambrian zircons yield 207Pb/206Pb ages of 2275–2567 Ma with a peak at around 2.5 Ga. They define a U–Pb discordia with upper intercept ages of 2447 ± 50 Ma to 2556 ± 50 Ma and a wide range of Hf TDM ages with a mode at 2.7–2.8 Ga. Our results clearly demonstrate the presence of an Archean lower crust in the Liaodong region. The Paleozoic zircons from the Liaodong region lack the clear internal zoning and are subhedral to rounded in shape, and yield a narrow 206Pb/238U concordant ages of 419–487 Ma with a weighted mean age of 462 ± 16 Ma. The Mesozoic zircons predominantly show crystallization in the early Cretaceous and yield a relatively large range in 206Pb/238U ages from 100 to 138 Ma (n = 53) with a peak around 120 Ma. Three samples give indistinguishable weighted mean 206Pb/238U ages of 120 ± 5 Ma, 120 ± 4 Ma and 121 ± 2 Ma. These early Cretaceous zircons have enriched Hf isotope compositions with εHf(t) values from ?26 to ?16. Our results provide important constraints on episodic magmatism during the Phanerozoic in the Liaodong region, which led to substantial reactivation of the Archean basement of the North China Craton. 相似文献
6.
Qiu-Li Li Xian-Hua Li Yu Liu Fu-Yuan Wu Jin-Hui Yang R.H. Mitchell 《Chemical Geology》2010,269(3-4):396-405
Perovskite, a common Th- and U-enriched accessory mineral crystallised from kimberlitic magmas, has long been thought to be an important geochronometer for dating the emplacement of kimberlite. However, it also contains variably high levels of common Pb, which makes it difficult to obtain a precise measurement of radiogenic Pb/U and Pb/Th isotopic compositions using microbeam techniques such as SIMS and LA-ICP-MS. We present calibration protocols for in situ U–Pb and Th–Pb age determination of kimberlitic perovskite using the large double-focusing Cameca IMS 1280. Linear relationships are found between ln(206Pb?+/U+) and ln(UO2+/U+), and between ln(208Pb?+/Th+) and ln(ThO+/Th+), based on which the inter-element fractionation in unknown samples during SIMS analyses can be precisely calibrated against a perovskite standard. The well-characterized Ice River perovskite is chosen as the U–Pb and Th–Pb age standard in this study. The 204Pb-correction method was used to estimate the fraction of common Pb, which is consistent with the results obtained using the 207Pb-based correction method for the dated perovskites of Phanerozoic age.A Tazheran perovskite with unusually high U but rather low Th yielded a Concordia U–Pb age of 462.8 ± 2.5 Ma and a Th–Pb age of 462 ± 4 Ma. Two perovskite samples from the Iron Mountain kimberlite have identical Concordia U–Pb ages of 410.8 ± 3.4 Ma and 411.0 ± 2.6 Ma, which are consistent within errors with their corresponding Th–Pb ages of 409.2 ± 7.2 Ma and 412.3 ± 3.3 Ma, respectively. Two perovskite samples from the Wesselton Mine of South Africa yielded indistinguishable 206Pb/238U ages of 91.5 ± 2.2 Ma and 90.3 ± 2.9 Ma, and Th–Pb ages of 90.5 ± 0.8 Ma and 88.4 ± 1.6 Ma, respectively. Accuracy and precision of 1–2% (95% confidence level) for these measurements have been demonstrated by the consistency of their U–Pb and Th–Pb ages with the recommended U–Pb ages of previous works. 相似文献
7.
Xian-Hua Li Weng-Guo Long Qiu-Li Li Yu Liu Yong-Fei Zheng Yue-Heng Yang Kevin R. Chamberlain De-Fang Wan Cun-Hua Guo Xuan-Ce Wang Hua Tao 《Geostandards and Geoanalytical Research》2010,34(2):117-134
We introduce a potential new working reference material – natural zircon megacrysts from an Early Pliocene alkaline basalt (from Penglai, northern Hainan Island, southern China) – for the microbeam determination of O and Hf isotopes, and U–Pb age dating. The Penglai zircon megacrysts were found to be fairly homogeneous in Hf and O isotopes based on large numbers of measurements by LA-multiple collector (MC)-ICP-MS and SIMS, respectively. Precise determinations of O isotopes by isotope ratio mass spectrometry (IRMS) and Hf isotopes by solution MC-ICP-MS were in good agreement with the statistical mean of microbeam measurements. The mean δ18O value of 5.31 ± 0.10‰ (2s) by IRMS and the mean 176Hf/177Hf value of 0.282906 ± 0.0000010 (2s) by solution MC-ICP-MS are the best reference values for the Penglai zircons. SIMS and isotope dilution-TIMS measurements yielded consistent 206Pb/238U ages within analytical uncertainties, and the preferred 206Pb/238U age was found to be 4.4 ± 0.1 Ma (95% confidence interval). The young age and variably high common Pb content make the Penglai zircons unsuitable as a primary U–Pb age reference material for calibration of unknown samples by microbeam analysis; however, they can be used as a secondary working reference material for quality control of U–Pb age determination for young (particularly < 10 Ma) zircon samples. 相似文献
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9.
It has been generally accepted that the South China Block was formed through amalgamation of the Yangtze and Cathaysia Blocks during the Proterozoic Sibaoan orogenesis, but the timing and kinematics of the Sibao orogeny are still not well constrained. We report here SHRIMP U–Pb zircon geochronological and geochemical data for the Taohong and Xiqiu tonalite–granodiorite stocks from northeastern Zhejiang, southeastern margin of the Yangtze Block. Our data demonstrate that these rocks, dated at 913 ± 15 Ma and 905 ± 14 Ma, are typical amphibole-rich calc-alkaline granitoids formed in an active continental margin. Combined with previously reported isotopic dates for the 1.0 Ga ophiolites and 0.97 Ga adakitic rocks from northeastern Jiangxi, the timing of the Sibao orogenesis is thus believed to be between 1.0 and 0.9 Ga in its eastern segment. It is noted that the Sibao orogeny in South China is in general contemporaneous with some other early Neoproterozoic (1.0–0.9 Ga) orogenic belts such as the Eastern Ghats Belt of India and the Rayner Province in East Antarctica, indicating that the assembly of Rodinia was not finally completed until 0.9 Ga. 相似文献
10.
Ling Xiao-Xiao Huyskens Magdalena H. Li Qiu-Li Yin Qin-Zhu Werner Ronald Liu Yu Tang Guo-Qiang Yang Ya-Nan Li Xian-Hua 《Mineralogy and Petrology》2017,111(2):163-172
Mineralogy and Petrology - Well-characterized matrix-matched natural mineral references of known age are an important prerequisite for SIMS (secondary ion mass spectrometry) U–Th–Pb... 相似文献