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71.
Chronological Study on Metallization of Endogenetic Metallic Deposits——An Example From Xihuashan Tungsten Deposit, South China 总被引:1,自引:0,他引:1
《科学通报(英文版)》1993,38(11):931-931
72.
《科学通报(英文版)》1996,41(13):1107-1107
73.
The ages of U-Pb and Sm-Nd for eclogite from the western segment of Altyn Tagh tectonic belt 总被引:10,自引:0,他引:10
The eclogites of Altyn Tagh tectonic belt occur as lens within gneisses characterized by amphibolite-facies mineral parageneses.
The well-preserved eclogite is selected for Sm-Nd and U-Pb isotopic dating. The Sm-Nd isotopic data yield a whole rock-garnet-omphacite
isochron of (500 ± 10) Ma. The U-Pb isotopic measurements of zircons show that the four grain populations are nearly concordant
and well plotted on concordia curves, giving a weighted mean age (503.9 ± 5.3) Ma. Two kinds of methods obtain a similar age
which reveals the peak metamorphic age of eclogites, and reflect the existence of orogenic root related to Caledonian subduction
and continent-continent collision. 相似文献
74.
Sm-Nd age dating of high-pressure granulites and amphibolite from Sanggan area, North China craton 总被引:4,自引:0,他引:4
The high pressure (HP) metamorphic age has been dated to HP rocks from the Sanggan area, North China craton. We have got garnet+whole rock isochron ages of (1 842±38) Ma for HP granulite, and (1 856 ± 26) Ma for HP amphibolite. The Sm-Nd whole rock isochron of HP granulites give out an age of (1 870±150) Ma with Nd depleted mantle model age of (2 402—2 482) Ma. Considering the Nd isotope homogenization during the peak metamorphism of the HP granulite, Sm-Nd closure temperature and the retention of Nd isotopic memory in garnets partially broken down during decompression, all these isochron ages are thought to be HP metamorphic age. Furthermore, we proposed that the HP metamorphism took place at the end of Paleoproterozoic during the large-scale collision and assembly of the North China craton. 相似文献
75.
76.
A group of Rb-Sr ages, i.e. plagioclase-whole rock (WR) isochron age of (205 ± 7) Ma, hornblende-WR isochron age of (164 ± 10) Ma and biotite-WR isochron age of (123.4 ± 1.2) Ma, for one pyroxenite sample from Renjiawan in North Dabie Terrane (NDT) are reported. According to the closure temperature of 600℃ for plageoclase and 300℃ for biotite, the Renjiawan pyroxenite should intrude into the NDT before 205 Ma, and the younger Rb-Sr ages may reflect the cooling history of the intrusion or reset by the very strong Cretaceous thermal event in NDT. 相似文献
77.
利用小波技术以沈阳昭陵古油松为样本建立的古油松年轮宽度年表与太阳黑于活动为研究对象,分析了沈阳的古油松生长与太阳活动的关系。油松在5~8年、10-12年和20-30年周期段对太阳活动表现出积极的响应,呈现5.8、11.5和27.2年的强周期震荡,响应信号在太阳活动的主周期11.1年左右表现最强。太阳黑子活动对油松年轮宽度年表总的影响是负效应,是多种抑、促效应的复合。 相似文献
78.
79.
汪前进 《广西民族大学学报》2006,12(2):13-27
从文献的角度按时间序列尽量弄清黄河及其支流究竞在何时、何地出现河清,持续多久、发生的范围及其程度,以及朝野做出的反映与采取的行动. 相似文献
80.
Newly discovered Palaeolithic artefacts from loess deposits and their ages in Lantian,central China 总被引:1,自引:0,他引:1
Shejiang Wang Huayu Lu Hongyan Zhang Xuefeng Sun Shuangwen Yi Yingyong Chen Gaike Zhang Luda Xing Weigang Sun 《科学通报(英文版)》2014,59(7):651-661
Eight new Palaeolithic open-air sites were identified and 770 stone artefacts were collected from 2009 to 2011 in the Lantian area of the Bahe River valley, central China. Because the famous Homo erectus fossils were unearthed at the Gongwangling and Chenjiawo localities, and more than 30 Palaeolithic open-air sites were investigated in the 1960s in this region, the catchment of Bahe River is regarded as one of the most important hominin sites from the late early Pleistocene to the middle Pleistocene. These eight newly discovered open-air sites are located at the second(n = 6), third(n = 1) or higher terraces(n = 1) of the Bahe River. The Diaozhai section on the second terrace was sampled in detail. Two samples were collected for optically stimulated luminescence dating(OSL). The OSL results suggest that a buried lithic artefact layer at the Diaozhai site spans approximately 70–30 ka. The lithic assemblage analysis suggests that the stone artefacts were made of local pebbles/cobbles such as greywacke, quartz, sandstone and igneous rocks. The main percussion techniques that were used were direct hard hammer percussion and bi-polar techniques. The lithic artefacts comprise hammer stones, cores, flakes, retouched tools and flaking debris. Acheulian-type large cutting tools(LCTs) such as hand-axes, picks and cleavers were indentified in the Lantian region as well. This is the first time Acheulian-type LCTs from the late Pleistocene have been identified in this region. This study distinguishes age gaps between Western world and East Asian Acheulian-type tools. 相似文献