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51.
本文以连山关花岗岩体为例,指出该区古老花岗岩体2种锆石可以作出3组U-Pb一致线交点年龄,分析了这3组年龄间的相互关系及其所代表的意义,并提出一种可能求出岩体上限年龄的方法。 相似文献
52.
Considerable attention has been paid in recent years to the study of geothermal history by using spontaneous fission tracks of 238U recorded in minerals.Apatite and zircon were used for fission track study in this paper because apatitie has been widely used as a natural geothermometer(Wang Shicheng et al., 1994) to reveal the thermal evolution of sedimentary rocks based on its low annealing temperature of fission tracks and zircon is characterized by a closing temperature above 700℃,The samples were collected from ferruginous,siliceous slate wall rock at the upper levels of the orebody and Nb-REE-Fe ores from deep tunnels.The age and thermal evolution of the orebody were discussed in terms of fission track characters and their length variations observed in the coexisting apatite and zircon in the same specimen. 相似文献
53.
Presented in this paper are the newly obtained grain zircon U-Pb ages of volcanic rocks of the Lueliang Goup and associated Kuanping granitic migmatitic gneiss in Shanxi Province.The zircon U-Pb ages of bimodal volcanic rocks(basalt and rhyolite)of the Upper Lueliang Group indicate that the rocks erupted at about 2100 Ma.So the Lueliang Group was formed during the Early Proterozoic.In the area studied the second-stage metamorphism experienced by the Lueliang Group is the dominant one which took place at about 1806 Ma.i.e.,during the late Early Proterozoic. 相似文献
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55.
Mineralization Ages of the Jiapigou Gold Deposits,Jilin 总被引:1,自引:0,他引:1
Li Junjian Shen Baofeng Mao Debao Li Shuangbao Zhou Huifang Cheng Yuming Tianjin Institute of Geology Mineral Resources Chinese Academy of Geological Sciences Tianjin Nonferrous Metal Geological Exploration Bureau Changchun Jilin 《《地质学报》英文版》1997,71(2):180-188
The Jiapigou gold deposits are typical vein type deposits associated withArchaean greenstone belts in China. According to the crosscutting relationships between dykesand auriferous veins, single hydrothermal zircon U-Pb dating and quartz K-Ar,~(40)Ar-~(39)Ar andRb-Sr datings, the main mineralization stage of the Jiapigou deposit has been determined to be2469-2475 Ma, while mineralization superimposition on the gold deposit occurred in1800-2000 Ma and 130-272 Ma. They form a mineralization framework of one oldermetallogenic epoch (Late Archaean-Early Proterozoic) and one younger metallogenic epoch(Mesozoic) of gold deposits in Archaean greenstone belts in China. 相似文献
56.
北秦岭德河黑云二长花岗片麻岩体的成岩时代--TIMS和SHRIMP锆石U-Pb同位素年代学 总被引:17,自引:6,他引:17
德河黑云母二长花岗片麻岩体侵位于秦岭造山带北秦岭前寒武纪变质岩系内,遭受了强烈的变形作用改造,具有典型S型花岗岩的矿物组成特征。TIMS和SHRIMP法锆石U-Pb同位素年龄测定结果分别为(964.4±5.2)Ma和(943±18)Ma,两者在误差范围内是一致的。鉴于SHRIMP法锆石微区测年具有更好的代表性,建议以(943±18)Ma代表德河黑云母二长花岗片麻岩的侵位时代。 相似文献
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蕲春花岗质杂岩体包括斑状二长花岗岩和花岗岩两部分,它们之间在化学性质上存在着很大的差异,前者表现为高Al 2O3(15.73%)、相对高CaO(2.46%)、Na2O含量明显高于K2O(Na2O/K2O=1.27),尤以强烈亏损重稀土元素和极强的轻、重稀土元素分馏程度[(La/Yb)N=46.8]为特征而类似于太古宙高Al2O3的TTG岩石.而后者则以较低的Al2O3含量(14.05%)、贫CaO(0.82%)、K2O含量明显高于Na2O(Na2O/K2O=0.81)为特征,轻、重稀土元素的分馏程度[(La/Yb)N=10.89]也较片麻状二长花岗岩中弱得多.两类岩石中锆石的U-PbSHRIMP年龄分别为824.6±17.6 Ma和784±20 Ma,该时代与大别山造山带内花岗片麻岩的原岩形成年龄类似.大别山造山带内弱变质-未变质晋宁期花岗岩的出现表明扬子板块印支期向北俯冲时,该花岗质杂岩处于俯冲板片的后缘,可代表造山带内扬子基底的原地露头.而岩体周围的高压变质杂岩应是折返上来的无根构造岩片,大别山造山带内高压超高压变质杂岩的出露不是整体性抬升剥蚀的结果. 相似文献
59.
江西大吉山五里亭花岗岩一直被认为是与大吉山钨矿有关的早阶段花岗岩体 ,时代为燕山早期。但实际上大吉山地区各阶段花岗岩体之间的时空关系并不清楚 ,前人的某些年龄数据也存在相互矛盾之处。本文利用单颗粒锆石 U - Pb化学法 ,对五里亭花岗岩进行了年代学研究 ,获得 2 38.4± 1Ma的岩体侵位年龄 ,这个年龄属印支期。本文还结合某些岩石学、地球化学特征研究及与相邻岩体的对比 ,认为五里亭花岗岩确应归属于印支期 ,因此 ,五里亭岩体与大吉山钨矿没有成因上的直接联系。五里亭花岗岩侵位年龄的厘定和该地区更多印支期花岗岩的不断发现 ,表明印支运动在华南的影响超出了人们以往的认识。在此基础上 ,本文还对华南印支运动和印支期花岗岩的问题进行了简单的讨论 相似文献
60.
The Sanchazi mafic-ultramafic complex in Mianlue tectonic zone, South Qinling can be subdivided into two blocks, i.e. Sanchazi paleo-magmatic arc and Zhuangkegou paleo-oceanic crust fragment (ophiolite). The Sanchazi paleo-magmatic arc is mainly composed of andesite, basaltic and basalt-andesitic gabbro (or diorite), andesitic dyke, plagiogranite and minor ultramafic rocks, which have typical geochemical features of island arc volcanic rocks, such as high field strength element (e.g. Nb, Ti) depletions and lower Cr, Ni contents. The Light rare earth element (LREE) and K enrichments of these rocks and zircon xenocrystals of 900 Ma from plagiogranite suggest that this magmatic arc was developed on the South active continental margin of the South Qinling micro-continent. The U-Pb age of (300 ± 61)Ma for zircons from plagiogranite indicates that the Mianlue paleo-oceanic crust was probably subducted underneath the South Qinling micro-continent in Carboniferous. This is consistent with the formation time (309Ma) of the Huwan eclogite originating from oceanic subduction in Dabie Mountains, suggesting that the Mianlue paleo-ocean probably extended eastward to the Dabie Mountains in Carboniferous. The high-Mg adakitic rocks in Sanchazi paleo-magmatic arc suggest that the subducted oceanic crust was relatively young (<25Ma) and hot. 相似文献