Petrogenesis and significance of early Yanshanian syenite-granite complex in eastern Nanling Range   总被引：4，自引：2，他引：4  

CHEN Peirong  ZHOU Xinmin  ZHANG Wenlan  LI Huimin  FAN Chunfang  SUN Tao  CHEN Weifeng & ZHANG Min . State Key Laboratory of Mineral Deposits Research  Department of Earth Sciences  Nanjing University  Nanjing  China  . Tianjin Institute of Geology  Mineral Resources  China Geological Survey  Tianjin  China 《中国科学D辑(英文版)》2005,48(7)

According to the statistics for granitoid distribution map of 1/2000000 Nanling region[1], the granitoids in the Nanling region sum up an area of more than 170000 km2, occupying about one fifth of the entire Nanling region. Granitoid rocks in the Nanlingregion are mainly composed of monzogranites (occu- pying more than 84%), granodiorites (about 11%) and syenogranites (about 3%)[2]. There also exists a small amount of syenites (0.12%) with a sum area of about 94 km2[2]. However, nearly half …  相似文献   

哀牢山-金沙江碱性岩带南段云南金平八一村钾质碱性花岗岩锆石SHRIMP U-Pb年龄   总被引：7，自引：4，他引：7  

林清茶  夏斌  张玉泉  王彦斌 《地质通报》2005,24(5):420-423

云南省金平县八一村钾质碱性花岗岩中的锆石由岩浆锆石和岩浆复合型锆石(老核新壳锆石)组成，以后者居多。锆石定年结果表明，岩浆锆石和岩浆复合型锆石的新壳SHRIMP U-Pb年龄为37Ma，反映岩浆上侵定位时的结晶时间，相当于始新世晚期。锆石老核获得的最大年龄为510Ma和177Ma，相当于晚寒武世和中侏罗世，表明该岩体保存有寒武纪和侏罗纪地质事件信息，而42～48Ma年龄可能是混合年龄。最后对锆石的成因和花岗岩的成岩机制等进行了初步探讨。  相似文献   

新疆东天山秋格明塔什——黄山韧性剪切带^40Ar／^39Ar年代学研究   总被引：17，自引：1，他引：17       下载免费PDF全文

陈文孙枢  张彦肖文交  王义天王清利姜立丰  杨俊涛 《地质学报》2005,79(6):790-804

秋格明塔什—黄山巨型韧性剪切带产出在东天山北部,其活动时期的系统厘定对东天山大地构造演化极为关键,因而对揭示中亚造山带南部晚期的历史有着重要意义。系统的Ar-Ar同位素年代学研究表明,该剪切带的活动在时间上具有多期性:剪切带早期为挤压推覆剪切作用,发生于300Ma之后,至少延续到了283.7Ma,但在280.2Ma时已经终止;晚期为右行走滑剪切变形作用,主活动期的时代为262.9～242.8Ma,历时近20Ma。在右行走滑剪切变形阶段,秋格明塔什—黄山韧性剪切带出现差异抬升现象,导致剪切带不同区段糜棱岩的同位素年龄有较大差别:剪切带中—西段(康古尔地区)走滑剪切变形作用产生的糜棱岩的时代为262.9～256.1Ma,快速抬升发生在262.9～261.5Ma,冷却速率>100℃/Ma。剪切带东段(土屋—延东地区)走滑剪切变形作用产生的糜棱岩的时代为247.1～242.8Ma,快速抬升发生在247.1～246.9Ma期间,冷却速率>200℃/Ma。结合区域地质资料,笔者认为早期的挤压推覆剪切作用可能与东天山晚古生代板块俯冲—碰撞过程有关,而晚期的走滑剪切变形则可能反映了东天山北部地区碰撞后陆内变形特征。  相似文献   

北祁连山寒山金矿成矿时代讨论   总被引：6，自引：1，他引：6  

宋忠宝  任有祥  李智佩  杨建国  栗亚芝 《地质与勘探》2005,41(3):12-15

寒山大型金矿是近年来在北祁连山西段发现的与基性火山岩有关的构造蚀变岩型金矿.作者利用Rb-Sr同位素方法测得寒山金矿的成矿时代为339 Ma,属华力西期.指出寒山金矿的成矿时代应为(303～339)Ma,有多期热液叠加,多期成矿作用.因此,作者认为寒山金矿的热液很可能是青山斜长花岗岩(370±25Ma)、寒山辉长岩(347.1±6.4Ma)共同提供的.由于该区有较多的中酸性岩体存在,现成矿时代的确定对于该区在寻找华力西期-加里东晚期蚀变岩型金矿具有重要意义.  相似文献   

Cosmogenic nuclide chronology of pre-last glacial maximum moraines at Lago Buenos Aires, 46°S, Argentina     

Michael R. Kaplan  Daniel C. Douglass  Bradley S. Singer  Robert P. Ackert  Marc W. Caffee 《Quaternary Research》2005,63(3):636-315

At Lago Buenos Aires, Argentina, ¹⁰Be, ²⁶Al, and ⁴⁰Ar/³⁹Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000–16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/10³ yr, both yield a common estimate age of 150,000–140,000 yr for the two moraines. The erosion rate estimate derives from ¹⁰Be and ²⁶Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded ⁴⁰Ar/³⁹Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation.  相似文献   

Sedimentary-volcanic tufts formed during the early Middle Triassic volcanic event in Guizhou Province and their stratigraphic significance     

XIAO Jiafei 《中国地球化学学报》2005,24(4):338-344

The sedimentary-volcanic tuff （locally called ＂green-bean rock＂） formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements （ REE）, as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.  相似文献   

长江三角洲（江南）地区第四纪海侵层的划分及时代归属   总被引：1，自引：0，他引：1  

于振江郭盛乔  梁晓红张于平 王润华 《地层学杂志》2005,29(11):618-625

依据多年积累的钻孔剖面、微体生物化石、孢子花粉、古地磁和“C测年等资料综合分析研究，本区第四系有5个主要海侵层，从老到新为第V海侵层（宝山海侵）、第Ⅳ海侵层（嘉定海侵）、第Ⅲ海侵层（昆山海侵）和第Ⅱ海侵层（涌湖海侵）、第1海侵层（镇江海侵），其时代分别为早更新亚世中期（1．8-2．0Ma B．P．）、中更新亚世早期（0．78-0．45MaB．P．）、晚更新亚世早期（126～70Ka B．P．）、晚更新亚世晚期（40-20Ka B．P．）、全新世（始于10Ka B．P．）。  相似文献   

柴达木盆地北缘滩间山群新厘定   总被引：12，自引：0，他引：12  

李峰  吴志亮  李保珠  汪林峰 《西北地质》2006,39(3):83-90

滩间山群是柴达木盆地北缘早古生代重要的火山-沉积建造,总体为一套绿片岩相和强烈变形岩石。基于野外地质特征、古生物组合、同位素年龄、构造-热事件和火山-沉积演化等的综合分析,笔者认为滩间山群形成于早—晚奥陶世,同位素年龄在496~440Ma。重新厘定的滩间山群从老到新岩石地层单位有:早—中奥陶世火山-碎屑岩组;晚奥陶世沉积岩组;晚奥陶世熔岩-次火山岩组。原滩间山群c岩组(紫色砂砾岩组)变质微弱,仅达千枚岩相,与晚奥陶世熔岩-次火山岩组间呈角度不整合接触。其中的泥质岩Rb-Sr等时线年龄为313±1.0Ma(代表其千枚岩相的变质年龄),将其从滩间山群中剥离,归属早志留世。新的层序总体反映柴北缘早古生代经历了大陆裂谷开合的演化过程。  相似文献   

华北克拉通桑干地区高压麻粒岩的锆石SHRIMP U-Pb年龄及其地质含义   总被引：14，自引：0，他引：14  

张华锋  翟明国  彭澎 《地学前缘》2006,13(3):190-199

为了揭示华北克拉通桑干地区古元古代高压麻粒岩变质峰期时限,对选自该区的两个高压麻粒岩样品(DST02,XYS01)进行了锆石SHRIMP U-Pb测年。锆石样品的阴极发光图像显示为球形和无内部结构,Th/U比值变化为0.01~0.93。这些特征表明两样品的锆石应属于变质成因锆石。两样品的SHRIMP测年结果分别给出(1 792±12)Ma和(1 891±46)Ma。根据前人的年代学方面的研究成果,特别是未变质强过铝花岗岩中获得的1 900~1 850 Ma的锆石U-Pb年龄(郭敬辉等,2002)结果来看,本区高压麻粒岩峰期变质时代不会晚于此。因此本文获得的1 850~1 800 Ma的锆石SHRIMP U-Pb年龄应代表退变年龄。而(1 891±46)Ma的年龄限定了峰期高压变质年龄上限。  相似文献   

甘肃北山红尖兵山钨矿床的⁴⁰Ar-³⁹Ar同位素年代学研究   总被引：8，自引：2，他引：8  

江思宏  聂凤军 《矿床地质》2006,25(1):89-94

文章对红尖兵山钨矿云英岩中的白云母进行了40Ar-39Ar同位素年代学研究,获得的坪年龄为(216.6±1.6)Ma(2σ),等时线年龄为(215.2±2.8)Ma,MSWD=0.47,40Ar/36Ar初始比值为333±47。等时线年龄与坪年龄在误差范围内完全一致,可认为该结果近似代表了黑钨矿的形成时代,即红尖兵山的黑钨矿形成于印支期。  相似文献