现代沉积的²¹⁰Pb计年   总被引：74，自引：10，他引：74       下载免费PDF全文

万国江 《第四纪研究》1997,17(3):230-239

²¹⁰Pb具有百年时间尺度沉积计年的重要价值。²¹⁰Pb_ex计年假设：沉积物是封闭系统；进入水体的²¹⁰Pb能有效地转移到沉积物中并不发生沉积后迁移；非过剩²¹⁰Pb与其母体²²⁶Ra保持平衡。²¹⁰Pb_ex计年可用稳定输入通量-稳定沉积物堆积速率模式、常量初始浓度模式或恒定补给速率模式。沉积物柱芯必须保持原态并以0．5～1cm间隔分截；用相应层节²²⁶Ra校正。沉积物表层混合作用及²²²Rn的丢失可能导致顶部²¹⁰Pb_ex异常。季节性缺氧湖泊沉积物顶部可能存在²¹⁰Pb及²¹⁰Po的再迁移。²¹⁰Pb与¹³⁷Cs两种计年方法原理上具有根本差别。²¹⁰Pb，¹³⁷Cs与沉积纹理方法对比是准确计年的重要保证。  相似文献   

扬子地块西缘灯影组层控铅锌矿床成因的地球化学论证   总被引：5，自引：0，他引：5  

邵世才  李朝阳 《矿物岩石地球化学通报》1997,(1)

扬子地块西缘灯影组层控铅锌矿床成因的地球化学论证邵世才（有色总公司北京矿产地质研究所，北京１０００１２）李朝阳（中国科学院地球化学研究所，贵阳５５０００２）关键词层控铅锌矿床地球化学矿床成因扬子地块西缘１矿床地质特征扬子地块西缘灯影组铅锌矿床呈南北向...  相似文献   

滇黔桂微细浸染型金矿铅同位素组成及应用   总被引：6，自引：1，他引：6  

刘显凡  刘家军  朱赖民  卢秋霞 《矿物岩石地球化学通报》1997,(3)

滇黔桂微细浸染型金矿铅同位素组成及应用＊刘显凡刘家军朱赖民（中国科学院地球化学研究所，贵阳５５０００２）卢秋霞（成都理工学院，成都６１００５９）关键词微细浸染型金矿铅同位素组成矿质来源上地幔分异混染滇黔桂１矿床地质背景研究区位于扬子地台西南缘与华南加...  相似文献   

祁连山西段及酒西盆地区第四纪构造运动的阶段划分   总被引：25，自引：6，他引：25  

陈杰  卢演俦  丁国瑜 《第四纪研究》1996,16(3):263-271

通过沉积地层、地貌、构造形变等的综合研究，对祁连山西段及酒西盆地区第四纪构造运动的期次和阶段进行了划分。上新世晚期以来，这一地区至少经历过６次显著的构造变动或构造事件，其中以玉门、酒泉和白杨河运动最为强烈。针对上述构造事件进行了古地磁、孢粉、红外释光和热释光等方法的综合研究和年龄测定，论述了各阶段构造运动的方式、性质和其它有关特征。  相似文献   

九甸峡工程区断层测年结果研究与讨论   总被引：2，自引：0，他引：2  

储同庆  张韵 《工程地质学报》1996,4(4):61-68

断层的年代测定是研究断层活动性的重要内容之一。然而, 一个工程同一条断层会出现不同的测年结果, 从而引起争议和难予决断。近年来我们通过几个大型工程区域稳定性研究, 对此获得了一些认识。本文以洮河九甸峡地区几条主干断层为研究对象, 采用同位素年龄测定与野外地质调查和显微构造分析相结合的方法, 对断层测年问题作一分析和讨论, 也许对岩土工程断层活动性研究有一定参考价值。  相似文献   

大别山超高压石榴多硅白云母片岩中钻石U－Pb年龄   总被引：2，自引：0，他引：2  

刘晓春  李惠民  左义成 《矿物岩石地球化学通报》1996,(1)

大别山超高压石榴多硅白云母片岩中钻石Ｕ－Ｐｂ年龄刘晓春（中国地质科学院地质力学研究所，北京１０００８１）李惠民，左义成（地质矿产部天津地质矿产研究所，天津３００１７０）关键词石榴多硅白云母片岩，Ｕ－Ｐｈ年龄，早元古代表壳岩，印支期超高压变质，大别山高...  相似文献   

Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate?     

A. Bollhöfer  A. Eisenhauer  N. Frank  D. Pech  A. Mangini 《International Journal of Earth Sciences》1996,85(3):577-585

Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution²³⁰Th_excess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got values of 0.06–0.59 ppb (²³⁰Th), 0.43–1.40 ppm (²³²Th), 0.09–0.49 ppb (²³⁴U) and 1.66–8.24 ppm (²³⁸U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the²³⁰Th_excess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant²³⁰Th_excess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios.  相似文献   

U—Series Dating of Fossil Bones：Results from Chinese Sites and Discussions on Its Reliability     

沈冠军 《中国地球化学学报》1996,15(4):303-313

Calculations,according to some open-system models,point out that while a statistically significant discrepancy between the results of two U-series methods,^230Th/^234U and ^227Th/^220Th(or ^231Pa/^235U),attests a relatively recent and important uranium migration,concordant dates cannot guarantee closes-system behavior of sample.The results of 20 fossil bones from 10 Chinese sites,19 of which are determined by two U-series methods,are given,Judging from independent age controls,8 out of the 11 concordant age sets are unacceptable,The results in this paper suggest that uranium may cycle into or out of fossil bones,such geochemical events may take place at any time and no known preserving condition may securely protect them from being affected.So for the sitew we have studied,the U-series dating of fossil bones is of limited reliability.  相似文献   

桂东北铅锌矿床生物成因的初步研究     

梁书艺 《矿物岩石》1997,17(1):90-95

作者在桂东北发现由生物－热卤水作用形成的新类型铅锌矿床，本文提供了生物成因的硫、碳同位素证据并着重讨论矿床的生物成因。矿床产于寒武－奥陶系与下泥盆统间不整合面之下的构造角砾破碎带，有机碳含量高的地段对矿化有利。生物组构和生物踪迹在金属硫化物和蚀变岩中普遍可见  相似文献   

南极乔治王岛中——新生代岩浆岩Sr—Nd—Pb同位素组成及源区特征   总被引：7，自引：1，他引：7  

邢光福  陶奎元 《岩石学报》1997,13(4):473-487

对乔治王岛１１个火山岩和２个侵入岩样品做了Ｓｒ－Ｎｄ－Ｐｂ同位素分析，其中（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７０３２６～０．７０３９２，εＮｄ＝３．０２～６．７２，２０６Ｐｂ／２０４Ｐｂ＝１７．７７６～１８．５１５，２０７Ｐｂ／２０４Ｐｂ＝１５．．５０６～１５．５７１，２０８Ｐｂ／２０４Ｐｂ＝３７．８６８～３８．３０８。根据以上同位素组成及其相互关系并结合岩石学和微量元素特征及火山岩中熔融包裹体成分，得出以下结论：（１）研究的乔治王岛岩浆岩起源于亏损地幔（ＤＭＭ）和地幔流体交代成因的富集地幔ＥＭＩ混合形成的源区；（２）该源区具有广义Ｄｕｐａｌ异常，它正是由于ＥＭＩ组份加入即通过流体交代作用而产生的；（３）流体主要是俯冲深海沉积物脱碳酸盐作用而释放出的富ＣＯ２流体。  相似文献