西藏冈底斯带东段强母错噶石英二长岩锆石U-Pb年龄、地球化学特征及地质意义

对出露于西藏冈底斯弧背断隆带东段的强母错噶石英二长岩进行了锆石U-Pb年代学和全岩地球化学分析,并据此探讨了该岩体的形成演化过程与成岩时的大地构造背景。测试结果表明,强母错噶石英二长岩中的岩浆锆石U-Pb加权平均年龄为(50.84±0.71) Ma(MSWD=0.51)为始新世早期。石英二长岩ω(SiO_2)=64.34%～64.87%,ω(K_2O)=4.66%～4.76%,ω(Na_2O)=3.38%～3.42%,ω(CaO)=3.65%～3.72%,ω(Al_2O_3)=15.91%～16.08%,全碱含量(K_2O+Na_2O)为8.04%～8.15%,K_2O/Na_2O=1.38～1.41,属于准铝质(A/CNK=0.91～0.93)钾玄岩系列。强母错噶石英二长岩轻稀土元素(LREE)含量为(241.62～441.75)×10~(-6),重稀土元素(HREE)含量为(18.58～20.60)×10~(-6),(LREE/HREE=12.48～21.65),稀土元素配分模式为轻稀土元素强烈富集的右倾型,其(La/Yb)_N为15.38～33.79,具中等负Eu异常(δEu=0.60～0.67)。微量元素显示强母错噶石英二长岩相对富集大离子亲石元素,而Nb、Ta、Ti和P等高场强元素(HFSE)相对亏损,显示出火山弧环境背景下中等分异程度的I型花岗岩特征。强母错噶石英二长岩的形成可能与冈底斯带始新世早期强烈的岩浆作用和新特提斯洋板片断离引发的地壳增厚密切相关,大洋板片断离从而引起软流圈物质上涌,导致下地壳部分熔融并与上涌地幔混合形成壳幔混合岩浆。     

苏鲁造山带岩浆岩的锆石U Pb定年及构造意义

锆石U-Pb定年和地球化学分析结果显示,苏鲁造山带南缘连云港锦屏山片麻状花岗岩形成于(806.0±14.0)Ma,海州群云台组变质火山岩形成于(800.8±7.8)Ma,张八岭隆起的张八岭群西冷组变质火山岩形成于(751.6±7.1)Ma和(767.0±15.0)Ma.这些岩浆岩总体上具有高钾钙碱性系列、右倾型REE(Rare Earth Elements)模式、Nb、Ta、Sr、P和Ti强烈亏损、中等负铕异常、重稀土弱到中等亏损、低Sr、高Yb等特点,与浙闽型岩浆岩反映的区域伸展环境和下地壳部分熔融是一致的.这次构造岩浆活动820～740Ma,是晋宁期主碰撞造山后Rodinia超大陆裂解和岩石圈减薄演化的记录.     

江南隆起（九岭）多阶段构造演化的花岗岩记录

以江南隆起九岭花岗岩体为研究对象,应用激光剥蚀等离子体质谱(LA-ICP-MS)锆石U-Pb定年技术,得到该花岗岩侵入年龄为853～811Ma.自晋宁期以来,九岭地区依次经历了加里东、印支及燕山等多阶段构造演化.通过花岗岩地球化学及构造图解分析,可知江南隆起九岭多阶段构造演化环境各不相同.晋宁期(929-810 Ma)花岗岩体落入岛弧与碰撞的过渡环境;而加里东期(439-411 Ma)花岗岩体具板内汇聚环境特点;燕山期(158-118 Ma)花岗岩形成于同碰撞兼火山弧构造环境.     

In situ U-Pb dating of titanite by LA-ICPMS

Titanite is an ideal mineral for U-Pb isotopic dating because of its relatively high U,Th and Pb contents.Here,we developed a technique for U-Pb dating of titanite using the 193 nm ArF laser-ablation system and Agilent 7500a Q-ICP-MS.Standards of titanite (BLR-1 and OLT-1) and zircon (91500 and GJ-1) were dated using single spot and line raster scan analytical methods.To check the matrix effect,titanite (BLR-1) and zircon (91500) standards were analyzed as the external standards.The weighted mean 206 Pb/238 U ages of OLT-1 titanite are 1015±5 Ma (2,n=24) and 1017±6 Ma (2,n=24) by single spot and line raster scan analyses,respectively,using BLR-1 titanite as the external standard.These ages are consistent with its reference age of about 1014 Ma.However,using 91500 zircon as the external standard,the weighted mean 206 Pb/238 U ages are 917±4 Ma (2,n=24) and 927±5 Ma (2,n=24) for BLR-1 titanite,and 891±4 Ma (2,n=24) and 901±5 Ma (2,n=24) for OLT-1 titanite by single spot and line raster scan analyses,respectively.It is evident that these ages are ～12% younger than their reference values.Our results reveal that significant matrix effect does exist between different kinds of minerals during LA-ICPMS U-Pb age determination,whereas it is insignificant between same minerals.Therefore,same mineral must be used as the external standard for fractionation corrections during in situ LA-ICPMS U-Pb age analysis.In addition,we determined U-Pb ages for titanites from the Early Cretaceous Fangshan pluton,which indicates a rapid cooling history of this pluton.     

铀系法年代学研究进展及在高原盐湖中的应用

 高原盐湖在形成的各个阶段,都详尽记录和保存着其咸化阶段的环境变化信息,是研究极端干旱气候的重要载体。年代学是盐湖古气候研究最重要的一项内容,也是后续研究工作的基础。目前除了最常用的¹⁴C定年、光释光（OSL）定年、电子磁悬共振（ESR）和古地磁定年等方法外,铀系法定年在盐湖沉积的年代学研究中也得到了广泛的应用。随着技术发展,铀系测年技术方法经历了α谱法、热电离质谱法（TIMS）再到多接受器电感耦合等离子体质谱技术（MC-ICP-MS）的不同发展阶段。而这些技术方法在不同时期和阶段对第四纪及高原盐湖的定年研究做出了一定的贡献。盐湖沉积中的碳酸盐黏土、石盐和石膏等盐类矿物都可以作为铀系定年的研究材料。随着质谱技术的发展,盐类矿物的微区定年也逐渐成为可能。同时,盐湖沉积中盐类矿物的铀系定年研究仍然有限,未来多开展这些方面的研究将对铀系测年技术在盐湖沉积中的应用产生积极作用。     

石英前剂量110℃热释光效应的研究

研究了不同前剂量照射对石英粉末１１０ ℃峰的热释光（ＴＬ）响应的影响,结果表明,石英１１０ ℃热释光效应正比于照射的前剂量,并且在前剂量范围（０．１３５～１ ．３５０ Ｇｙ）内,石英热释光灵敏度基本呈线性分布态势．     

马坝人地点南支洞铀系定年初步结果

报道马坝人地点南支洞次生碳酸盐岩和骨化石样的铀系年代. 根据表层钙板 2 个样品 3 次测试的平均结果,其下含化石堆积应早于 237 ka. 出自第二层堆积的骨化石样分析结果显著小于上覆表层钙板,可引为骨化石铀系年代结果可信度欠佳的例证. 基于洞穴地点骨化石样铀系年代总体偏低的认识,并基于南支洞与出土马坝人化石裂隙堆积层位相当的假设,我们认为可暂以南支洞表层钙板年代 (237 ka),代表马坝人化石的最小年代. 南支洞尚存较多的含化石堆积,多学科综合研究或可为马坝人的年代位置提供进一步的证据.     

基于年代数据的青藏高原东北部全新世风沙活动研究

本文对青藏高原东北部全新世风成沉积剖面的年代数据应用概率密度方法结合年代数据分布情况重建了该区全新世风沙活动历史.结果表明:青藏高原东北部早全新世风沙活动强烈,但也存在不同尺度的空间差异,表现在共和盆地、柴达木盆地及青海湖盆地风成砂都广泛发育,但青海湖盆地同期还有古土壤发育,冬给措纳湖流域在这一时期也有少量的风成砂层出现;中全新世古土壤广泛发育,风沙活动较弱,整个东北部具有较好的一致性;晚全新世以来,柴达木盆地和冬给措纳湖流域风成砂发育较好,而共和盆地古土壤广泛发育,同时青海湖盆地风成砂和古土壤均有出现,说明风沙活动强度的区域差异较大,这可能是由于局部地区受到了人为活动强烈干扰的影响.风沙活动强度与区域有效湿度密切相关,区域有效湿度较高时,风沙活动较弱;反之,风沙活动较强.另外,大面积湖泊的存在使得青海湖盆地和冬给措纳湖流域全新世风沙活动的特点与柴达木盆地和共和盆地不尽相同,湖泊水位与湖泊增湿降温效应的相互关系以及物源供给特点可能是造成这一现象的原因.年代数据的概率密度方法相对于频率统计直方图具有一定的优势,充分利用了单个年代数据符合正态分布的特点,能够反映年代数据的范围和精度.     

Rapid genome evolution in Pms 1 region of rice revealed by comparative sequence analysis

Pms1, a locus for photoperiod sensitive genic male sterility in rice, was identified and mapped to chromosome 7 in previous studies. Here we report an effort to identify the candidate genes for Pms1 by comparative sequencing of BAC clones from two cultivars Minghui 63 and Nongken 58, the parents for the initial mapping population. Annotation and comparison of the sequences of the two clones resulted in a total of five potential candidates which should be functionally tested. We also conducted com-parative analysis of sequences of these two cultivars with two other cultivars, Nipponbare and 93-11, for which sequence data were available in public databases. The analysis revealed large differences in sequence composition among the four genotypes in the Pms1 region primarily due to retroelement activity leading to rapid recent growth and divergence of the genomes. High levels of polymorphism in the forms of indels and SNPs were found both in intra- and inter-subspecific comparisons. Dating analysis using LTRs of the retroelements in this region showed that the substitution rate of LTRs was much higher than reported in the literature. The results provided strong evidence for rapid genomic evolution of this region as a consequence of natural and artificial selection.