14C dating of moss peat banks in Fildes Peninsula, Antarctica

Based on the radiocarbon data of the moss peat banks in Fildes Peninsula, Antarctica, it was calculated that the mean rates of peat accumulation in the upper layer and the lower layer are 0.195 and 0.069 4 mm · a^™1 respectively. Based on the radiocarbon date (3 265 ± 120 aBP) and the mean rate of peat accumulation in the lower peat layer, it was calculated that the age of the coast terrace on which the moss peat bank occurs is earlier than 4 300 aBP. During the past 4 300 years the coast terrace has risen about 18 m without apparently being destroyed, and the age of the glacier retreating process in this area is also earlier than 4 300 aBP.     

黔西南贞丰水银洞基性岩锆石U-Pb测年及金矿成矿

基性岩与金矿成矿关系密切。而针对滇黔桂地区卡林型金矿成矿年龄一直缺乏年代学证据。测得黔西南贞丰水银洞基性岩锆石U-Pb年龄为218±3.2 Ma,与前人对水银洞卡林型金矿年龄的测定一致,说明该区金矿化与基性岩岩浆活动密切相关。该年龄对应印支晚期,并在此基础上提出一种印支期成矿的动力学模型:古特提斯洋封闭导致印支板块与扬子板块碰撞,强大的区域构造事件为矿化提供了动力,形成了贞丰地区218±3.2 Ma的基性岩。另外该地区可能存在一些埋藏的印支期花岗岩侵入体,这些入侵的岩体可作为热源,驱动主要为大气降水成因的流体浸出成矿元素,形成了贞丰水银洞地区卡林型金矿床。     

大兴安岭柴河白音高老组流纹岩锆石U-Pb定年及成因探讨

为了研究大兴安岭中段柴河地区白音高老组流纹岩的形成时代和岩石成因,进行了锆石U-Pb同位素年龄测试和地球化学研究.LA-ICP-MS锆石U-Pb定年结果显示,白音高老组流纹岩形成于年龄为129~137 Ma的早白垩世.岩石地球化学研究表明,白音高老组流纹岩具有高硅富碱、贫钙镁的特征;稀土丰度总量m(∑REE)=121.35×10-6~194.92×10-6,轻重稀土分馏明显,m(La)/m(Yb)N=12.2~21.7,Eu负异常(δ_(Eu)=0.39~0.61),微量元素以富集Rb,Ba,Th,K,亏损Nb,Sr,P,Ti为特征;白音高老组流纹岩原始岩浆来源于上地壳岩石的部分熔融.     

Ages and tectonic significance of the collision-related granite porphyries in the Lhunzhub Basin, Tibet, China

The Paleocene collision-related granite porphyries are identified for the first time along the western margin of the Lhunzhub Basin, Tibet. SHRIMP U-Pb zircon analysis indicates that the granite porphyries were emplaced at 58.7±1.1 Ma (MSWD = 0.79) during the Indo-Asian continental collision. The granite porphyries are peraluminous and high in K, belonging to the calc-alkaline to high-K calc-alkaline series. They are relatively enriched in LILE, Th and LREE and depletion in Ba, Nb, P and Ti, characterized by LREE-enriched patterns with slightly to moderately negative Eu anomalies. These Paleocene granite porphyries are interpreted as the products generated by partial melting of the pre-existing arc crustal rocks caused by the increase of pressures and temperatures during the crustal shortening at the early stages of the Indo-Asian continental collision since 65 Ma. Despite inherited geochemical features and tectonic settings of the arc protoliths, they are significantly different from the volcanic rocks of the Dianzhong Formation within the Linzizong Group and the Miocene granite por- phyries in the Gangdise belt.     

第四纪早期丽蚌的电子自旋共振(ESR)年龄测定与泥河湾动物群的年代

对化石进行电子自旋共振(ESR)研究是近几年发展起来的一种新的测定年代技术.本文介绍了这种技术的基本原理和测定方法.应用ESR 方法对我国北方第四纪早期标准地层——泥河湾地层中部所产丽蚌化石进行了测定,并得到两个样品的年龄,分别为1.37±0.20和1.22±0.18百万年.初步确定,泥河湾地层中一个层段(第二层段)的形成年代应属早更新世晚期,而泥河湾动物群的年代应属早更新世中晚期.     

闽江河口第四纪地层划分和地质年代研究

本文系统地研究了闽江河口琅岐岛钻孔揭示的第四纪地层。根据孢粉、微古、硅藻和~(14)C测年等资料分析了沉积物形成时的气候波动、沉积相和沉积物年代,将闽江河口第四纪地层划分为上更新统上段(厚>15米)和全新统(厚49.80米)。全新统又可分为下全新统下段和上段、中全新统和上全新统。气候演化为:冷干→温暖略干→温暖湿润→炎热潮湿→温暖略干。沉积相演化为:冲积相、冲洪积相、湖沼相→冲积相、湖沼相→河口相、湖沼相→海湾相→河口相。     

青海沱沱河地区侵入岩体锆石U-Pb定年及其地质意义

青海沱沱河地区1∶5万(I45E009024、I45E010024、I46E009001、I46E010001)四幅区域地质调查发现,区内侵入岩发育差,岩性主要为花岗闪长斑岩,为该区域内首次发现的侵入岩体。通过对该花岗闪长斑岩进行LA-CIPMS锆石U-Pb同位素年龄测定,14个锆石测点中10个测点的测定值位于207Pb/235U-206Pb/238U一致线上,其206Pb/238U年龄在36~42 Ma之间,加权平均年龄为38.58±0.87 Ma,该年龄基本代表了花岗闪长斑岩的形成时间。从区域地质条件分析,将该岩体的形成时代确定为始新世。     

Re-Os dating of pyrite from Giant Bayan Obo REE-Nb-Fe deposit

The giant Bayan Obo REE-Nb-Fe deposit is locatedat the northern margin of the North China Block, i.e. atlatitude 41.7° north and longitude 110.0° east. The depositis very special in the world because it is the largest LREEdeposit and the second largest Nb deposit in the world,and also a large iron deposit. Geological features, mineralassemblage and geochronology of the deposit have beenreported[1—6]. However, various dating methods gave dif-ferent mineralization ages, and discrepancie…     

ISEA reversed event in the Cretaceous Normal Super-chron （CNS）： ^40Ar／^39Ar dating and paleomagnetic results

ThegeomagneticfieldwasfoundtobeofnormalpolarityforalongtimeduringtheCretaceousbyHelsleyandSteiner[1]andthiswaslaternamedasCretaceousNormalSuperchron(CNS)[2].TheCNSlastedalmost37Ma(120—83Ma).Severalabnormalgeologicalevents,suchasanoceanicanoxicevent,alargenumberofvol-canismandglobalclimaticwarmingduringtheCNShavebeenreported[3—11].Thishasledtomanyquestionsbeingraised.IsittruethattheEarthsmagneticfielddidnotreverseatallintheCNS?Ifitdidreverse,howmanytimesandwhendidthishappen?Istherea…