激光质谱测定南极乔治王岛北海岸A635玄武岩微区^40Ar—^39Ar的等…

采用连续激光直接对岩石光片样品微区熔样，以高灵敏度、高精确度的质谱计测试，对南极乔治王岛玄武岩样品进行＾４０Ａｒ－＾３９－Ａｒ汪守年，取得了成功。样品置反应堆中心Ｅ－５孔道，以１．８×１０＾１８ｎ／ｃｍ＾２的快中子总通量照射，时间为５０ｈ，放射性冷却后进行测定。     

泥炭黄腐植酸产率的测定方法探讨

将实测的泥炭黄腐植酸平均含碳比用于容量法直接测定泥炭黄腐植酸产率的计算中，所得结果与间接差减法相比较无系统左偏差，避免了间接法繁琐手续，且与泥炭腐植酸总量测定连续进行，提高工效。对于平衡产率为１６．３３％的试样，用本法多次测定的相对标准偏差为２．５％。     

石笋高精度高分辨率年代学和古气候研究

古气候变化突变事件的发现和对未来环境变化的预测，提出了取得高分辨率古环境记录的要求。本文介绍了中国洞穴石笋年代学和古气候最新研究的进展以及目前我们用MAT－262质谱仪对洞穴石笋的TIMS铀系定年法对贵州荔波董歌洞、龙泉洞、衙门洞、贵州都匀七星洞洞穴次生碳酸盐石笋进行年代学研究的一些成果。     

不平衡铀系定年的新技术突破——高精度、高灵敏度238U-234U-230Th同位素质谱测定和应用

80年代中期发展起来的高精度、高灵敏度不平衡铀系热电离质谱定年新技术是同位素定年技术的一次革命性突破，并已在古气候、古环境、古海洋、考古学以及近代火山—岩浆作用研究中取得了一系列重要成果，本文介绍了这方面的研究进展。这一新技术已引起越来越广泛的重视，显示出巨大的应用前景。尽快开展不平衡铀系热电离质谱定年技术的应用，对提高我国的高分辩率第四纪年代学分析技术和应用研究水平有重要意义。     

Geochemical characteristics and spectrometric prospecting in the muscovite-bearing pegmatites and granites,southeastern Aswan,Egypt

Rare metal mineralization of Sn, Nb-Ta and W is encountered in the Gebel Dihmit area （GDA）, southeastern Aswan, Egypt. The mineralization is related to muscovite granites and their pegmatite derivatives. The pegmatites are divided into three types according to their main mineral assemblages： K-feldspar-muscovite-tourmaline, K-feldspar-albite-muscovite and albite-K-feldspar-lepidolite veins. Petrogenetic studies indicate that Sn and Nb-Ta mineralization extends from the late-magmatic stage to the pegmatite and hydrothermal stages of the （GDA） suite. The albite-K-feldspar-lepidolite granite is composed dominantly of albite, lepidolote, and quartz, with topaz, K-feldspar and amblygonite. The accessory minerals are zircon, monazite, pollucite, columbite-tantalite, microlite and Ta-rich cassiterite. Phenocrysts of quartz, topaz and K-feldspar contain abundant inclusions of albite laths and occasional lepidolite crystals along growth zones （snowball texture）, indicating simultaneous crystallization from a subsolvus, residual magma. The origin of the pegmatites is attributed to extreme differentiation by fractional crystallization of a granitic magma. The economic potential for rare metals was evaluated in the geochemical discrimination diagrams. Accordingly, some of the pegmatites are not only highly differentiated in terms of alkalis, but also the promising targets for small-scale Ta and, to a less extent, Sn. The pegmatites also provide the first example of Fe-Mn and Nb-Ta fractionation in successive generations of granites to cassiterite-bearing pegmatites, which perfectly ex- hibit similar fractionation trends established for primary columbite-tantalite in the corresponding categories of pegmatites. Uranium and Th of magmatic origin are indicated by the presence of thorite and allanite, whereas evidence of hydrothermal mineralization is the alteration of rock- foring minerals such as feldspar and the formation of secondary minerals such as uranophane..     

地壳的变迁

地球从形成、演化发展46亿年来．留下了一部内容丰富的大自然的巨大史册，这就是各时代的地层：地质年代的划分是研究地球演化、了解各处地层所经历的时间和变化的前提：1881年，国际地质学会正式通过了至今通用的地层划分表，以后又不断进行修订、完善，形成了一张系统完整的地质年代表。