东秦岭陡岭群变质杂岩Sm-Nd、Rb-Sr、40Ar/39Ar、207Pb/206Pb年龄

本文用单颗粒锆石逐级蒸发２０７Ｐｂ／２０６Ｐｂ、ＳｍＮｄ、ＲｂＳｒ、４０Ａｒ／３９Ａｒ年代学方法对东秦岭陡岭群变质杂岩的形成时代、变质时期和构造归属进行了研究。结果表明：陡岭群变质杂岩形成于早元古代，年龄为２０００Ｍａ左右，在其形成后遭受了多期变质作用。片麻岩ＳｍＮｄ等时年龄１８７８±２５６Ｍａ（εＮｄ（ｔ）＝＋２．８±２．６）代表了ＳｍＮｄ同位素系统重新发生均一化作用的时间。主期变质作用发生在８３３±１７Ｍａ（角闪石４０Ａｒ／３９Ａｒ高温坪年龄）；另一期变质作用发生于４２２±１６Ｍａ（片麻岩Ｒｂ

Studies on Stalagmite Isotope Records of Paleoclimatictic Changes

More than two years'monitoring to the nowadays water_drop and carbonate sedimentation as well as the cave environment around a big stalagmite at the Panlongdong cave in Guilin has been conducted for the detaild study. It provides a basis for testing the balanced sedimentation of isotope and full exchange degree of 14 C.Meanwhile,the systematic and comprehensive studies with AMS 14 C,U series and stable isotope have been made along the axis cores of the stalagmites.A model has been presented for the climate changes in the past 36 000 as in Guilin area. The records of oxygen isotope of the stalagmites are basically consistent with the climate in-formation provided by the carbon isotope and the growth rate of stalagmite. They can also be compared with the results of the study of phenology in our country and the section of loess in northern China.