五台山新太古代块状硫化物矿床成矿作用研究——海底喷流沉积成因显微构造证据

在五台山金岗库新太古代块状硫化物矿床发现了一些多孔状黄铁矿石标本,经过详细的显微构造鉴别和相关的电子探针分析,发现其中保留的一些特征性显微结构(胶状结构、通道构造、分带构造及淬火构造等)与现代海底硫化物黑烟囱结构构造非常类似,初步得出这些标本为新太古代海底黑烟囱的残片,显示了该矿床黑烟囱模式的海底喷流成因机制。     

青岛马山-王哥庄断裂带构造活动性分析

本文从构造地质学、地震学和地球动力学的角度出发,论述了青岛及邻区的地质构造背景,阐述了青岛马山—王哥庄断裂带的构造活动特征,分析了青岛地区的地震活动性.通过分析2003年6月和2004年11月的崂山震群活动特征,进一步确定了马山—王哥庄断裂带的构造活动性.受来自南黄海的区域构造应力作用,该断裂带尤其是其东南段表现出较强的构造活动性,具有引发有感乃至中等地震的可能性.     

龙首山-北大山北部的属性——来自海森楚鲁片麻岩锆石U-Pb年龄和Hf同位素的约束

阿拉善北大山西北部地区出露少量原属"龙首山岩群"的前寒武纪岩石,其形成时代和同位素特征对于了解该地区的基底性质和探讨阿拉善北部构造格架具有重要意义。本文对北大山西北部海森楚鲁地区出露的片麻岩开展了详细的岩石学、锆石U-Pb年代学和Hf同位素研究,并对其构造意义进行了初步探讨。海森楚鲁片麻岩为一套具有片麻状构造的长英质正片麻岩。锆石核部的LA-ICP MS分析结果显示,207Pb/206Pb年龄相对集中,并在U-Pb谐和图上获得了1 408±29 Ma(MSWD=13)的上交点年龄,表明海森楚鲁片麻岩的原岩形成于～1. 4 Ga。海森楚鲁片麻岩的锆石Hf同位素分析结果显示,锆石εHf(t)值变化范围为-4. 38～+6. 68,二阶段模式年龄为2 091～1 624Ma,反映了片麻岩原岩岩浆可能来自相对年轻的地壳物质。结合前人研究成果,认为龙首山-北大山北部出露的前寒武纪岩石主要形成于中元古代及以后,而不是以往认识的中太古代-古元古代;龙首山-北大山北部可能不是阿拉善地块的组成部分。     

2001年9月至2002年11月峨眉山降雨化学组成动态变化

2001年9月初在峨眉山从金顶气象站(海拔3070m)到成都理工大学实习基地(海拔486m)大约每隔100m放置了一个雨水收集桶,共25个雨水采集点,并从2001年9月至今每月收集雨水分析。本文选取了2001年9月至2002年11月在25个雨水采集点采集的雨水样的阴阳离子,pH,EC(电导度)等分析结果进行研究,归纳了pH,PAi,EC以及主要的阴阳离子的变化规律,即它们的变化基本受季节变化以及高程的控制。     

神农架石笋氧同位素的海拔效应

作为古气候代用指标,石笋氧同位素为亚洲季风演化研究提供了一系列可靠的证据。然而,关于石笋氧同位素指示的气候意义一直存在争论。本文选取了位于神农架地区海拔1250～2250m的黑龙洞、青天洞和三宝洞3个洞穴进行对比分析,发现不同海拔洞穴石笋δ18O在波动形式上相同,但绝对值存在约-0.1‰/100m的系统差,而大气降水的在该地的海拔效应约为-0.2‰/100m。为此,我们认为,石笋δ18O除了受季风降雨的影响外,不同海拔的温度梯度也对石笋δ18O具有较大的贡献。结合洞穴年均温度,初步估算石笋δ18O的温度效应约为-0.25‰/℃,与O’Neil的同位素平衡分馏计算结果相同。      

In situ cosmogenic Be in olivines and pyroxenes

This study proposes an efficient new cleaning procedure for measuring in situ cosmogenic ¹⁰Be in olivines and pyroxenes. This chemical routine is specially designed to decontaminate the abundant meteoric ¹⁰Be from these minerals. The method was tested on mafic minerals from basaltic flows of Mt. Etna volcano and from Hawaiian flows and moraines. A sequential dissolution test shows that ¹⁰Be concentrations decrease with the number of cleaning steps until reaching a constant value. This is a necessary condition to demonstrate the efficiency of the method in properly decontaminating samples of meteoric ¹⁰Be. Moreover, cross-calibration with cosmogenic ³He measured within the same samples yielded a sea level high-latitude production rate of 4.5±0.4 at g⁻¹ a⁻¹ for cosmogenic ¹⁰Be in mafic minerals. This rate is within 1σ uncertainty of empirically or model-derived rates for ¹⁰Be on the same targets. Such concordance supports the consistency of the new method.     

山区岩溶作用对土地利用方式的响应——以金佛山碧潭泉和水房泉两区岩溶系统为例

不同的土地利用方式可使土地理化性质产生一系列的变化和差异,从而影响到岩溶作用的方向和强度。通过野外溶蚀试片实验法,对金佛山典型岩溶区碧潭泉和水房泉两泉域岩溶生态系统的5种典型土地利用方式下的土壤溶蚀速率进行雨季短时间尺度变化的野外观测。2006年7月中旬开始,重庆地区罕遇43天高温无雨的特殊天气,测试结果表明不同土地利用方式甚至同一土地利用方式下不同海拔的岩溶区石灰岩试片溶蚀速率都存在较大差异,碧潭泉域雨季绝对溶蚀量仅为水房泉域的13.3%,6个测试点土下溶蚀量由大到小依次为水房泉竹林地、水房泉林地、水房泉草地、碧潭泉林地、碧潭泉灌草丛、碧潭泉耕地。在研究时间内降雨量、温度和土壤CaCO3含量差异的基础上,金佛山两泉域岩溶作用主要有两个控制因素:土壤CO2浓度、土壤有机质。     

Clustering properties of Etna seismicity during 1981–1991

Space and time clustering properties ofseismic activity, affecting Etna Volcano (Italy)during 1981–1991, are investigated by fractaldimension analysis. Very interesting volcanic andseismic activity occurred within this time interval.Temporal evolution of the time fractal dimension D _t calculated on a moving window, revealscorrelation with the eruptive processes at differenttime scales confirming results obtained for a differenttime span (De Rubeis et al., 1997). Spatial fractaldimension D _s shows to be negativelycorrelated with the time fractal dimension D _t, suggesting a peculiar dynamic patternassociated with volcanic processes.     

Textual Research on the July 7,1590 A. D. Southeastern Yongjing Earthquake in Gansu Province

According to historical records,in July of 1590 A.D.,a destructive earthquake occurred near Lintao county in Gansu Province,in which "… city walls and houses collapsed,and countless people and domestic animals were killed".In the same month,Binggou town in eastern Qinghai Province(now northeastern Ledu county),was also damaged by an earthquake.These two earthquakes were listed as two different cases in the published earthquake catalogues,recorded separately as the Lintao M_S5.5 earthquake with epicentral intensity Ⅶ in Gansu Province and the Ledu M_S5.0 earthquake with epicentral intensity Ⅵ in Qinghai Province.However,based on comprehensive analysis of research on historical records and field investigations,it is concluded in this paper that these two earthquakes could be the same one with magnitude 6.5 and epicentral intensity Ⅷ～Ⅸ.Its epicenter was in the Maxian Mt.,which is located in southeastern Yongjing and its seismogenic structure might be the mid-western segments of the north fringe fault zone of Maxian Mt.of Lanzhou.