河南渑池仰韶人遗址区黄土冲沟阶地的释光测年研究

地貌变迁与古人类活动的关系一直是地理学研究的一个重要科学问题。仰韶文化是黄河流域最为重要的新石器人类 文明之一,文章以河南渑池仰韶遗址区内西沟冲沟为研究对象,尝试建立仰韶人类活动与遗址区内冲沟地貌形成的先后关 系。渑池仰韶遗址区地处黄土高原东南缘黄土堆积区,文章利用释光测年方法测定了西沟冲沟阶地上覆堆积黄土的年代, 粗略重建了阶地形成的时间为大约距今3万年和12万年前,分别对应深海氧同位素（MIS） 3阶段和5阶段。而该时期渑池 仰韶区域尚无古人类活动记录,所以释光测年结果证明仰韶遗址区内的冲沟完全是自然成因的,与遗址区仰韶人的地表活 动无关。     

北祁连造山带东段老虎山石英闪长岩成因及其地质意义

以北祁连造山带东段老虎山石英闪长岩体为研究对象,进行了锆石U-Pb年龄及全岩元素与Sr-Nd同位素组成的系统 测定,据此探讨了岩石的成因及其对北祁连构造演化的启示。锆石LA-ICP-MS U-Pb定年结果表明,石英闪长岩体的形成 年龄为440 Ma。岩石具有亚碱、准铝以及贫钙、镁、铁的特征,碱铝指数（AKI值） 均低于0.85,铝饱和指数（A/NKC 值） 多小于1.0,属钙碱性I型花岗岩类岩石。在稀土和微量元素组成上,岩石富集轻稀土和大离子亲石元素（如Rb、Cs、 Th和U）,亏损高场强元素（如Nb和Ta）,显示弧岩浆岩的地球化学特征。岩体具有相对均一的Sr-Nd同位素组成,初始Sr同 位素值为0.7058~0.7071,εNd(t)值为-1.06~-0.31。综合分析表明,老虎山石英闪长岩应起源于玄武质下地壳物质的部分熔 融,并在成岩过程中有少量幔源物质的混入。对区内火成岩地质地球化学特征与产出背景的全面分析,表明受北祁连洋俯 冲及随后岛弧与祁连—柴达木陆块碰撞拼贴影响,弧后盆地的北向俯冲消减作用可能是诱发民乐窑沟和老虎山弧岩浆岩以 及导致毛藏寺—老虎山花岗岩带内埃达克质岩石侵位的基本动力机制。     

山西青尖坡石英二长岩锆石U-Pb年龄及其地质意义

通过对华北克拉通北缘青尖坡石英二长岩锆石U-Pb同位素年龄分析,并结合相关主量和稀土元素数据探讨其地质意义。研究表明,石英二长岩LA-ICP-MS锆石U-Pb同位素年龄为241.1±1.7Ma,为早中三叠世岩浆活动的产物。岩石具有富K、Na、Si、Al,贫Mg、Ca、Ti等特征,为高钾碱性钾玄岩系列,属于过铝质花岗岩类;轻稀土元素相对富集,重稀土元素相对亏损,具有稳定的弱负Eu异常。总体为I型花岗岩成因,但兼具S型花岗岩的特征。青尖坡石英二长岩为中下地壳部分熔融成因,有地幔物质参与,为华北克拉通北缘三叠纪碱性岩带的组成部分,形成于晚造山-造山后的伸展构造环境。     

新疆伊吾地区晚石炭世石英闪长岩LA-ICP-MS锆石U-Pb年龄及其地质意义

新疆伊吾地区晚石炭世侵入岩产于天山-兴蒙造山系谢米斯台-库兰卡兹干古生代复合岛弧带的东段。用LA-ICP-MS技术测得伊吾地区石英闪长岩中锆石~(206)Pb/~(238)U年龄为312.4±1.5Ma(MSWD=0.18,n=30),属晚石炭世。岩石化学资料表明,伊吾地区晚石炭世侵入岩为准铝质高钾钙碱性岩系,轻稀土元素富集,重稀土元素平坦,具中等程度的负Eu异常。微量元素中富集轻稀土元素及Ba、Th等大离子亲石元素,而相对亏损Nb、Ti、P元素,P元素较强亏损可能与磷灰石分离结晶作用有关,元素地球化学组成指示其与大陆地壳物质具有明显的亲缘性;以上资料揭示,伊吾地区在晚石炭世已经处于后碰撞构造环境。     

阳原台石英水平摆倾斜仪数字化改造

2003年10月由张家口中心地震台和中国地震局地球物理研究所地震仪器厂,共同对阳原台SQ-70型石英摆倾斜仪进行了数字化改造。改造后的仪器,经过6个月的运行,目前,该仪器运行良好,产出资料稳定、可靠、精度高。     

An X-ray excited optical luminescence study of a zoned quartz crystal from an emerald-bearing quartz vein,Hiddenite, North Carolina,USA

The optical luminescence excited with synchrotron radiation along a preferential orientation of a quartz crystal has been investigated. It is found that the crystal is composed of two distinct regions, only one of which luminesces upon X-ray excitation. This luminescence is generally uniform and exhibits emission bands in the blue (470 nm with a shoulder at 522 nm) and in the UV (340 nm) regions of the spectrum. The branching ratio for the intensity of these bands is sensitive to the excitation energy across the Si K-edge. XANES spectra collected by partial luminescence yield (PLY) suggest that both emission bands originate from the de-excitation of Si atoms in the quartz. The possible defect sites within the crystal structure that could account for the observed luminescence are investigated and discussed. Additional experiments are proposed to verify this assignment of the optical emission bands.     

四川省青川玉石矿的地质特征及其找矿意义

青川石英质玉是近年在四川省发现的新玉石矿。玉石矿体赋存于新元古界通木梁群太阳坪组云母石英片岩中。玉石的矿物成分主要为石英、铬云母、铬绢云母,具显微细粒粒状、片状变晶结构,片状、条带状构造。玉石种类分为绿色和白绿色,具油脂光泽;矿体规模大、块度好,玉石品质佳、可加工性强,可制作手镯、摆件、挂件、雕件等。根据野外地质工作判断,青川石英质玉属于区域变质成因,青川玉石矿的发现填补了四川石英质玉的空白,对丰富区域成矿系列和拓展区域玉石矿找矿方向具有重要意义。     

石英脉型钨矿成矿研究进展

我国钨矿的储量、产量、消费量和出口量均处于全球领先地位,尤其是石英脉型钨矿床研究成果最为丰富。本文通过大量查阅国内外有关石英脉型钨矿的文献资料,对石英脉型钨矿的成矿研究成果和观点进行综合评述。石英脉型钨矿在我国各个成矿带均有分布,其空间分布和区域构造单元息息相关,所处的区域构造活动一般都很强烈,经历多次叠加构造运动。钨矿床产在震旦寒武系地层中,特别是在寒武系地层最多。成矿物质主要来源是岩浆热液,岩浆活动频繁为成矿热液的形成创造了必要的前提条件,但也有部分成矿物质源于围岩。石英脉型钨矿成矿模式以"五层楼+地下室"成矿模式最具影响力和实际意义,开创了模式找矿的先河。     

Cambrian wave‐dominated tidal‐flat deposits,central Wisconsin,USA

In central Wisconsin, Cambrian strata of the Elk Mound Group record deposition on open‐coast, wave‐dominated tidal flats. Mature, medium‐grained quartz arenite is dominated by parallel‐bedding with upper‐flow regime parallel‐lamination, deposited during high‐energy storms that also produced three‐dimensional bedforms on the flats. Abundant wave ripples were produced as storms waned or during fair weather, in water depths ≤2 m. Indicators of variably shallow water (washout structures and stranded cnidarian medusae) and subaerial exposure (adhesion marks, rain‐drop impressions and desiccation cracks, including cracked medusae) are abundant. Parallel‐bedded facies preserve a Cruziana ichnofacies, similar to other Cambrian tidal‐flat deposits. Flats were dissected by small, mainly straight channels, the floors of which were grazed intensely by molluscs. Most channels were ephemeral but some developed low levées, point bars and cut‐banks, probably reflecting stabilization by abundant microbial mats and biofilms. Channels were filled with trough cross‐bedding that is interpreted to have been produced mainly during storm runoff. The strata resemble deposits of open‐coast, wave‐dominated tidal flats on the east coast of India and west coast of Korea. Ancient wave‐dominated and open‐coast tidal flats documented to date appear to have been limited to mud‐rich strata with ‘classic’ tidal indicators such as flaser bedding and tidal bundles. The Cambrian (Miaolingian to early Furongian) Elk Mound Group demonstrates that sandy, wave‐dominated tidal flats also can be recognized in the stratigraphic record.     

敦煌金滩子金矿床地质特征及找矿前景分析

敦煌金滩子金矿床系20世纪70年代初,在区调工作中检查古代采矿遗迹时发现,80年代开展过普查,经2014~2015年详查提交的一处中型金矿床。矿区由梭子山、八卦图和金滩子3个矿段组成。金矿化受断裂破碎带控制,加里东晚期石英闪长岩为八卦图和金滩子矿段石英脉型金矿的赋矿岩石,华力西中期二长花岗岩为梭子山矿段蚀变岩型金矿的赋矿岩石。目前控制主矿体长151~320 m、斜深155~350 m、矿体平均品位7.61×10~(-6)~17.94×10~(-6),矿体延伸较稳定,金品位较高。黄铁矿、褐铁矿、石英、方解石为主要载体矿物。据对金滩子金矿各矿段深部矿化特点及走向上控矿因素的分析,认为该矿床具有较好的找矿前景。