东天山双龙铜矿石英闪长岩锆石U-Pb定年、Hf同位素分析及对构造环境的制约

通过对新疆东天山雅满苏岛弧带双龙铜矿成岩地质特征、岩石地球化学特征及Hf同位素分析,认为赋矿岩体为一套形成于后碰撞环境下的准铝质高钾钙碱性岩石系列的石英闪长岩,LA-ICP-MS锆石U-Pb同位素年龄为(300.9±1.2)Ma。岩石地球化学显示,赋矿岩石具富集大离子亲石元素(LILE)K,Rb等及高场强元素(HFSE)Th,U,Zr和Hf,贫Nb,Ta,Ti,Sr,P特征,可能形成于后碰撞构造环境。石英闪长岩锆石176Hf/177Hf变化范围0.282949~0.283002,平均值0.282979,εHf(t)值为12.32~14.40,平均13.40,tDM2(Hf)为375~482Ma,平均429Ma,表明岩浆物源可能来自志留纪新生地壳的部分熔融。     

山东崔家峪玻璃用石英砂岩矿床地质特征及成因

崔家峪石英砂岩矿床赋存于下寒武系李官组,矿体呈层状,厚度5.2～15.50 m;矿石中砂结构,分选性好;矿石ω(SiO2)高达98.77%～98.98%,ω(Fe2O3)仅0.038%～0.045%,实属少见的超纯石英砂岩矿床.该矿床形成于温暖潮湿气候下的稳定大陆壳边缘滨海环境,石英直接来源于震旦系土门群砂岩,矿床是剥蚀-沉积多个旋回不断分选富集的结果.研究该矿床地质特征和成因具有地质和找矿指导意义.     

北美五大湖区晚更新世劳伦泰德冰盖演化年代学综述及石英光释光测年的初步尝试

北美五大湖区的安大略湖北岸Don Valley Brickyard、Scarborough Bluffs、Bowmanville Bluffs剖面共同构成了北美东北部最长也是最厚的陆地第四纪沉积记录, 较完整地记录了晚更新世劳伦泰德冰盖(the Laurentide Ice Sheet)的演化. 晚更新世劳伦泰德冰盖演化的重建有赖于这些经典剖面中重要沉积地层单元的准确年代学控制. 传统的地层年代学主要是依靠少量¹⁴C年代, 将主要的混杂堆积单元(diamicton)解释为气候变冷环境下的冰川扩张, 并与指示全球冰量变化的深海氧同位素曲线一一比对建立起来的. 这样建立起来的年代学存在很大的不确定性. 20世纪80-90年代的少量热释光年代也不相吻合, 最近的13个长石红外释光定年则只集中于Bowmanville Bluffs的一个分层, 并未建立整个剖面的地层年代学, 使这些经典沉积剖面的年代学一直没有得到系统的建立. 应用石英光释光SAR-SGC法测试了Bowmanville Bluffs剖面Glaciofluvial Sand单元的2个冰水沉积样品, 年代结果分别为(41.6±3.8) ka、(48.1±4.4) ka, 分析表明这一年代结果偏老, 石英颗粒可能晒褪不完全. 由于大测片无法识别晒褪不完全的颗粒, 因此, 测试更多的剖面序列的光释光年代并尝试采用粗颗粒小测片或单颗粒技术解决样品颗粒晒褪不完全的问题将是必要的.     

湖北狮子立山锶(铅锌)矿区石英闪长玢岩锆石SHRIMP U-Pb定年及其意义

湖北狮子立山锶(铅锌)矿床是我国重要的超大型锶矿床之一,产出于鄂东矿集区北部铁山岩体东缘的狮子立山岩体(主要为石英闪长玢岩)与三叠纪蒸发岩地层(嘉陵江组)的接触带或附近。本文对矿区内的石英闪长玢岩与成矿作用之间的关系和该岩体的年代学开展了详细的研究工作。结果表明,狮子立山岩体与锶矿成矿作用可能存在密切的联系,矿床中的部分Sr可能来自于石英闪长玢岩的强烈蚀变。锆石SHRIMP U-Pb的定年工作得到2个石英闪长玢岩样品的形成时代分别为138.6±0.8Ma和138.9±1.2Ma,二者在误差范围内基本一致,这些数据与前人获得的铁山岩体的成岩时代基本一致,暗示本次测得的石英闪长玢岩的样品年龄可靠性较高,且很可能与铁山岩体是同一地质背景下的产物,即形成于区域晚侏罗-早白垩世岩石圈由挤压到伸展的转换环境。狮子立山岩体的侵位地层及矿床中硫同位素组成的特征与程潮和金山店矽卡岩型铁矿具有明显的相似性,暗示在狮子立山矿床附近具有寻找矽卡岩型铁矿床的潜力。     

Influence of Changes in the Prevailing Synoptic Conditions on the Response of Aerosol Characteristics to Land- and Sea-Breeze Circulations at a Coastal Station

The changes in the response of near surfaceaerosol properties to land- and sea-breezecirculations, associated with the changes in the prevailing synoptic meteorological conditions, are examined for a tropical coastal station. Aerosol properties are nearly similar in both the breeze regimes (land and sea) during seasons of marine airmass while they are distinct during seasons of continental airmass. As the prevailing winds shift from continental to marine and the ambient weather changes from winter conditions to the humid monsoon season, the submicron mode, which dominated the aerosol mass-size distribution, is largely suppressed and the dominance of the super micron mode increases. During periods of continental air mass (winter), the aerosol loading is significantly higher in the land-breeze regime, (particularly in the submicron range) but as the winds shift to marine, the loading initially becomes insensitive to the breeze regimes and later becomes higher in the sea-breeze regime, particularly in the super micron range.     

石英变形纹NDA技术在控矿构造研究中的应用

本文以辽宁兰家沟钼矿床为例，说明了石英变形纹数字动力学分析（ＮＤＡ）技术的原理、方法及其在控矿构造研究中的应用。在弱变形情况下，该技术能够较为快速、定量地提供控矿古构造应力场的有关信息。应用效果与构造岩结构及定向薄片产状有很大关系。     

A natural example of crystal-plastic deformation enhancing the incorporation of water into quartz

Water content of quartz in and around a greenschist facies mylonitic shear zone located in the western Adirondacks was analyzed by micro-FTIR spectroscopy. The shear zone is within a pegmatitic dike, which cuts across a granitic gneiss. The thickness of the shear zone varies along strike from 15 cm wide and encompassing all of the pegmatite dike at its northern most exposure to 5 cm wide approximately 10 m south, along strike. Microstructures, including quartz ribbons and recrystallized grains, indicate quartz and feldspar within the mylonite underwent dislocation creep. Infrared spectral analysis was carried out using a Nicolet micro-FTIR on mylonitic quartz ribbons, pegmatitic quartz and gneissic quartz. A small aperture size (56 μm by 50 μm) for the IR beam allowed optically clear regions of the quartz grains to be analyzed without any contribution from grain boundaries. The smallest dimension of the quartz ribbons is 0.3 mm, whereas the pegmatitic quartz has a grain size of 3 to 5 cm. Results show mylonitic quartz ribbons contain the most water (320 H:10⁶ Si average, range of 50 to 1120 H:10⁶ Si); pegmatite quartz contains much less water (30 H:10⁶ Si average, range of 20–40 H:10⁶ Si) and the gneissic quartz contained an intermediate amount (200 H:10⁶ Si average, range of 20 to 870 H:10⁶ Si). These data indicate that water was preferentially incorporated into the deformed quartz ribbons.     

Structural controls on orogenic gold mineralisation in the Klondike goldfield,Canada

The Klondike Schist that forms the basement rocks for the famous Klondike placer goldfield was emplaced as km-scale thrust slices in Early Jurassic time, along with some thin (10 to 30 m-scale) slices of greenstone and ultramafic rocks. Permian metamorphic fabrics in the schists were deformed during thrust emplacement by structures formed as the rocks passed through the brittle–ductile transition. Early-formed thrust-related structures were almost-pervasive recumbent folds that affected both the schist and greenstone/ultramafic slices and imposed a spaced cleavage with minor recrystallisation of micas. These structures gave way to shallow-dipping phacoidal cleavage near (within <100 m of) thrust structures. Thrust-related structures have been overprinted locally by well-defined steeply dipping reverse fault-fold zones, and associated upright folding on regional (km) to mesoscopic (m) scales. The fold-fault zones occur as two orthogonal sets of structures oriented NW to N and NE to E. Some of these steeply dipping fault zones have been reactivated by Late Cretaceous normal faulting. Orogenic (mesothermal) gold-bearing veins were emplaced in local sites of extension during or after formation of the compressional fault-fold zones and before normal fault reactivation. Over 400 veins (m to cm-scale) observed in this study imply a general NW strike for mineralised structures (W to N), but with a broad scatter of orientations. Vein emplacement was controlled principally by fold axial surfaces of kink folds of the fault-fold generation. However, some other local extension sites have opened along preexisting structures to host veins locally, including metamorphic foliation and spaced cleavage planes. In addition, irregular extensional fractures with no obvious structural control host some veins. The Klondike mineralised veins formed as swarms with broad regional structural control, but represent relatively diffuse mineralised zones, with numerous scattered small veins, compared to most orogenic vein systems. These diffuse vein swarms appear to be sufficient sources for the rich and geographically localised placer gold deposits that formed in overlying gravels during erosion of the Klondike Schist basement.     

汉寿高仑山石英岩矿床地质特征及开发前景

高仑山沉积-变质石英岩矿床产于岩坝桥岩体北东外蚀变带,是省内新型硅石矿床类型。它系灯影组硅质岩受岩体热液蚀变形成。矿石矿物成分98—99％为石英。大型矿床规模。原矿经破碎水洗法选矿后,精矿含SiO_2 99.16％,质量达优质型砂。目前产品暂应用于铸造行业,经数家精铸厂试验,能铸出合格钢铸件。该矿床开采条件优越,潜在经济价值巨大,开发利用前景广阔。