广东河台金矿床矿物特征对成矿环境的制约

位于高要市境内的河台金矿床是目前广东省最大的金矿床,被普遍认为是韧性剪切带型金矿床。为了进一步认识金矿床的成矿环境,对采自河台矿区高村矿段的矿石进行了详细的研究,利用电子探针(EPMA)分析了矿石中毒砂、绿泥石和闪锌矿等矿物的成分。通过矿物温度计计算,毒砂的形成温度在330℃左右,绿泥石的形成温度集中在230~250℃之间,闪锌矿的形成温度在205~230℃之间,可能分别代表成矿早、中、晚期的温度;结合前人包裹体测试结果,推测河台金矿床成矿温度可能在205~250℃之间,属于中低温热液矿床。而糜棱岩的形成温度可能在300~500℃之间,明显高于金矿床的形成温度,因此,河台金矿床可能是动力变质期形成的糜棱岩带在热液期又发生脆性变形,并伴随含矿热液活动,最终导致成矿。在成矿过程中,绿泥石和闪锌矿是随着温度降低而相继连续产出的。在此过程中硫逸度也在不断降低,表现出比较宽泛的特征,lgf(S2)可能介于-20~-1,lgf(O2)可能介于-50~-30。     

加强地质科技项目管理 助力新时期找矿突破

找矿突破战略行动自实施以来,取得了一系列成果,重要和紧缺矿种新增资源储量保持较快增长,国内矿产资源保障能力增强。通过近5年的探索和努力,找矿效果显著,新发现一批重要矿产地,新增一批矿产资源,发现并查明了大湖塘钨矿床、大营铀矿床、沙坪沟钼矿床等一批世界级矿床,西藏甲玛铜矿床、多龙铜矿床、青海夏日哈木镍矿床等一批超大型矿床,并有望形成西藏扎西康铅锌矿床、贵州铜仁锰矿床等一批新的资源基地,对于立足国内资源保障,优化矿产资源格局具有重要的推动作用。2015年,全国地质勘查投资总额为899.3亿元,新发现主要固体矿产大中型矿产地144处。     

黔东松桃盘石-盘信地区铅锌矿成矿地质条件分析

黔东松桃盘石-盘信地区及其邻区位于雪峰山西缘。研究区经受了加里东期、印支期、燕山期等多期构造作用的改造,构造变形极为复杂（金宠,2010;李三忠等,2011）。近年来,位于研究区相邻的湖南花垣发现了超大型铅锌矿床而引起人们的极大关注（杨绍祥等,2007;周云等,2011）,黔东铅锌成矿区作为川、滇、黔成矿带和湘西-鄂西成矿带的交汇部分,且毗邻湘西花垣铅锌矿集区,已发现有嗅脑、粑粑寨、康金、小红岩、团塘、老屋场等铅锌矿点,但这些矿点普遍规模小、矿石品位底,经济价值较小（图1）。尤其值得注意的是：研究区与花垣相邻,两者有相同或相近的地质背景与成矿条件, 因而该区找矿潜力较大。本文即对该区铅锌矿成矿地质条件作出简要分析。     

A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation,Alberta, Canada

A recently discovered articulated partial skeleton of Ornithomimus from the Upper Cretaceous Dinosaur Park Formation of Alberta, Canada is remarkable in the extent and quality of preservation of integumentary structures including feathers. It is the first ornithomimid to preserve a tail bearing extensive plumaceous feathers that are slightly more elongate in comparison to those present on the remainder of the body. However, the underside of the tail and the hind limb distal to the middle of the femur appear devoid of plumage. Overall, the plumage pattern in Ornithomimus is similar to that of Struthio camelus (ostrich) and other large palaeognaths, indicating a probable function in thermoregulation. The specimen also preserves the body outline around the legs, including a skin contour anterior to the femur, analogous to skin webs in extant birds. Whereas the knee web of birds bridges the knee to the abdomen, in Ornithomimus it spans from the mid-femoral shaft to the abdomen, and is herein referred to as an anterior femoral web. This is the first report of such soft tissue structures in non-avian theropods. It may indicate that the resting position of the femur was positioned more anteroventrally in ornithomimids than in most theropods, and in that sense may have been transitional to the situation in modern birds.     

吉木萨尔凹陷芦草沟组烃源岩评价及页岩油富集条件探讨

准噶尔盆地吉木萨尔凹陷芦草沟组为一套优质陆相烃源岩, 是我国当前页岩油气研究的热点地区之一.基于吉木萨尔凹陷18口井芦草沟组约为580 m岩心观察、薄片观察、地球化学测试等数据, 对芦草沟组烃源岩岩石类型、地球化学特征等方面开展了研究与评价, 结果表明: 1)芦草沟组烃源岩整体上为优质烃源岩, 且以Ⅰ-Ⅱ型有机质类型为主, 处于低熟至成熟阶段; 2)烃源岩主要划分为5种类型, 包括纯页岩、白云质页岩、纯泥岩, 白云质泥岩和粉砂质泥岩, 其有机质类型和丰度存在一定差异.综合研究得出, 吉木萨尔凹陷芦草沟组优质有效烃源岩的有机质丰度下限值为2.0%, 并认为TOC≥2.0%的烃源岩段也是该区页岩油发育的有利层段.     

Dissolution-precipitation reactions controlling fast formation of dolomite under hydrothermal conditions

In laboratory experiments, the precipitation of dolomite at ambient temperature is virtually impossible due to strong solvation shells of magnesium ions in aqueous media and probably also due to the existence of a more intrinsic crystallization barrier that prevents the formation of long-range ordered crystallographic structures at ambient surface conditions. Conversely, dolomite can easily form at high temperature (>100 °C), but its precipitation and growth requires several days or weeks depending on experimental conditions. In the present study, experiments were performed to assess how a single heat-ageing step promotes the formation of dolomite under high-carbonate alkaline conditions via dissolution-precipitation reactions. This reaction pathway is relevant for the so-called hydrothermal dolomite frequently observed in carbonate platforms, but still ill-defined and understood. Our precipitation route is summarized by two main sequential reactions: (1) precipitation of Mg-calcite at low temperature (∼20 °C) by aqueous carbonation of synthetic portlandite (Ca(OH)₂) in a highly alkaline medium (1 M of NaOH and 1 M of MgCl₂), leading to precipitation of oriented nanoparticles of low- and high-Mg calcite (∼79 wt%) coexisting with aragonite (∼18 wt%) and brucite (∼3 wt%) after 24 h; (2) fast dolomitization process starting from 1 h of reaction by a single heat-ageing step from ∼20 to 200, 250 and 300 °C. Here, the Mg-calcite acts as a precursor that lowers the overall kinetics barrier for dolomite formation. Moreover, it is an important component in some bio-minerals (e.g. corals and seashells). Quantitative Rietveld refinements of XRD patterns, FESEM observations and FTIR measurements on the sequentially collected samples suggest fast dolomite precipitation coupled with dissolution of transient mineral phases such as low-Mg calcite (Mg < 4 mol%), high-Mg calcite (Mg > 4 mol%), proto-dolomite (or disordered dolomite; Mg > 40 mol%) and Ca-magnesite. In this case, the dolomite formation rate and the time-dependent mineral composition strongly depend on reaction temperature. For example, high-purity dolomitic material (87 wt% of dolomite mixed with 13 wt% of magnesite) was obtained at 300 °C after 48 h of reaction. Conversely, a lower proportion of dolomite (37 wt%), mixed with proto-dolomite (43 wt%), Ca-magnesite (16 wt%) and high-Mg calcite (4 wt%), was obtained at 200 °C after 72 h. The present experiments provide an additional mechanism for the massive dolomite formation in sedimentary environments (ex. deep sea organic-rich carbonate-sediments) if such sediments are subjected to significant temperature variations, for example by hot fluid circulations related to volcanic activity. In such systems, organic degradation increases the carbonate alkalinity (HCO₃⁻) necessary to induce the dolomitization process at low and high temperature.     

柴达木盆地鱼卡凹陷侏罗系泥页岩地球化学特征及储集条件——以柴页1井为例

柴达木盆地北缘鱼卡凹陷发育的侏罗系泥页岩是中国北方陆相页岩气勘探的目的层系之一。为进一步明确鱼卡凹陷侏罗系泥页岩地化-储集条件,系统采集了柴页1井泥页岩岩心样品,开展了总有机碳、热解氢指数、镜质体反射率、孔隙度和渗透率、扫描电镜、矿物组成及等温吸附特征实验分析。结果表明,柴页1井中侏罗统大煤沟组泥页岩有机质类型和成熟度利于有机质孔隙发育,较高的总有机碳含量利于页岩气富集;粘土矿物的存在虽然抑制了泥页岩微孔隙的发育,但对其吸附能力有促进作用。鱼卡凹陷具有良好的页岩气生成和储集条件,是页岩气勘探的有利地区。     

辽河盆地大民屯凹陷古近系沙河街组页岩气成藏地质条件研究

辽河盆地大民屯凹陷厚层暗色富有机质泥页岩的沉积特征研究和地球化学数据分析结果表明,大民屯古近系凹陷古近系沙河街组发育湖泊和扇三角洲沉积。在扇三角洲中的沼泽地带,发育富有机质的碳质泥岩。暗色泥岩主要产生于半深湖-深湖环境中,具有厚度大、连续性强、分布广的特点。泥岩中的干酪根类型主要以腐泥腐殖质型(II2)和腐殖型(III)为主,利于产气。有机质成熟度(Ro)平均为0.8%~1.3%,有机质处于低熟-成熟阶段。TOC平均为3%~8.46%,有机质丰度较高。脆性矿物总量达到29.0%~51.7%,有利于页岩气的开采。页岩气类型主要为热成因页岩气和生物化学成因页岩气。在页岩气成藏的地质因素分析基础上,综合研究认为,荣胜堡洼陷和三台子洼陷是沙河街组页岩气富集的有利区域。     

黄河上游甘南地区地质灾害形成条件及防治对策

作为"黄河蓄水池"的黄河上游甘南地区,为整个黄河流域重要的水源补给区,区域内的地质环境条件直接影响着黄河流域生态安全及经济社会的可持续发展。目前,区内发育地质灾害点346处,威胁人口6.79万人,财产21.42亿元,已成为区内威胁较为严重的环境地质问题之一。本文通过对地质灾害形成条件的调查分析,在充分了解灾害特征的基础上,有针对性的提出地质灾害治理的防治对策,为地方防灾减灾工作提供借鉴和参考。