珠江口盆地珠一坳陷古近系高自然伽马砂岩形成机制及油气地质意义

运用放射性元素寻找油气是一种非常规油气勘探手段。近年来,在珠江口盆地珠一坳陷富烃凹陷周边古近系钻遇高自然伽马(GR)砂岩,其GR值(100~300 API)甚至大于同区泥岩的GR值(100~200 API)。为了弄清该特殊现象背后的地质意义,对珠江口盆地珠一坳陷古近系高自然伽马砂岩开展了铀(U)、钍(Th)、钾(K)等3种元素含量与GR值的相关趋势线分析,从井震特征、岩性特征及矿物成分特征等入手分析了砂岩GR值增高的主要原因及成因机制,探讨了放射性元素聚集的条件、运移通道、驱动力以及油气意义。结果表明:西江、惠州地区由U含量增高导致砂岩GR值偏高,恩平、番禺地区由K,Th含量增高导致砂岩GR值偏高;砂岩GR值增高有两大成因机制,一是地下流体带来的放射性元素离子U4+在氧化-还原面处富集后导致地层GR值偏高,这种特殊现象说明在具有连通基底大断裂旁的圈闭中,U4+的富集指示了曾经油气的存在,证实了研究区油气运移通道的有效性,对于油气藏的预测有着非常重要的指导性意义,二是地表流体带来的含放射性元素的矿物大量沉积后导致地层GR值偏高,含放射性元素矿物性质不稳定,可指示近源供给的存在,对于判断物源及沉积环境有着非常重要的意义。该研究成果为预测研究区油气成藏有利区带提供了依据。     

矿床成因对硫化铜矿选矿工艺流程的影响

矿床成因决定了矿石类型、矿物共伴生组合、矿石结构与构造、矿物结晶程度等性质的差异,进而对矿石选别回收工艺产生影响。重点阐述了五种不同类型铜硫矿床的矿床特征和工艺矿物学特点,分析总结了各类型铜硫矿床的矿石结构构造、矿物组成等典型特征,并对不同类型铜硫矿床的典型特征对选矿工艺流程的影响进行了分析。通过研究初步探明了不同类型铜硫矿床物理化学特征及其影响浮选工艺流程的基本规律,可为不同类型铜硫矿选矿工艺流程的制定提供借鉴。     

Investigation and consideration on landslide zoning of multiple slope failures and debris flows of 2014 disaster in Hiroshima,Japan

This study was intended to examine the mechanism of multiple slope failures and debris flows that occurred in the outskirts of Hiroshima on 20th August 2014. A field survey of the mountain stream where large-scale damage was incurred was carried out and the characteristics of debris flows which made serious damages were investigated. There were five findings of this study. (1) The initiation of debris flows was not limited to thin and planar shallow failures, but also showed V or U shapes, where the eroded sediments seemed to be pushed out by artesian water, and the eroded depth exceeded several meters at many locations. (2) There were areas with high permeability, such as faults, fracture zones, and joints in Mt. Abusan. It is inferred that the constantly present groundwater in these areas became artesian water because of a large amount of rainfall in upstream locations. This quickly destabilized the slopes on a large scale. (3) There were at least three estimated debris flows at the mountain stream above Midorigaoka prefectural apartments in Yagi 3-Chome, where the worst damage occurred. The mountain stream near Abu-no-Sato housing complex also had multiple debris flows. Here, the secondary debris flow changed its flow path because of the presence of sediments from an earlier debris flow. (4) The actual volumes of flowed mass were much larger than that predicted at 11 of the 18 mountain streams in Midori-i and Yagi districts. The volume of the mass of five of these mountain streams was more than twice the estimated volume. It is necessary to modify the method of calculating the volume of unstable sediments in the mountain stream. (5) It was found that the devastating damage of buildings and human lives took place in the areas well beyond the special restricted zones. The present method to designate the special restricted zone must be revised considering such problems as the underestimation of the volume of unstable sediments, the assumptions of a single debris flow and on the direction of debris flow, and the effect of the difference on rock and soil types.     

升温和降温对无约束花岗岩热破裂的影响

温度变化会引起岩石内部矿物颗粒膨胀(收缩)不均匀,发生热破裂。温度变化有温度升高和降低两种作用方式,本文通过无约束花岗岩在升温和降温两种温度作用方式下的热破裂声发射实验研究,得到如下结论:(1)花岗岩升温过程中热破裂主要表现为中高温弹塑性破裂;降温过程中热破裂主要表现为中低温脆性破裂;(2)升、降温过程岩石的热破裂机理不同,升温过程主要为压缩热应力集中形成的压剪破裂,降温过程主要为局部拉应力集中造成的拉剪破坏;(3)根据声发射特征参数统计分析,同等温度范围内,岩石降温过程的热破裂声发射事件频度和强度均高于升温过程,约为2倍,降温过程的热破裂比升温过程剧烈。     

青海交通社矿区碱长花岗岩锆石U-Pb年龄、岩石地球化学特征及成因探讨

交通社铌钽矿床位于阿尔金造山带,是该带近年来新发现的一个铌钽矿床。论文以该矿床为研究对象,通过开展矿床地质特征调查,利用锆石U-Pb年代学、岩石地球化学特征,探讨了与成矿密切相关的碱长花岗岩岩石成因类型及成岩成矿构造背景,探讨矿床成因。锆石LA-ICP-MS U-Pb同位素定年龄结果显示,碱长花岗岩为(453±4) Ma,属于高钾钙碱性系列,岩浆演化程度高;碱长花岗岩构造背景为后碰撞构造环境。微量元素表现为轻重稀土分馏不明显,稀土元素配分图显示,轻重稀土均相对平坦,具有明显Eu/Eu~*负异常。结合主量元素判别,同位素分析得出成岩、成矿物质为壳幔混合源。通过对比研究,结合矿床大地构造环境、成矿条件,认为交通社铌钽矿床形成于晚奥陶世,碱长花岗岩的侵入导致矿床的形成。矿床类型初步定为碱性花岗岩型铌钽矿床。     

秘鲁绿山斑岩铜钼矿床地质特征及成因

绿山(Cerro Verde)斑岩铜钼矿床位于秘鲁南部古新世—始新世斑岩铜钼成矿带的北端。矿体赋存于前寒武系Charcani片麻岩、晚白垩世Yarabamba花岗闪长岩、古新世英安斑岩和石英电气石角砾岩中,热液蚀变由中心向外分别为:钾化带—泥化带—石英绢云母化带—青磐岩化带。矿床形成与板块俯冲有关的岛弧环境,受区域性印加普丘断裂控制,在古新世英安斑岩侵位,带来了大量成矿热液,形成了世界级的超大型斑岩铜钼矿床—绿山斑岩铜钼矿床。     

辽宁王营子钼矿地质特征及找矿标志

辽宁省朝阳市王营子钨钼矿位于努鲁儿虎山脉大青山东部,属辽西凌源—北票金成矿带高杖子—大庙—东五家子金成矿区中部,蝴蝶沟—王营子金钼多金属矿化带。研究区内地层、岩浆岩发育较好,构造未见明显特征。主要岩体以斑状花岗岩、似斑状花岗岩为主,矿体严格受似斑状花岗岩控制,富集于钾化似斑花岗岩中,矿脉与围岩无明显界线。基于野外实际勘查、成矿地质条件等的研究,认为王营子钼矿为细脉浸染型斑岩型钼矿,并总结了找矿标志。     

青海交通社铌钽矿床地质特征及控矿规律

交通社铌钽矿床是阿尔金造山带新发现的铌钽矿床。文章以该矿床为研究对象,通过开展矿床地质特征调查,研究总结矿床地质特征及控矿规律。交通社铌钽矿区划分的4条矿化带,其中Ⅰ、Ⅱ、Ⅳ矿带均为金矿;Ⅲ矿带为铌钽矿,圈出铌钽矿体6条,长200~2640m,厚度为4. 87~12. 35 m,品位(Nb2O5) 0. 016%~0. 034%,矿体受碱长花岗岩控制。矿化蚀变主要有:矽卡岩化、硅化、碳酸盐化和云英岩化,铌钽矿与矽卡岩化、云英岩化关系密切,铌钽矿矿石类型主要有铌铁矿石、钽铁矿石。铌钽矿受碱长花岗岩控制,位于碱长花岗岩与矽卡岩化带附近,铌钽矿体明显增高,矿体向深部具有品位变富厚度变大的趋势,铌钽矿中的铌、钽元素来源于碱长花岗岩,碱长花岗岩为成矿提供物质、能量、流体等多种条件,使矽卡岩化带附近大量的Nb、Ta等稀有、稀土元素在二云母片岩中富集,形成了铌钽富矿体。文章针对矿区的实际情况,提出并分析了找矿标志及找矿潜力,以期取得找矿突破。     

西藏南木林县阿木雄北花岗闪长岩LA-ICP-MS锆石U-Pb年龄、岩石成因及构造意义

对冈底斯带中段阿木雄北花岗闪长岩进行LA-ICP-MS锆石U-Pb定年,主量和微量元素地球化学分析表明,花岗闪长岩的结晶年龄为61.8±1.2 Ma。花岗闪长岩为高钾钙碱性强过铝质花岗岩,Si O2含量为58.65%~73.5%,A/CNK值介于1.01~1.10之间,A/NK值介于1.34~2.19之间,稀土元素总量(∑REE)在99.96~201.42之间,在稀土元素配分模式图上,表现为倾斜下凹的浅"V"字型,轻、重稀土分馏明显;在微量元素蛛网图上,表现出相对富集Rb、Th、La、Pr、Hf、Nd、Dy,而亏损Ta、Nb、Ce、P、Zr、Ti的特征。花岗闪长岩显示出壳幔混源的特性,母源岩浆来自地幔,而后经AFC过程所形成的分异型I花岗岩,新特提斯洋板片回撤是其形成的深部地球动力学背景。     

中天山东段国宝山三叠纪高铷天河石花岗岩年代学及岩石地球化学研究

文章通过中天山东段国宝山天河石花岗岩岩石地球化学和锆石U-Pb定年研究,探讨其成岩年龄、岩体成因和成岩构造背景。该花岗岩具富硅(Si O_2=72. 70%~74. 20%)、富碱(Na_2O+K_2O=8. 99%~9. 20%)、钠质(Na_2O/K_2O=1. 35~1. 55)、弱过铝(A/CNK=1. 01~1. 08)和铁质(Fe O~T/MgO=4. 11~57. 77)特征,岩浆分异指数较高(DI=94. 01~95. 83);富集U、Sm、Zr、Hf、Ta等高场强元素(HFSE)和Rb、Nd、Pb元素,亏损Sr、P、Eu、Ti、Y等元素,稀土总量低(∑REE=55. 34×10~(-6)~140. 52×10~(-6)),轻稀土较重稀土略富集(LREE/HREE=0. 97~1. 47),具明显的铕负异常(δEu=0. 003~0. 04)。锆石U-Pb定年结果显示国宝山天河石花岗岩年龄为(247±3) Ma,天河石伟晶岩脉侵位于(202±3) Ma。天河石花岗岩岩石地球化学特征表明其为典型的A型花岗岩,结合区域地质背景分析,显示该岩体形成于板内张性构造环境;天湖岩群和星星峡岩群中的片岩和片麻岩为国宝山天河石花岗岩的主要贡献源岩,幔源岩浆内侵于中地壳使之发生部分熔融,且母岩浆经历了较强的结晶作用。