山东牟乳金矿带成矿演化机理探讨

山东牟乳金矿带位于华北地台东缘活化区。区内荆山群和胶东群变质绿岩建造是金矿化的矿源层。区内主要控矿构造为北北东、北东向构造。金矿床主要为含金硫化物石英脉型。成矿流体来源于地壳深部和后期大气降水的加入。对矿带成矿演化机理的研究表明，金矿形成经历了 3个阶段：①新太古至古、中元古代金初始矿源层形成阶段；②中元古代末期区域变质─混合岩化金再富集阶段和③燕山期构造─流体─金成矿作用阶段。     

物化探方法在浅覆盖区找矿工作中的应用效果

由于浅覆盖区特殊的地质景观,传统找矿方法难以直接获取地层、岩体、构造、矿产(化)等地质体信息,造成地质认识水平整体不高,最终影响找矿效果。本文以大兴安岭中北段东坡马场沟一带找矿工作为例,探讨利用物化探方法(地面高精度磁测、极化激发法、土壤测量)解译断裂构造、圈定岩体及矿化蚀变带、大致判别矿产种类,逐渐缩小找矿范围,最终查明矿(化)体的位置,发现金矿点1处、金矿化点2处、铅锌银矿点1处,取得了较好的找矿效果。     

贵州水银洞金矿床成因探讨及成矿模式

水银洞金矿床为贵州20世纪90年代中期通过成矿预测发现的层控型隐伏矿床,为中国第一个Ⅰ勘探类型的卡林型金矿床。通过10年来的勘查,成为滇黔桂“金三角”继烂泥沟之后的又一个特大型金矿床。本文简要介绍了矿床基本特征,从岩性、蚀变、孔隙度、同位素、包裹体等几个方面进行了研究,对矿床进行了成因探讨、建立了矿床成矿模式,总结了找矿标志,以期对下一步区域找矿提供借鉴。     

Stable isotope geochemistry of the Archean Val-d‘Or (Canada) orogenic gold vein field

A systematic study of the auriferous quartz veins of the Val-dOr vein field, Abitibi, Quebec, Canada, demonstrates that the C, O, S isotope composition of silicate, carbonate, borate, oxide, tungstate and sulphide minerals have a range in composition comparable to that previously determined for the whole Superior Province. The oxygen isotope composition of quartz from early quartz–carbonate auriferous veins ranges from 9.4 to 14.4 whereas later quartz-tourmaline-carbonate veins have ¹⁸O_quartz values ranging from 9.2 to 13.8 . Quartz-carbonate veins have carbonate (¹⁸O: 6.9–12.5 ; ¹³C: –6.2– –1.9 ) and pyrite (³⁴S: 1.2 and 1.9 ) isotope compositions comparable to those of quartz-tourmaline-carbonate veins (¹⁸O: 7.9–11.7 ; ¹³C: –8.0 – –2.4 ; ³⁴S: 0.6–6.0 ). ¹⁸O_quartz values in quartz-tourmaline-carbonate veins have a variance comparable to analytical uncertainty at the scale of one locality, irrespective of the type of structure, the texture of the quartz or its position along strike, across strike or down-dip a vein. In contrast, the oxygen isotope composition of quartz in quartz-tourmaline-carbonate veins displays a regional distribution with higher ¹⁸O values in the south-central part of the vein field near the Cadillac Tectonic Zone, and which ¹⁸O values decrease regularly towards the north. Another zone of high ¹⁸O values in the northeast corner of the region and along the trace of the Senneville Fault is separated by a valley of lower ¹⁸O values from the higher values near the Cadillac Tectonic Zone. Oxygen isotope isopleths cut across lithological contacts and tectonic structures. This regional pattern in quartz-tourmaline-carbonate veins is interpreted to be a product of reaction with country rocks and mixing between (1) a deep-seated hydrothermal fluid of metamorphic origin with minimum ¹⁸O=8.5 , ¹³C=0.6 and ³⁴S=–0.4 , and (2) a supracrustal fluid, most likely Archean seawater with a long history of water-rock exchange and with maximum ¹⁸O=3.9 , ¹³ C=–5.6 and ³⁴S=5.0 .     

The El Galeno and Michiquillay porphyry Cu–Au–Mo deposits: geological descriptions and comparison of Miocene porphyry systems in the Cajamarca district, northern Peru

El Galeno and Michiquillay are early to middle Miocene Cu–Au–Mo porphyry-related deposits located in the auriferous Cajamarca district of northern Peru. The El Galeno deposit (486 Mt at 0.57% Cu, 0.14 g/t Au and 150 ppm Mo) is associated with multiple dioritic intrusions hosted within Lower Cretaceous quartzites and shales. Emplacement of the porphyry stocks (17.5–16.5 Ma) in a hanging wall anticline was structurally controlled by oblique faults superimposed on early WNW-trending fold-thrust structures. Early K-feldspar–biotite–magnetite (potassic) alteration was associated with pyrite and chalcopyrite mineralisation. A quartz–magnetite assemblage that occurs at depth has completely replaced potassically altered rocks. Late- and post-mineralisation stocks are spatially and temporally related to weak quartz–muscovite (phyllic) alteration. High Au grades are associated with early intrusive phases located near the centre of the deposit. Highest Cu grades (~0.9% Cu) are mostly associated with a supergene enrichment blanket, whilst high Mo grades are restricted to contacts with the metasedimentary rocks. The Michiquillay Cu–Au–Mo deposit (631 Mt at 0.69% Cu, 0.15 g/t Au, 100–200 ppm Mo) is associated with a Miocene (20.0–19.8 Ma) dioritic complex that was emplaced within the hanging wall of a back thrust fault. The intrusive complex is hosted in quartzites and limestones. The NE-trending deposit is crosscut by NNW-trending prospect-scale faults that influenced both alteration and metal distribution. In the SW and NE of the deposit, potassic alteration zones contain moderate hypogene grades (0.14 g/t Au and 0.8% Cu) and are characterised by chalcopyrite and pyrite mineralisation. The core of the deposit is defined by a lower grade (0.08 g/t Au and 0.57% Cu) phyllic alteration that overprinted early potassic alteration. Michiquillay contains a supergene enrichment blanket of 45–80 m thickness with an average Cu grade of 1.15%, which is overlain by a deep leached cap (up to 150 m). Cu–Au–Mo (El Galeno-Michiquillay) and Au-rich (Minas Conga) deposits in the Cajamarca region are of similar age (early–middle Miocene) and intrusive rock type (dioritic) associations. Despite these geochronological and geochemical similarities, findings from this study suggest variation in metal grade between the hybrid-type and Au-rich deposits result from a combination of physio-chemical factors. These include variations in temperature and oxygen fugacity conditions during hypogene mineralisation resulting in varied sulphide assemblages, host rock type, precipitation of ubiquitous hydrothermal magnetite, and late hydrothermal fluid flow resulting in a well-developed phyllic alteration zone.     

伊什基里克金矿床地质特征

伊什基里克金矿床产于伊犁晚古生代弧间盆地、伊什基里克石炭纪裂陷中的酸性火山碎屑岩地层中,矿体呈脉状,受区域断裂构造控制。矿床的形成与早石炭世火山活动关系密切,提出了中低温火山热液矿床成因的认识。     

紧闭褶皱翼部的剪切变形作用——五台山绿岩带金矿化的一种构造控矿机制

五台山绿岩带中 ,与变质火山 沉积岩系直接相关的金矿化分布广泛 ,具有多种成矿和控矿机制。但就两种主要类型金矿———剪切带型金矿和铁建造型金矿的时空分布、地质特征和赋存的构造部位来看 ,它们都明显地与剪切变形 (韧性的或脆性的 )所产生的构造 热液活化作用有关 ,具显著的构造控矿意义。区域构造分析表明 ,五台山绿岩带的构造格架是一个多级和多期褶皱与断裂的组合 ,总的构造样式是一个紧闭程度向中心增强的复式倒转向形。它们是在北西 南东向挤压作用下递进变形的结果。在这一区域应力场作用下 ,处于不同构造部位的岩石发生变形分解作用 ,从而在紧闭褶皱的翼部产生一系列剪切变形带 ,构成了五台山绿岩带构造控矿机制。本文将以两类绿岩金矿的典型矿床为例 ,对这一控矿构造机制进行全面分析。     

胶东东部米山断裂变形带应力应变分析及其控矿特征研究

米山断裂是一多期变形的断裂。早期以韧性变形为主，后期以脆性变形为主，断裂变形具有准对称性，西盘变形强度大于东盘变形强度，变形强度决定了断裂带的蚀变及矿化特点。蚀变的分带结构与断裂的不同的矿化特征都与断裂的变形有关。因此，米山断裂的成生与发展，对胶东东部的成岩成矿具有重要作用，它控制了燕山早期花岗岩的侵入。韧性变形作用是金矿成矿的必要条件。     

熊耳山北坡拆离断层带地球化学特征及其与金银矿化的关系

熊耳山北坡发育一套典型的变质核杂岩构造，区内众多的金银矿床与变质核杂岩关系密切。研究表明，早期拆离断层带内Ａｕ，Ａｇ等成矿元素具有较高的富集系数，拆离断层对区内的缓倾层间破碎带型、陡倾构造蚀变岩型和爆破角砾岩型金银矿化具有不同形式的控制作用     

上海民防工程建设与地下空间开发利用

基于上海城市灾害特点与发展趋势的初步分析,提出充分利用地下空间资源、加强民防工程建设的建议,以有助于进一步提高上海防灾抗灾减灾综合能力。结合上海特殊的地质条件,分析了地下空间民防工程建设中的主要问题及其防治对策,以期提高城市土地综合利用效率,并有效保障城市安全与可持续发展。