新疆东准噶尔野马泉花岗岩体的年龄和地球化学特征

新疆东准噶尔野马泉花岗岩体是一个主要由花岗闪长岩、二长花岗岩和碱长花岗岩组成的复式花岗岩体。三种岩石的锆石U-Pb年龄在误差范围内有很好的一致性(～300Ma),指示野马泉岩体是在晚石炭世侵位的,也属于东准噶尔地区后碰撞阶段的岩浆作用产物。元素地球化学组成表明,花岗闪长岩、二长花岗岩和碱长花岗岩均属于准铝质,其主量元素和微量元素如CaO、Al2O3、Na2O、K2O、Rb、Sr与SiO2之间有明显的线性关系,三种岩石在不相容元素蛛网图和稀土元素配分模式上均表现出相似的特征,Eu负异常程度也随着SiO2含量的增加而提高。此外,野马泉岩体不同岩石有非常近似的Hf同位素组成,其εHf(t)值为+11.8～+12.7。因此,年龄结果和地球化学特征说明,野马泉复式花岗岩体很可能是由同源岩浆通过一定的岩浆演化形成的。     

Low temperature alteration of magmatic Ni-Cu-PGE sulfides as a source for hydrothermal Ni and PGE ores: A quantitative approach using automated mineralogy

Magmatic Ni-Cu-PGE sulfide assemblages are almost ubiquitously comprised of pyrrhotite-pentlandite-chalcopyrite(-pyrite). Sulfide alteration is common during syn- or post-magmatic fluid interaction, usually replacing sulfides with amphiboles or serpentine. However, some are altered to a low temperature (<200 °C) hydrothermal assemblage of pyrite-millerite-chalcopyrite (PMC). An example is the Ni-Cu-PGE mineralisation in the Grasvally-Norite-Pyroxenite-Anorthosite (GNPA) Member, northern Bushveld Complex, which displays a continuum of mineralogical styles formed through progressive alteration: Style 1 primary pyrrhotite-pentlandite-chalcopyrite; which is altered to Style 2 pyrrhotite-pyrite-pentlandite-chalcopyrite; Style 3 pyrite-pentlandite-chalcopyrite; Style 4 pyrite-pentlandite-millerite-chalcopyrite; and Style 5 pyrite-millerite-chalcopyrite-cubanite. Modelling using CHILLER confirms this mineralogical sequence is thermodynamically possible at ∼200 °C. Quantitative characterisation using automated Energy-Dispersive X-ray spectroscopy mapping alongside in situ laser ablation analyses determined mineral proportions, major and trace element concentrations and deportments in each style. The early loss of pyrrhotite removes over half of the bulk Fe and S during the initial stages of PMC alteration, increasing Cu, Ni and PGE tenors of the remaining sulfides significantly. As water–rock interaction progresses, pyrrhotite is replaced by pyrite and pentlandite by millerite, with concurrent losses in Fe, S and Ni. Copper is lost throughout the alteration, and is most pronounced in the more advanced stages. The fluids responsible were most likely acidic and oxidised, with metals mobilised as chloride complexes. Using Rh as an immobile normalising element, the overall mass loss in the most altered samples is calculated to be up to 90%, consistent with textural relationships that indicate 40–90% volume loss from Styles 2–5, with sulfides replaced by secondary silicates, including phlogopite, quartz, chlorite, pyroxenes and minor amphiboles. Magnetite is not a significant alteration product and thus Fe is mobilised, or incorporated into silicates. Most trace elements present in the magmatic sulfide (the IPGE, Rh and Bi) remain in the sulfide phases, and are effectively transferred to pyrite during PMC alteration, except Pd, which remains in pentlandite, and is liberated from the sulfide assemblage when pentlandite disappears. Selenium tenors increase slightly with alteration, demonstrating that alteration decreases S/Se ratios. The significant mobilisation of Ni, Cu and Pd during PMC alteration produces fluids enriched in these elements that may represent a metal source for a number of enigmatic hydrothermal Ni deposits such as Avebury, Enterprise and Talvivaara, whose metal sources remain speculative. The PMC alteration of the GNPA Member may be specifically a source for the nearby Waterberg hydrothermal Pt deposit. Furthermore, this study has implications not only for magmatic ore deposits, but also for the general implications of sulfide transformation and metal transfer in ore systems in general.     

云南德钦良通铅锌矿控矿地质条件

良通铅锌矿产于印支期石英闪长岩（δο15）内部裂隙、破碎带内,控矿因素为岩浆岩、岩浆岩侵位的地层、构造等,中低温热液型铅锌多金属矿床,矿区及外围具有较大的找矿前景。     

云南各类岩浆岩水系沉积物元素富集规律

经对云南各类岩浆岩水系沉积物39种元素含量统计后认为:超基性岩、基性岩、中-中酸性岩、酸性岩、碱性岩、峨眉山玄武岩水系沉积物富集元素差别较大。水系沉积物测量对源岩地球化学特征具有很好的继承性。     

黑龙江翠宏山铅锌多金属矿床岩浆岩特征及成矿年龄

翠宏山铅锌多金属矿床产在花岗岩体与下寒武统西林群铅山组变质岩系的接触带内,是一矽卡岩型铅锌多金属矿床.岩浆活动强烈,具有脉动活动特点,形成的岩石类型主要有二长花岗岩、正长花岗岩、碱长花岗岩.总结该区花岗岩岩石地球化学特征后,认为该花岗岩具有由"Ⅰ"型向"A"型过渡特点,并采用锆石U-Pb方法确定了地表和深部二长花岗岩的...     

初论内蒙古长山壕金矿床的成矿时限

长山壕金矿床是近年来在白云鄂博裂谷带上发现的一处具有代表性的超大型金矿床,是中国最大的金矿之一。对长山壕金矿区内含矿石英脉中的黑云母和白云母进行了40Ar/39Ar同位素年代测定,结果表明矿石中黑云母的形成年龄为256.3±1.8Ma,白云母的形成年龄为250.9±1.5Ma~246.0±1.6Ma。结合前人对该区域岩体的测年结果推测出大规模岩浆活动不仅为成矿提供重要的热源,而且提供了重要的物质来源。岩浆演化后期的热液中成矿物质的出溶沉淀是主要的成矿过程,随着温度降低,压力减小,含矿热液中的黑云母和白云母相继结晶,含矿热液中的金及其他成矿元素也在此期间沉淀聚集。     

理解岩浆系统的物理过程

岩浆系统是一种复杂性动力系统,暗示岩浆系统的演化具有多重分支现象,即其演化路径包含一系列平衡过程与突变事件.因此,岩浆系统的物理过程是理解岩浆形成与演化及其相关地质过程的关键.邓晋福教授及其学术团队长期坚持岩浆系统物理过程的研究,在火成岩成因、火成岩构造组合、岩浆活动与成矿作用的关系和相关的地球深部过程等研究领域都做出了杰出的贡献.本文集刊登了部分相关的研究成果,以强调岩浆系统物理过程的重要性.我们撰写此文,目的是简要介绍本文集的主要内容和强调岩浆系统物理过程的研究意义.     

班韦卢地块和伊鲁米德带区域地质及构造演化特征

"变质克拉通"作用为稳定克拉通的被动边缘受到陆内碰撞作用的影响而发生变质作用和岩浆作用。班韦卢地块位于赞比亚东北部,被认为是坦桑尼亚克拉通或刚果克拉通的变质克拉通边缘,伊鲁米德带位于班韦卢地块的东南部,为其元古宙变质克拉通边缘。本文通过对两者的基底、地层和岩浆岩特征的系统整理研究,发现元古宙变质基底从北向南随变质作用的增强,由片岩类渐变为片麻岩类,这可能是由于两者构造层位的不同和遭受变质克拉通作用的期次不同共同造成或其中之一造成的。穆瓦超群大规模沉积作用年龄为1800Ma左右,姆波洛科索群沉积碎屑主要来源于盆地南部的变质基底,锆石年龄显示含少量太古宙地壳组分。多期次的岩浆岩具有相似的地球化学性质,其来源可能为太古宙地壳的局部熔融作用。根据地层和岩浆岩特征,可以将构造演化分为3个阶段:班韦卢地块和伊鲁米德带"变质克拉通"阶段(≥1880Ma)、稳定沉积阶段(1880Ma~1050Ma)和伊鲁米德带"变质克拉通"阶段(≤1050Ma),不同阶段地幔岩浆加入量较少,但可作为热源导致太古宙地壳多次熔融而形成元古宙地质体。     

Internally consistent data for sulphur‐bearing phases and application to the construction of pseudosections for mafic greenschist facies rocks in Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–CO2–O–S–H2O

The Holland and Powell internally consistent data set version 5.5 has been augmented to include pyrite, troilite, trov (Fe_0.875S), anhydrite, H₂S, elemental S and S₂ gas. Phase changes in troilite and pyrrhotite are modelled with a combination of multiple end‐members and a Landau tricritical model. Pyrrhotite is modelled as a solid solution between hypothetical end‐member troilite (trot) and Fe_0.875S (trov); observed activity–composition relationships fit well to a symmetric formalism model with a value for w_trot?trov of ?3.19 kJ mol^?1. The hypothetical end‐member approach is required to compensate for iron distribution irregularities in compositions close to troilite. Mixing in fluids is described with the van Laar asymmetric formalism model with a_ij values for H₂O–H₂S, H₂S–CH₄ and H₂S–CO₂ of 6.5, 4.15 and 0.045 kJ mol^?1 respectively. The derived data set is statistically acceptable and replicates the input data and data from experiments that were not included in the initial regression. The new data set is applied to the construction of pseudosections for the bulk composition of mafic greenschist facies rocks from the Golden Mile, Kalgoorlie, Western Australia. The sequence of mineral assemblages is replicated successfully, with observed assemblages predicted to be stable at X(CO₂) increasing with increasing degree of hydrothermal alteration. Results are compatible with those of previous work. Assemblages are insensitive to the S bulk content at S contents of less than 1 wt%, which means that volatilization of S‐bearing fluids and sulphidation are unlikely to have had major effects on the stable mineral assemblage in less metasomatized rocks. The sequence of sulphide and oxide phases is predicted successfully and there is potential to use these phases qualitatively for geobarometry. Increases in X(CO₂) stabilized, in turn, pyrite–magnetite, pyrite–hematite and anhydrite–pyrite. Magnetite–pyrrhotite is predicted at temperatures greater than 410 °C. The prediction of a variety of sulphide and oxide phases in a rock of fixed bulk composition as a function of changes in fluid composition and temperature is of particular interest because it has been proposed that such a variation in phase assemblage is produced by the infiltration of multiple fluids with contrasting redox state. The work presented here shows that this need not be the case.