大兴安岭南段早二叠世两类火山岩岩石地球化学特征及其构造意义

大兴安岭南段二叠系大石寨组发育两套火山岩，即林西地区拉斑玄武岩系列的细碧－角斑岩类和大石寨地区钙碱性岩石系列玄武岩和玄武安山岩类。细碧岩的主元素以富铁为特征，成分类似于N－MORB，微量元素表现为岛弧拉斑玄武岩的地球化学特征。细碧岩类形成于大石寨裂陷槽强烈拉张的中心位置，是地幔源区较高程度部分熔融的产生。大石寨地区玄武岩和玄武安山岩类的化学成分表现为大陆缘弧火山岩的地球化学特点，形成于大石寨裂隙槽拉张中心以外的环境，是地幔物质较低程度部分熔融和地壳物质严重混染的产物。大石寨裂隙槽中火山岩的这种独特的成分和组合特点可能反映了裂隙槽的形成是一个快速而短暂的强烈拉张过程。     

铧厂沟金矿床地质特征及控矿冈素分析

铧厂沟金矿床位于勉－略－宁三角地带成矿有利部位。矿区出露中下泥盆统三河口群和中上元古界碧口群。矿床内发育的韧性剪切带经历了右行（韧性）－左行（韧脆性）－右行（脆性）多期（次）活动矿化受透镜状细碧岩控制,分布于韧性剪切带之中。矿体蚀变强烈,新生矿物定向排列,脉体中矿物具亚颗粒、变形纹、变形条带等料内变形特征。同位素地球化学及稀土分析结果表明,基性火山岩是金的矿源层。金矿的形成富集与韧性剪切带多期（次     

东准噶尔海相火山岩型小瑞江铜矿地质特征及其找矿方向

在西伯利亚板块库兰卡孜干晚古生代岛弧上，古亚洲洋壳对西伯利亚古陆南缘俯冲一碰撞不同阶段形成了多种类型的金、铜、汞矿床（点），新发现的产在下泥盆统细碧岩中的海相火山岩型小瑞江铜矿，地表铜化矿带具有一定规模，铜矿受一定的层位和岩性控制，其特征与海相火山岩黄铁矿型白银铜矿特征相似，属海底基性火山喷流沉积形成的矿床，有着广阔的找矿前景．     

Geochronology and geochemistry of the Cambrian (~518 Ma) Chagantaolegai ophiolite in northern West Junggar (NW China): constraints on spatiotemporal characteristics of the Chingiz–Tarbagatai megazone

The Chingiz–Tarbagatai megazone is a well-known early Palaeozoic unit in eastern Kazakhstan that extends into northern West Junggar along the Tarbagatai–Xiemisitai–Sharbuti Mountains. Here, we report new geochronological and geochemical data for the Chagantaolegai ophiolite, discovered in the south Xiemisitai Mountains, north of the Heshituoluogai Valley in West Junggar. The laser ablation inductively coupled plasma mass spectrometry zircon U–Pb ages of a gabbro in the Chagantaolegai ophiolite are 517 ± 3 and 519 ± 3 Ma, corresponding to the early to middle Cambrian. Serpentinized peridotites in the ophiolite show low rare earth element (REE) abundances (0.61–0.94 μg/g) and slight loss of middle REEs. Chagantaolegai metagabbro samples have flat to very slightly depleted patterns in light REEs, with a narrow range of REE abundances. The Chagantaolegai spilites and metagabbros display similar flat patterns, which show a geochemical signature similar to mid-ocean ridge basalt (MORB) between Yb and Zr, and diverge from MORB towards the most incompatible elements in MORB-normalized multi-element diagrams. The Th/Yb vs. Nb/Yb diagram for the spilite samples also suggests a mid-ocean ridge (MOR) setting. To summarize, all the geochemical characteristics of the Chagantaolegai ophiolite point to MOR ophiolite. The positive ε_Nd(t) values (0.78 to +9.85) suggest that the gabbros and spilites were derived from a depleted mantle source with chemical inhomogeneity. The Chagantaolegai ophiolite spatiotemporal characteristics correlate well with the Kujibai and Hongguleleng ophiolites in the northern part of West Junggar, and the Zhaur and Balkybek ophiolites in eastern Kazakhstan. These data show that early Palaeozoic oceanic crust started to develop in the early to middle Cambrian in northern West Junggar. Stratigraphic correlations also suggest that the South Saur Fault and an inferred fault buried in the Heshituoluogai depression are the northern and southern boundary of the Chingiz–Tarbagatai megazone, respectively.     

A Petrographic and Mineralogical Study of Volcanic Rocks from the Mayaxueshan Area, North Qilian Fold Belt, NW China

The Ordovician volcanic rocks in the Mayaxueshan area have been pervasively altered or metamorphosed and contain abundant secondary minerals such as albite, chlorite, epidote, prehnite, pumpellyite, actinolite, titanite, quartz, and/or calcite. They were denoted as spilites or spilitic rocks in terms of their petrographic features and mineral assemblages. The metamorphic grades of the volcanic rocks are equivalent to that of the intercalated metaclastic rocks. This indicates that both the spilitic volcanic rocks and metaclastic rocks in the Mayaxueshan area have formed as a result of Caledonian regional metamorphism. We suggest that the previously denoted spilitic rocks or altered volcanic rocks should be re-denoted as metabasalts or metabasaltic rocks. The metamorphic grade of the volcanic rocks increases with their age: prehnite-pumpellyite facies for the upper part of the Middle Ordovician volcanic rocks, prehnite-pumpeilyite to lower greenschist facies for the lower part of the Middle Ordovician vol     

安康牛山火山岩区基础地质及金银铜的成矿条件

安康牛山地区的海相火山岩构成安康隆起的主体。经两年的研究取得了如下认识和成果:①火山岩岩石学、岩石地球化学研究表明,郧西群火山岩可分为上、下两个岩性段,岩石类型计有石英角斑岩、钾石英角斑岩及其同质火山碎屑岩;耀岭河群为细碧岩、钠长辉绿岩及其同质火山碎屑岩,火山岩组合为石英角斑岩-细碧岩,缺失中性角斑岩类,前者为钙碱性系列,后者为拉斑玄武岩系列,含钙碱性系列分子。火山岩具双模式特点,为裂谷环境产物。加里东晚期或华力西早期侵位的酸性侵入岩为岛弧环境产物。②首次研究并划分出七条韧性剪切带,在空间上呈近南北,和南东-北西两组方向,推测其为共轭韧性剪切带组合。③论述了恒河以东,付家河以西地段的线性构造和环形构造,并在此基础上论证了猴子崖-牛山主峰一带为一大型构造穹窿。④本区火山变质岩的变质矿物有七种组合类型和两个变质相。⑤本区首次发现了高压变质相系的蓝片岩(钠钙闪石绿片岩)。这对阐明安安隆起、平利隆起,乃至整个秦岭造山带的构造演化具有重要的大地构造意义。⑥基于Ma区和Pan区铜银矿点和矿化地段的发现和金银铜矿化特征、成矿条件的分析,初步认为本区已知的火山热液脉型和火山变质热液脉型铜矿不具备形成工业矿床的地质条件,金矿产成矿因素较为复杂,其成矿前景尚欠明确,银矿产尚有一定的成矿潜在前景。笔者等确立的找矿指导思想是以银为主的金银铜综合找矿。     

安康牛山火山岩区基础地质及金银铜的成矿条件

安康牛山地区的海相火山岩构成安康隆起的主体。经两年的研究取得了如下认识和成果:①火山岩岩石学、岩石地球化学研究表明,郧西群火山岩可分为上、下两个岩性段,岩石类型计有石英角斑岩、钾石英角班岩及其同质火山碎屑岩;耀岭河群为细碧岩、钠长辉绿岩及其同质火山碎屑岩,火山岩组合为石英角斑岩-细碧岩,缺失中性角斑岩类,前者为钙碱性系列,后者为拉斑玄武岩系列,含钙碱性系列分子。火山岩具双模式特点,为裂谷环境产物。加里东晚期或华力西早期侵位的酸性侵入岩为岛弧环境产物。②首次研宄并划分出七条韧性剪切带,在空问上呈近南北,和南东-北西两组方向,推测其为共轭韧性剪切带组合。③论述了恒河以东,付家河以西地段的线性构造和环形构造,并在此基础上论证了猴子崖-牛山主峰一带为一大型构造穹窿。④本区火山变质岩的变质矿物有七种组合类型和两个变质相。⑤本区首次发现了高压变质相系的蓝片岩(钠钙闪石绿片岩)。这对阐明安康隆起、平利降起,乃至整个秦岭造山带的构造演化具有重要的大地构造意义。⑥基于Ma区和Pan区铜银矿点和矿化地段的发现和金银铜矿化特征、成矿条件的分析,初步认为本区已知的火山热液脉型和火山变质热液脉型铜矿不具备形成工业矿床的地质条件,金矿产成矿因素较为复杂,其成矿前景尚欠明确,银矿产尚有一定的成矿潜在前景。笔者等确立的找矿指导思想是以银为主的金银铜综合找矿。     

广西龙胜丹洲群细碧岩锆石U－Pb及Sm－Nd等时线年龄

用单颗粒锆石Ｕ－Ｐｂ及全岩、全岩－矿物Ｓｍ－Ｎｄ等时线法对广西龙胜丹洲群细碧岩进行了地质年代学研究。结晶锆石年龄为９７７±１０Ｍａ，代表细碧岩的形成时代；锆石Ｕ－Ｐｂ及全岩Ｓｍ－Ｎｄ等时线均反映出～０．６Ｇａ的一次后期事件年龄，很可能代表一次较大规模富ＣＯ２流体的热液蚀变作用时代，即本区受细碧岩层控的滑石矿的成矿年龄；细碧岩全岩矿物Ｓｍ－Ｎｄ内部等时线年龄为２０１±４０Ｍａ，代表了印支期岩浆热事件的时代。     

金平龙脖河铜矿区变钠质火山岩系地球化学研究:Ⅰ.主微量元素特征和形成环境探讨

云南龙脖河铜矿区浅变质火山岩、辉绿岩与火山碎屑岩均具明显富钠贫钾特征;从各种岩石化学分类图解可得到互相不同的判别结果。轻稀上从略富集到略亏损的分配模式及低的RB、Sr含量表明具从洋中脊至岛弧拉斑玄武岩过渡的特征。各种火山岩TiO2与Nb、Th、Y、重稀土元素之间存在好的正相关关系,稀土模式具平移的特征均表明存在强的钠交代细碧岩化作用。钠交代作用与铁矿化同时发生。上述地球化学特征和大红山群变钠质火山岩系相一致。     

Geochemical character and tectonic significance of Early Devonian keratophyres in the New England Fold Belt,eastern Australia

Extrusive and high level intrusive Early Devonian keratophyres are the oldest in situ igneous rocks in the Tamworth Block of the New England Fold Belt of eastern Australia. They show extensive evidence of degradation, including the destruction of magmatic phases, the growth of low grade metamorphic minerals, and changes in composition involving the dilution of elemental abundances in response to silica addition. Relations between the less mobile minor and trace elements, and limited data on clinopyroxene compositions, lead to the conclusion that these Early Devonian volcanic rocks are mostly calc‐alkaline volcanic arc andesites with minor dacite. These rocks unconformably overlie a sequence of Early Palaeozoic forearc basin deposits, indicating that the Early Devonian marks a period of readjustment of tectonic elements within the New England Fold Belt, associated with a marked east‐directed stepping out of the magmatic arc. Generation of the keratophyres in a subduction zone environment limits the position of the trench to 100 km east of the Peel Fault System.