西藏拉萨地块盐湖复式岩基中花岗斑岩的成因及其对班-怒洋闭合时限的制约

花岗质岩浆作用是大陆地壳演化、爆发式火山活动、稀有金属成矿等的关键过程。位于拉萨地块北部班公湖-怒江缝合带西段的盐湖复式岩基,是班公湖-怒江特提斯洋俯冲消减岩浆响应的重要组成部分。以西藏革吉县盐湖复式岩基中的花岗斑岩为研究对象,对其进行岩相学、锆石U-Pb年龄及岩石地球化学研究,探讨其成因。研究结果表明,盐湖复式岩基花岗斑岩的锆石U-Pb年龄为103.8±0.8 Ma(MSWD=3.0,n=25),侵位于早白垩世晚期。盐湖复式岩基花岗斑岩铝饱和指数(A/CNK)为1.05～1.08,显示弱过铝质特征,具有高K₂O、Na₂O含量,低Mg^#值(12.43～22.36)的特征,为高钾钙碱性I型花岗岩。盐湖复式岩基花岗斑岩富集K,亏损Ba、Nb、P、Zr、Ti,具有强的负Eu异常(δEu=0.20～0.48),稀土元素配分曲线呈轻稀土元素较陡、重稀土元素较平坦的右倾型,ΣREE=81.33×10^-6～121.61×10^-6,LREE/HREE=5.75～6.74,具有较高的Y(20.1...     

胶东盘子涧金矿床成矿流体特征：来自包裹体、H-O同位素证据

盘子涧金矿床地处华北板块胶辽隆起区,栖霞-蓬莱金成矿带上。金矿的形成主要与区内控矿断裂-盘子涧断裂和中生代岩浆岩有关。为研究该矿床成矿流体性质及演化,并控讨矿床成因,对该矿床开展不同阶段的包裹体进行岩相学、显微测温、包裹体激光拉曼及 H-O 同位素分析研究。盘子涧金矿床成矿热液期可划分为 4 个成矿阶段,从早到晚分别是黄铁矿-石英阶段（Ⅰ阶段）、石英-黄铁矿（绢云母）阶段（ Ⅱ 阶段）、金-石英-多金属硫化物阶段（ Ⅲ 阶段）和石英-碳酸盐阶段（ Ⅳ 阶段）。其中 Ⅱ、III 阶段为主成矿阶段。不同成矿阶段的流体包裹体有 3 种类型,分别是富液气液两相盐水包裹体、含 CO2 三相包裹体和纯液相包裹体。显微测温结果显示,成矿流体的完全均一温度介于 142～348 °C,主要集中于 200～300 ℃,盐度介于 4.44%～10.98% NaCl eqv。石英的 δDV‐SMOW值为-74.6‰～-68.5‰,δ18OV‐SMOW 值为 +11.65‰～+13.92‰。显示成矿流体为中低温、低盐度的 CO2‐H2O‐NaCl 体系,来源于地幔,以岩浆热液为主,并伴有部分大气降水加入。矿床成因类型属石英脉型金矿。     

山东栖霞杨础地区包裹体及稳定同位素地球化学特征及其意义

栖霞杨础地区属于胶辽隆起区,该地区广泛发育太古宙变质深成岩,元古宙变质表壳岩,中生代沉积岩、火山岩、酸性侵入岩以及新生代沉积物,主构造线呈NE向,是主要的控矿构造,其内赋存有众多中小型金矿床。本文通过对该区域内新发现的金及多金属矿化点的矿(化)体的特征及部分矿石的流体包裹体、同位素等特征分析,初步查明了该地区金及多金属矿床成因并建立了成矿模式。     

辽宁东部地区桥头组微生物诱发沉积构造(MISS）的发现及意义

Through the re-investigation and understanding of the “mud crack-like sedimentary structure” in the Qiaotou Formation from late Mesoproterozoic to early Neoproterozoic in the eastern Liaoning, and by comparing with the contemporaneous microbial induced sedimentary structure (MISS) in other areas of the NCC, For the first time, the fractured sedimentary structure discovered in the Qiaotou Formation in Liaoning was identified as MISS.Results: The fissure structure found in the Qiaotou Formation is MISS, which is formed by the physical destruction of microbial mats.Conclusions: The MISS identified in the Qiaotou Formation has spindle-like, three-connected ornithoid and partially connected branched morphology, so it is speculated that the Qiaotou Formation was formed in the sedimentary environment of the upper part of the supratidal zone. This discovery provides basis for stratigraphic and sedimentological studies of the Qiaotou Formation, and is of great significance for studying the evolution of early life on earth and exploring the long-term impact of biota on the atmosphere and hydrosphere.     

辽宁东部地区桥头组微生物诱发沉积构造(MISS）的发现及意义

Through the re-investigation and understanding of the “mud crack-like sedimentary structure” in the Qiaotou Formation from late Mesoproterozoic to early Neoproterozoic in the eastern Liaoning, and by comparing with the contemporaneous microbial induced sedimentary structure (MISS) in other areas of the NCC, For the first time, the fractured sedimentary structure discovered in the Qiaotou Formation in Liaoning was identified as MISS.Results: The fissure structure found in the Qiaotou Formation is MISS, which is formed by the physical destruction of microbial mats.Conclusions: The MISS identified in the Qiaotou Formation has spindle-like, three-connected ornithoid and partially connected branched morphology, so it is speculated that the Qiaotou Formation was formed in the sedimentary environment of the upper part of the supratidal zone. This discovery provides basis for stratigraphic and sedimentological studies of the Qiaotou Formation, and is of great significance for studying the evolution of early life on earth and exploring the long-term impact of biota on the atmosphere and hydrosphere.     

藏北革吉北部竟柱山组地球化学与碎屑锆石U- Pb年代学特征及构造意义

沿班公湖- 怒江缝合带近东西向不连续分布的上白垩统竟柱山组（K 2j）,是洋- 陆转换后的陆相沉积。因其东西向空间跨度较大,其准确的形成时限和砂岩源区的构造环境存在争议。本文采集西藏革吉县北部竟柱山组粗砂岩,对其碎屑锆石进行LA- ICP- MS U- Pb测年和主微量元素分析。样品碎屑锆石U- Pb谐和年龄值范围集中于100~130Ma和150~170Ma;在碎屑锆石年龄频谱图上,主要出现111. 7Ma和160. 1Ma两个峰值。最新的碎屑锆石年龄加权平均值为105. 3Ma,表明竟柱山组应在早白垩世末期之后沉积。SiO 2含量为52. 92%~69. 47%,Al 2O 3含量为5. 22%~14. 34%。高场强元素Ta、Nb、Ti亏损,Hf、Th及REE富集;大离子亲石元素Ba亏损,Rb、K富集。主微量元素特征及判别图解表明,研究区竟柱山组砂岩源区构造背景为大陆岛弧环境,物源为中酸性火成岩。