Stable isotope characteristics and origin of ore-forming fluids in copper-gold-polymetallic deposits within strike-slip pull-apart basin of Weishan-Yongping continental collision orogenic belt, Yunnan Province, China

More than 140 middle-small sized deposits or minerals are present in the Weishan-Yongping ore concentration area which is located in the southern part of a typical Lanping strike-slip and pull-apart basin. It has plenty of mineral resources derived from the collision between the Indian and Asian plates. The ore-forming fluid system in the Weishan-Yongping ore concentration area can be divided into two subsystems, namely, the Zijinshan subsystem and Gonglang arc subsystem. The ore-forming fluids of Cu, Co deposits in the Gonglang arc fluid subsystem have δD values between −83.8‰ and −69‰, δ¹⁸O values between 4.17‰ and 10.45‰, and δ¹³C values between −13.6‰ and 3.7‰, suggesting that the ore-forming fluids of Cu, Co deposits were derived mainly from magmatic water and partly from formation water. The ore-forming fluids of Au, Pb, Zn, Fe deposits in the Zijinshan subsystem have δD values between −117.4‰ and −76‰, δ¹⁸O values between 5.32‰ and 9.56‰, and Δ¹³C values between −10.07‰ and −1.5‰. The ore-forming fluids of Sb deposits have δD values between −95‰ and −78‰, δ¹⁸O values between 4.5‰ and 32.3‰, and Δ¹³C values between −26.4‰ and −1.9‰. Hence, the ore-forming fluids of the Zijinshan subsystem must have been derived mainly from formation water and partly from magmatic water. Affected by the collision between the Indian and Asian plates, ore-forming fluids in Weishan-Yongping basin migrated considerably from southwest to northeast. At first, the Gonglang arc subsystem with high temperature and high salinity was formed. With the development of the ore-forming fluids, the Zijinshan subsystem with lower temperature and lower salinity was subsequently formed. Translated from Mineral Deposits, 2006, 25(1): 60–70 [译自: 矿床地质]     

Biomarkers in the Molar Tooth （MT）-Bearing Limestones in the Jilin-Liaoning Area of China

The origin of Molar Tooth (MT) carbonates has been argued for more than 100 years, which are a kind of Proterozoic carbonates especially composed of microsparite with ptygmatically folded and sheet-like structures. Biomarkers detected in the microcalcsparite from the Wanlong and Xingmincun formations in the Jilin-Liaoning area showed there are abundant normal alkanes, isoprenoids, hopanes, steranes, alkylmethylcyclohexanes, and alkyleyclohexanes, indicating a diversity of biological source: long-chain isoprenoids, the major components of chlorophyll, such as C19, C20, a kind of major biomarkers synthesized early by isoprenoid monomers; hopanes a type of characteristic biomarkers from prokaryote, such as archaebacteria and cyanobacteria; sterane a biomarker for eukaryote; and two kinds of alkanes with C17, C18 as the main peaks representing aquatic bacteria and with C23, C24 as the main peaks representing fungi, respectively. Biomarker analysis showed that MT is the result of bacterial and algal activities, which is a kind of organisms between aerobic and anaerobic bacteria, reproducing well in normal or slightly saline sea water under weak oxidation-reduction conditions, resulting in rapid deposition of calcite as microsparite clue to some mechanisms.     

西藏色布塔铜钼矿床中辉钼矿Re-Os定年及其成矿意义

色布塔铜钼矿床位于冈底斯成矿带北部,具有细脉浸染状矿化,围岩蚀变发育等斑岩型铜钼矿床特征.本文使用电感耦合等离子体质谱仪TJA X-series ICP-MS对色布塔铜钼矿床的花岗斑岩中的辉钼矿进行ReOs同位素定年研究,获得了6件样品的模式年龄为87.52±1.35～88.8±1.26Ma,等时线年龄为88.8±1.5Ma.本文研究成果表明,色布塔铜钼矿成矿时代为晚白垩世早期,属燕山期构造-岩浆活动的产物.     

Evolution of the Late Triassic Paleo-uplift in the Southwestern Upper Yangtze Region and its Tectonic SignificanceEI北大核心CSCD

Based on field geological survey and stratigraphic analysis, a Late Triassic Paleo-uplift is identified in the southwestern upper Yangtze region. The tectonic features, evolution history and tectonic significance of this paleo-uplift are discussed in detail in this paper. The results suggest that the hiatus of the Upper Triassic in the southwestern upper Yangtze region was resulted from the paleo-uplift that roughly parallel to the southwest margin of the upper Yangtze region. The formation of the paleo-uplift is related to the closure of the Jinshajiang-Ailaoshan-Songma-Babu and Ganzi-Litang Oceans and their subsequent collisional orogenesis along the southwest margin of the upper Yangtze region. The forebulges of the Youjiang and Chuxiong Foreland Basins were formed by the closure of the Jinshajiang-Ailaoshan-Songma-Babu Ocean, comprising the paleo-uplift at the end of the Early Triassic. Then the forebulge of the Xichang Foreland Basin was developed by the closure of the Ganzi-Litang Ocean in the Norian, and became a new part of the paleo-uplift. Owing to the termination of the Youjiang Foreland Basin at the end of the Rhaetian, the paleo-uplift was composed only of the forebulges of the Chuxiong and Xichang Foreland Basins. The discovery of the paleo-uplift will help us to better understand the prototype of the Sichuan Basin and the tectonic evolution of the southwestern upper Yangtze region during the Late Triassic. © 2017, Science Press. All right reserved.     

基于边坡渐进破坏特征对传统极限平衡法几点假设的合理分析

边坡的渐进破坏特征一直以来是边坡计算仿真中的一个难点。实际边坡的破坏很少是一个整体达到极限状态,突然滑动的过程,往往是逐步发展由局部破坏到最终整体失稳,即临界状态小扰动导致的链式多米洛骨牌式失稳。利用颗粒流软件,设计了0.1 m粒径高10 m土坡的数值模型,粒间黏聚力为36 kPa,摩擦系数为0.36。初始模型在重力作用下不会发生破坏,通过单独折减粒间黏聚力到18 kPa使得边坡破坏,监测竖向颗粒组group的变化获取每20 000个时间步的边坡破坏形态,实现200 000个时间步内边坡的渐进破坏过程。边坡总是从局部开始破坏,坡体物质的运移造成次一级破坏,形成最终的近似弧形的滑动面,说明滑体不是整体下滑,不是刚体,不是整体达到极限状态;坡体内应力的变化也不是单调的,有涨有落,均区别于当前极限平衡法中有限条块的刚体假设;滑动面上同时达到极限状态假设,问题本身是静不定的,通过给出条间力的传递方式使之静定可解;整体分析不能考虑破坏的局部化和渐进特征。这说明边坡计算方法的未来在于能反映动力问题和材料破坏特征的离散元方法。     

Investigating the swelling pressure of highly compacted bentonite/sand mixtures under constant-volume conditions

Acta Geotechnica - Compacted bentonite/sand mixtures are often considered as sealing/backfilling materials in deep geological disposal for radioactive waste. This study investigates the swelling...     

甘肃西和县金崖沟金锑矿特征浅析

甘肃西和县金崖沟金、锑矿位于南秦岭北部的岷县鹿儿坝—西和崖湾—两当广金坝金、汞、锑成矿亚带上。矿带长约1 km,由一条NE向高角度断层F1控制,矿(化)体主要处于断层的下盘即南东盘,矿体产状280°~315°∠67°~80°,不连续,呈透镜状、扁豆状,在纵向上及垂向上矿体产状均变化较大,形态主要随断层错动形成的虚脱空间形态的变化而变化。金矿呈透镜状、板状、长条状,品位1.05~3×10~(-6),厚度0.78~3.20 m不等,锑品位1.14%~3.41%,平均厚度1.26 m。金矿对岩石有一定的选择性,主要以铅锌铜硫化矿物包裹金形式赋存于断层破碎带中的硅化角砾岩中。锑矿不具规模,多分布于两断层交汇处呈鸡窝状产出,即在构造复杂流体流通较好且有利的容矿空间成矿,呈浸染状、放射状、针状,锑矿与金矿局部伴生,局部独立存在。     

沉积物磷原位钝化技术研究进展

水体磷含量是湖泊富营养化最主要的限制因子之一.伴随着湖泊流域工农业发展,外源污染物的长期输入致使沉积物中蓄积了大量的磷及其他污染物.湖泊沉积物一方面是水体磷重要的汇,但另一方面还是水体磷重要的源.在单纯控制湖泊外源污染条件下,沉积物磷的释放仍可导致水体持续富营养化,湖水水质得到明显改善通常需要数十年,因此控制湖泊沉积物内源污染释放是快速恢复湖泊水质必不可少的措施.沉积物内源污染控制技术包括生物修复、环保疏浚以及原位钝化技术.受水深等环境条件限制,生物修复技术和环保疏浚在深水、亚深水型湖泊难以实施.沉积物磷原位钝化技术具有生态、经济、快速和效果稳定等特点,在控制湖泊底泥内源污染中可望发挥重要作用,尤其适合于深水、亚深水型湖泊内源污染控制.系统阐述了不同沉积物原位钝化剂的钝化原理,对比分析了铝盐、铁盐、钙盐和粘度矿物作为磷钝化剂的优缺点和应用条件,概述了国内外沉积物原位钝化技术的应用现状,在此基础上提出了沉积物原位钝化技术未来的重点研究方向:一是研究发展新型钝化剂;二是因地制宜,探索适合不同类型湖泊的底泥原位钝化技术体系;三是加强底泥原位钝化技术与其他技术的联合应用研究与示范;四是加强钝化剂负面影响评价,建立科学的应用技术方案.     

柴达木盆地西部新生界陆相湖盆碳酸盐岩沉积环境与沉积模式*

利用野外露头、岩心、测井录井和分析化验资料,对柴达木盆地西部(简称“柴西地区”)新生界干柴沟组湖相碳酸盐岩进行了研究,划分了其沉积微相类型,研究了其分布规律,分析其形成环境和控制因素,并建立了相应沉积模式。该区湖相碳酸盐岩在垂向上与碎屑岩频繁互层,湖相碳酸盐岩包括颗粒灰岩、藻灰岩、泥晶灰岩和混积岩4大类11种,划分出了灰泥坪、颗粒滩、藻丘(礁)、浅湖湾以及(半)深湖泥灰岩相等5种沉积微相。通过分析不同碳酸盐岩及其微相时空展布特征,认为其发育主要受控于湖盆构造运动、湖平面变化、陆源碎屑注入、古气候与古水介质条件、古地貌与古水深环境,并在此基础上建立了柴西湖相碳酸盐岩的沉积模式。研究认为柴达木盆地西部干柴沟组沉积时期,湖盆为典型咸化湖盆,构造活动相对稳定,湖平面上升达到峰值。碳酸盐岩主要发育在湖侵期,高频湖平面变化形成了碳酸盐岩与碎屑岩频繁互层。在枯水期,盆地坡折处发育碎屑岩滩坝或三角洲前缘沉积;在湖侵期,盆地坡折处发育了鲕粒滩及藻灰岩,盆地洼陷区发育泥灰岩或灰质泥岩。     

南秦岭东部新元古代埃达克质岩的发现及其地质意义

秦岭造山带是一条复合型大陆碰撞造山带,存在若干新元古代构造岩浆事件的遗迹,它们对深化认识南北秦岭汇聚-碰撞过程和Rodinia超大陆聚合具有重要意义。本文对南秦岭东部豆腐尖岩体英云闪长岩开展LA-ICP-MS锆石U-Pb年代学和全岩主微量元素地球化学研究。代表性样品的²⁰⁶Pb/²³⁸U加权平均年龄为860.7±6.0Ma,表明其形成时代为新元古代。岩石地球化学特征表现为高SiO₂(62.41%～68.89%)、高Al₂O₃(15.33%～17.33%),富Na₂O(4.23%～5.80%)和高Na₂O/K₂O比值(1.11～2.41),富Sr(>400×10^-6),低MgO(0.55%～2.08%),低Y(7.40×10^-6～18.20×10^-6)、Yb(0.63×10^-6～1.62×10^-6),...