西昆仑地区塔木MVT型铅锌矿床成矿作用和成矿物质来源探讨

MVT型铅锌矿是西昆仑地区重要的铅锌矿床类型之一.为了探明西昆仑地区该类型矿床的成矿作用过程和成矿物质来源,本文以塔木矿床为例,在野外调研基础上,进行了光片鉴定、铅硫同位素、稀士元素和成矿元素研究,得到矿石中方铅矿的δ34SCDT为-5.04‰～+3.67‰,反映出油田卤水与深层卤水的混合特征;由铅同位素分析结果计算出表面年龄为461～481 Ma(早于泥盆纪438～410 Ma);由稀土元素分析数据得出岩(矿)石/球粒陨石标准化分配模式图表明,成矿物质主要来自地层.因而判定主要成矿物质可能来源于前泥盆系地层.喜马拉雅期逆冲推覆构造作用所引发的大规模热卤水运移、循环过程,导致矿质的进一步富集、沉淀.     

Pseudotachylytes in the southern border fault of the Cenozoic intracontinental Teletsk basin (Altai, Russia)

The Cenozoic intracontinental Teletsk basin in the Central Asian Altai Mountains is composed of a complexly structured northern and a more simple southern sub-basin. These sub-basins formed in two distinct kinematic stages when first the NNW-striking Teletsk- and then the NE-striking West-Sayan shear zones became reactivated in the Cenozoic under dominant NS-oriented horizontal compression. Although the entire Teletsk basin strikes roughly NS, the southern sub-basin is parallel to the NNW-trending, amphibolite facies Teletsk ductile shear zone, while the northern sub-basin is NS-striking and flanked by differently structured, greenschist facies basement. Basement reactivation closely controlled the southern sub-basin formation, but this is less clear for the northern sub-basin. Contrasts between northern and southern basement and the exclusive occurrence of pseudotachylytes along the margins of the southern basin are explored for their contribution to the formation of the Teletsk basin with two distinct sub-basins.In the ductile shear fabric of the basement flanking the southern sub-basin, concordantly interleaved pseudotachylytes and isolated breccia lenses reflect local brittle deformation along the ductile fabric. The genetic link between breccia lenses and pseudotachylyte occurrences was defined by microstructural investigation. It allows to explore their possible development in a dextral strike–slip zone. These rocks occur in a large fault-bounded segment of the basement. The geometry of the structures in the segment is comparable with a dextral strike–slip sidewall-ripout structure along the Teletsk shear zone. Seismic slip related to pseudotachylytes is attributed to the sudden stress release on the NNW-striking Teletsk shear zone, when the latter became unconstrained by reactivation of the NE-trending West-Sayan fault zone at its northern boundary. The boundary of the sidewall-ripout structure was reactivated as a large listric fault in a later stage. The northern sub-basins roughly develop along an NS strike and are assumed to reflect reactivation of the ductile shear zone underneath the variably structured greenschist facies basement outcropping along the flanks of the sub-basin.     

云南腾冲地块北部空树河组一个菱铁矿结核中的C、O同位素变化特征

空树河组是滇西腾冲地块北部的石碳－二叠纪冈瓦纳相沉积。菱铁矿结核见于该组顶部的黑色泥岩中。将一个结核通过中心切开，在切面上由中心向边缘用牙钻等间隔提取10个样品。同位素测试结果显示，δ^13C自中心向边缘逐渐由－8．09％减为－16．12％，最外一个样例外（－15．39‰），而δ^18O自中心向边缘逐渐由－10．64‰增加为0‰左右。δ^13C的变化情况表明，菱铁矿结核可能形成于硫酸盐还原带。在解释δ^18o的变化情况时，推测在结核开始生长时可能有δ^18O亏损的大气降水掺入，随着埋藏深度的逐渐加大，孔隙水的O同位素逐渐趋近正常海水的值（0‰）。     

Sm-Nd ISOTOPIC AGE OF LAMPROPHYRES IN THE GEZHEN GOLD-BEARING SHEAR ZONE ON HAINAN ISLAND AND ITS GEOLOGICAL IMPLICATIONS

Sm-Nd isotopic compositions of eight lamprophyre samples, which come from the Gezhen gold-bearing shear zone on western Hainan Island, are measured. The Sm-Nd isochron age is 495.98±13.14 Ma, (143Nd/144Nd) 0=0.512094, εNd(t) ranges from +1.80 to +2.00 and TDM from 982 Ma to 1196 Ma (average: 1060 Ma). The authors point out that the whole-rock Sm-Nd isochron age (495.98 ± 13.14 Ma) really represents the petrogenetic age of lamprophyre and the time of magmatism during subsequent subduction.     

华北陆块北缘西段中元古代与裂谷作用有关的铁、稀土、多金属矿床特征及成因

华北陆块北缘西段狼山—白云鄂博裂谷系中元古代形成的大型多金属矿床 ,是我国重要的铁、稀土、铜、铅、锌矿产地。矿床为产于沉积岩中热水沉积型多金属矿床。其形成受地层、构造控制 ,与裂谷作用有着密切的关系。裂谷系内外分支的地质环境及矿床矿种不同 ,导致矿床特征及成因具有一定差异。白云鄂博铁、稀土矿床为钾、钠、磷等含量较高的热水沉积型 ,霍各乞铜、铅、锌多金属矿床为与中基性火山岩有关的过渡热水沉积型 ,东升庙和甲生盘等铅、锌多金属矿床为热水沉积型。文中将对上述矿床分别进行论述。     

Geochronology of Gold Deposits and Its Implication for Metallogenesis in the Fengxian-Lixian Area, Qinling Orogenic Belt, China

Abstract: A series of super large‐scale and large‐scale Pb and Zn, and Au deposits are distributed in the Qinling orogenic belt, China. Gold deposits were generally ascribed to Carlin‐type originated from circular meteoric water. Visible and coarse‐grained gold (up to over 3mm in grain size) was recently identified in some gold deposits in the Fengxian‐Lixian area, Qinling. Au‐bearing quartz lodes related to magmatism were discovered in the Xiaogouli gold deposit. Two types of Au‐bearing quartz veins, i.e., NW‐trending quartz veins and NE‐trending quartz veins cutting strata are widely present in the Baguamiao gold deposit. Both are spatially associated with each other. The former is generally snake–like, S‐shape or zigzag, which was resulted from plastic deformation by ductile shearing, being generally cut by the latter. The latter is generally linear with widely developed bleaching alteration zones in its adjacent wall rocks, which symbolizes the superimposition of brittle deformation and filling and metasomatism of magmatic hydrothermal solution in ductile shear zones after uplifting of the shear zones near the surface. The NW‐trending quartz veins contain Au of lower than 3ppm. The NE‐trending quartz veins contain Au of more than 3 ppm, so that NE‐trending quartz veins and the adjoining altered rocks are important ores. The NW‐trending Au–bearing quartz vein was dated as 210.61.26 to 232.581.59 Ma by ⁴⁰Ar–³⁹Ar method, i.e., late Indosinian epoch (Triassic). The NE‐trending Au–bearing quartz vein was dated as 131.910.89 to 197.451.13 Ma by ⁴⁰Ar–³⁹Ar method, i.e., Yanshanian epoch (Jurassic). The ⁴⁰Ar–³⁹Ar age of the NW‐trending Au–bearing quartz veins represents the age of the ductile shear formation. The isotope data of the NE‐trending quartz veins indicate that gold mineralization was closely related to Indosinian and Yanshanian granite intrusives not only in time and space, but also in origin.     

内蒙古色尔腾山山前断裂(乌句蒙口-东风村段)的断层活动与古地震事件

通过对色尔腾山山前断裂乌句蒙口 -东风村段的遥感资料解释、野外地质地貌考察 ,并通过对重点地段的古地震探槽开挖 ,获得了该断裂段晚更新世晚期以来的垂直位移速率是 0 88～ 1 83mm a ,全新世中期以来的垂直位移速率是 0 89mm a。通过 2个大型探槽的开挖、古地震事件分析和相关堆积物的断代研究 ,以及用逐次限定方法分析整个断层段上的古地震事件 ,认定该断裂段上全新世以来发生了 5次古地震事件 :事件 1发生在距今 90 0 0± 130 0年 ,事件2发生在距今 6 5 0 0± 5 0 0年 ,事件 3发生在距今 5 5 70年左右 ,事件 4发生在距今 4 2 0 0± 30 0年 ,事件 5发生在距今 32 5 0± 2 5 0年。晚更新世晚期到距今 1万年之间 ,古地震事件很不完整。全新世以来的 5次古地震事件表现出一定的丛集特征。最早的一丛事件发生在距今 890 0年左右 ,第2丛发生在距今 6 5 0 0～ 5 70 0年之间 ,第 3丛事件发生在距今 32 5 0～ 4 2 0 0年之间。第 1丛与第 2丛古地震事件之间间隔为 2 4 0 0年左右 ,而第 2丛与第 3丛古地震事件之间仅间隔 15 70年左右。距今 32 5 0年以来 ,该断裂段上还没有发生过错断地表的地震事件 ,已经超出了古地震丛之间的重复间隔。因此 ,它是色尔腾山前活动断裂带上具备潜在危险的一个活动断裂段。     

A comparison of tectonic ambient shear stress value in China with that in western USA

Introduction The stress status of the earths crust is closely related to global structure, the direction of plate movement, the drive mechanism of plate, earthquake cause, etc. Therefore the researches of the stress status of the earths crust and the process of dynamic evolution are paid a great attention to by many people around the world (Zoback, Zoback, 1980; Zoback, et al, 1989; Zoback, 1989; Spence, 1997; Fuchs, 1997; Plenefish, Bonjer, 1997; Muller, et al, 1997; XU, et al, 1989; WAN…     

天山西部中山带积雪变化趋势与气温和降水的关系——以巩乃斯河谷为例

根据位于巩乃斯河谷的天山积雪雪崩研究站近30年来的年最大雪深、月平均气温、月降水量观测记录，用平均差值法、最小二乘法、自回归滑动平均法检验了天山西部中山带积雪、冷季降水、冷季平均气温的变化趋势，结果表明，天山西部中山带积雪呈增加趋势，近30年来年平均增加1.43%，与青藏高原、南极大陆及格陵兰冰盖表面积雪积累增加相一致。天山西部中山带冷季气温和降水的变化趋势也是增加的，其中冷季降水平年平均增加0．12％，而冷季气温升高了0．8℃，积雪与冷季气温之间存在着弱的负相关关系，而与冷季降水呈显著的正相关关系。积雪的增加主要是因为气候变暖引起的冷季降水的增加对积雪增加的贡献大于由于冷季气温升高而造成积雪减少的贡献的结果。     

西方城市空间结构研究的理论进展

文章综述了西方国家城市空间结构研究的理论进展，概括了城市空间结构各时期研究的主要内容和理论观点，展望了城市空间结构未来研究的趋势和方向。工业化以前西方城市空间结构研究主要侧重于城市表面形态的揭示，把城市空间结构同发展过程分离开来论述其特性。工业化以后的城市空间结构研究进展十分迅速，在研究中十分重视引入新思想、新理论、新技术和新方法。在不同时期出现了不同的学术派别，并总结出诸多城市空间结构的理论模型。