Comparison of the Typical Metallogenic Systems in the North Slope of the Tongbai-East Qinling Mountains and its Geologic Implications

The Tongbai-East Qinling Mountains,an important part of the Central orogenic belt,is one of the most important metallogenic belts in China and contains lots of orogenic-type and VMS-type (Volcanogenic Massive Sulfide type)metallogenic systems.The Dahe and Shuidongling VMS-type Cu-Zn deposits,located in the Erlangping Group in Tongbai and East Qinling Mountains,respectively, show similar geological and geochemical features.The Huoshenmiao Formation in the East Qinling region and the Liushanyan Formation i...     

Mantle Branch Structure in the South-Central Segment of the Da Hinggan Mts.,Inner Mongolia and Its Ore-controlling Role

Abstract: Mantle branch structure is the third tectonic unit of multiple evolution of a mantle branch. It is not only the main mechanism of intercontinental orogeny, but also an important ore-forming and ore-control structure. Studies on geotectonic evolution, regional geological characteristics and ore-forming and ore-control structures have shown that since the Mesozoic the Da Hinggan Mts. region has entered a typical intercontinental orogenic stage, and it is closely related to mantle branch activities. The south-central segment of the Da Hinggan Mts. is a typical mantle branch structure and possesses obvious magmatic-metamorphic complexes in the core, detachment slip beds in the periphery and overlapped fault depression basins. Moreover, all of these are the principal factors leading to ore formation and ore control in the region. This paper also further explores the mechanism of mineralization in the south-central segment of the Da Hinggan, summaries the rules of mineralization, puts forward the models of mineralization and points out future ore-exploring orientation.     

Geology, Geochemistry and Minerogenesis of the Shijuligou Zinc–Copper Deposit in Gansu, China

Abstract: The Shijuligou deposit was separated by an arcuate ductile shear zone cross the center of the deposit region, resulting in the difference between the southern and northern ore bodies. The lead (Pb) isotopic data of ores of the Shijuligou copper deposit have averages of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb in 17.634, 15.444, and 37.312, respectively. It has been shown that ore-forming metals originated from intrusive and extrusive rocks in the upper part of ophiolites. The sulfur isotopic data of pyrite and chalcopyrite in the northern part change from +7.61‰ to +8.09‰ and +4.95‰ to +8.88‰ in the southern part. Isotopes of δ18O in the Shijuligou copper deposit are between +11.1‰ and +18.6‰, with the calculated δ18OH2O at +0.65‰. It is suggested that the mineralized fluid is a mixture of magma fluid, meteorological water, and seawater through circulating and leaching metals from the volcanic rocks. The zircon uranium-lead (U–Pb) dating of gabbro is 457.9±1.2 Ma, and the lower crossing age of the discordant and concordia curves of pyroxene spilite of zircon is 454±15 Ma. It is indicated that the Shijuligou deposit formed in a new ocean crust (ophiolite) of the back-arc basin in the late Ordovician. Mineralization should occur in the intermittence period after strong volcanic activity, and the age should be the late Ordovician. Moreover, the mineralization of ophiolite-hosted massive sulfide deposits in the ancient orogenic belt of the late Ordovician in the northern Qilian Mountains was controlled by the primary fault/fracture, with the forming of a metallogenic hydrothermal system by a mixture of volcanic magma fluid and seawater, which circularly leached the metallogenic metals from the volcanic rocks, resulting in their accumulation. The ore bodies were transformed with morphology and metallogenic elements. Jasperoid is an important sign for prospecting such deposits. There were many island arcs in the continent of China. This study provides evidence for understanding and exploration of ophiolite-hosted massive sulfide deposits in western China, especially in the area of northern Qilian Mountains.     

西昆仑--喀喇昆仑及其邻区岩石圈结构、演化中几个问题的探讨

西昆仑-喀喇昆仑位于西藏高原西北,西构造结(Western Syntaxis)的东侧,是当前国际地学界关注的热点地区之一.本文不准备对该地区岩石圈结构、演化及其多重效应作全面论述,仅以近年青藏高原项目实施中涉及的几个较重要问题作探讨;经过对已获得的地震深探测和地质、地球化学资料的分析研究,提出青藏高原西北缘不存在塔里木向西昆仑山作长距离的"A型俯冲",晚新生代以来岩石圈"面对面水平挤压-拆沉作用"是形成西昆仑陆-陆碰撞造山带的主要原因.对众所关注的库地蛇绿岩形成时代,提出了新的SHRIMP-Ⅱ,U-Pb锆石测年年龄,上限为510±4Ma;对原特提斯大洋、康西瓦大型走滑断裂带的形成、演化作了探讨.     

祁连山冷龙岭宁缠河3号冰川表面流速特征分析

2009年9月对祁连山冷龙岭宁缠河3号冰川外围建立控制网, 于冰川表面布设了13根标志杆, 随后分别于2010年7月、2010年9月再次对设立在冰川表面的花杆点进行测量, 获取2009/2010年度、2009年9月-2010年7月与2010年7-9月3个时段宁缠河3号冰川表面流速.结果显示: 2009/2010年度宁缠河3号冰川最大流速出现在海拔4 430 m附近, 为3.76 m·a^-1;2009年9月-2010年7月表面流速最大值出现在海拔4 430 m附近, 为0.32 m·月^-1;2010年7-9月最大流速出现在海拔4 380 m附近, 为0.47 m·月^-1.总体来看, 2009/2010年度宁缠河3号冰川纵剖面上流速变化较为缓和, 显示出流速随海拔变化而变化的规律. 但不同季节表面流速在纵剖面上的分布情况不同, 横剖面上主流线附近流速最大, 向冰川两边逐渐递减, 各观测点均平行于主流线方向向冰川末端运动, 表现出冰川运动一般规律. 在冰川表面运动速度观测区域内东南边缘流速略大于西北边缘, 同时与规模相近的冰川运动速度相比, 宁缠河3号冰川运动速度较大.     

太行山南缘晚更新世以来河流阶地的发育及其新构造运动意义

太行山南缘的武家湾河流经太行山与华北平原两大地貌单元的过渡地带,较太行山内部其他水系对新构造运动的响应更为敏感,能较好地记录区域地壳抬升历史。以武家湾河下游平甸河为研究重点,通过野外河流阶地级序及沉积特征的调查并结合光释光（OSL）测年结果,厘定了平甸河4级河流阶地,T4、T3、T2及T1阶地河拔高度分别为61～96 m、35～54 m、19～43 m、3～5 m,分别形成于974 kaBP、739 kaBP、483 kaBP、23 kaBP,根据对阶地成因的探讨,认为T4、T3、T2阶地为构造阶地,T1阶地为气候阶地,阶地资料揭示晚更新世（Qp3）太行山南缘经历3次间歇性构造抬升后至少隆升了90 m: 第一次抬升26～42 m、抬升速率111～179 mm/a,第二次抬升11～27 m、抬升速率043～105 mm/a,第三次抬升16～39 m、抬升速率035～085 mm/a。本研究为河流阶地对新构造运动的响应研究提供了实际材料,对晚更新世太行山的形成及演化研究具有较重要的参考价值。     

Characteristics of beaver ponds on deltas in a mountain environment

Many beaver ponds in the Rocky Mountains, that have been described in the literature, are in‐channel ponds that are relatively small and short‐lived. This paper describes floodplain beaver ponds on low‐gradient deltas in glacial finger lakes in Glacier National Park, Montana. These ponds are distinctly larger, probably fed by hyporheic flow, and stable and long‐lived. Ponds examined were, with one exception, 44 years old. Glacial discharge is present in each valley where beaver ponds occupy low‐gradient deltas, and this discharge likely sustains pond water level over the course of the summer. As glaciers recede and disappear, deltaic beaver ponds dependent on hyporheic flow may be negatively affected. Copyright © 2012 John Wiley & Sons, Ltd.     

祁连山西段测震指标异常综合应用

通过对1980年以来至今14个指标的全时间扫描,并使用祁连山西段地区Ms5．0地震进行对应。结果表明,选取A值、AC值、A（b）值、b值、Mf值和地震活动度S值进行同步异常分析,能显著提高祁连山西段地区的有震报震率,但有漏报。对目前地区异常集中区进行时间扫描,结果显示,祁连山西段地区出现同步异常,认为2012年或稍长时期有发生Ms≥5．0中强震的可能。     

近50 a来新疆区域与天山典型流域极端洪水变化特征及其对气候变化的响应

以年极端洪水超标率来反映区域极端洪水, 分析了新疆区域极端洪水变化; 以年最大洪峰记录分析了天山山区主要河流极端洪水变化规律, 并用14站资料分析了天山山区气候变化特征, 讨论了天山主要河流极端洪水变化对区域气候变化的响应. 结果表明: 受气候变暖影响, 1957-2006年全疆极端洪水呈区域性加重趋势, 尤其南疆区域极端洪水明显加剧, 北疆区域也有加重趋势, 但相对较缓. 全疆及北疆、 南疆在20世纪90年代中期以来都处于洪水高发阶段. 近50 a来, 在新疆区域洪水呈加重趋势的变化背景下, 发源于天山南坡的托什干河和库玛拉克河年最大洪峰流量呈显著增加趋势, 发源于天山北坡的玛纳斯河与乌鲁木齐河年最大洪峰流量虽有增加, 但是变化趋势较缓. 以年最大洪峰流量发生转折年为界, 天山典型流域托什干河、 库玛拉克河、 玛纳斯河和乌鲁木齐河在20世纪90年代(或80年代)以来与前期相比, 呈现出相似的变化特征: 年最大洪峰流量明显增大, 年际间变化更加剧烈, 洪水年更频繁. 以年最大洪峰流量发生转折年份为界, 玛纳斯河、 托什干河和乌鲁木齐河后期的年最大洪峰集中日期较前期推迟2~9 d, 库玛拉克河却提前5 d. 玛纳斯河、 乌鲁木齐河和库玛拉克河后期的集中度较前期增加0.8%~8.3%, 托什干河减小1.1%. 1961-2010年, 新疆天山山区气温明显上升, 升温率为0.34 ℃·(10a)^-1, 1997年以后明显增暖; 天山山区降水显著增加, 增加速率15.6 mm·(10a)^-1, 同时极端降水强度增大、 频数增多. 近50 a来天山主要河流极端洪水变化与区域增温以及天山山区极端降水事件增多等有密切关系.     

大兴安岭中段柴河地区碎斑熔岩的发现及其意义

近年,在大兴安岭柴河地区开展1：5万区调时发现了碎斑熔岩体.区内发育晚侏罗世满克头鄂博组（J₃m）、玛尼吐组（J₃mn）及白音高老组（J₃b）火山岩,广泛分布在二十四道沟、敖尼尔-四道沟及柴河-固里河3个火山喷发盆地中.所发现的固里河、敖尼尔两个碎斑熔岩体,即是白音高老期火山活动晚期侵出的重要组成部分.固里河碎斑熔岩体呈一北东向延伸的椭圆形穹状岩体,可划分出内部相（似斑状）、过渡相（霏细质）和边缘相（玻质）3个相带,主要由流纹质碎斑熔岩构成;敖尼尔碎斑熔岩主体呈近东西向,平面上呈似蘑菇状,可划分出2~3个相带,其岩石类型基本同固里河碎斑熔岩体.它们的发现,对研究大兴安岭地区火山岩的形成、演化及指导找矿等具有重要意义.