Geochemical evolution of the early Paleozoic collisional magmatism from autochthonous migmatites and granitoids to multiphase granite intrusions (Sharanur and Aya complexes,Baikal Region)

Overall petrologic and geochemical data indicate that the early Paleozoic magmatism in the Olkhon area of the Baikal Region exhibits diverse types of granitoids, whose time of formation is estimated at a narrow age interval of 500-465 Ma. This magmatism was responsible for the formation of both autochthonous gneiss-migmatite-granitoid suites (Sharanur complex) and multiphase intrusions (Aya complex) emplaced into the upper horizons of the continental crust. In major-element chemistry, K₂O/Na₂O values, and rare-element composition the migmatite-plagiogranites and calc-alkaline and subalkaline granitoids of the Sharanur complex are similar to the host gneisses and schists, as they were likely derived from melting of the ancient metamorphic substratum of the Olkhon series. In new isotope-geochemical characteristics (ICP MS method) the Sharanur granitoids are close to the first-phase biotite granites of the Aya massif, whose further geochemical evolution was governed mainly by intrachamber magmatic differentiation leading to the production of second-phase leucogranites enriched in HREE and HFSE (in particular, Ta and Nb) and depleted in Sr, Ba, Eu, Li, and LREE. The origin of the autochthonous and intrusive granitoids is related to early Paleozoic collision events within the Olkhon metamorphic terrane, while the formation of syncollisional granitoids is best explained by both melting of the crust protolith (Sharanur complex) and magmatic differentiation (multiphase Aya intrusion). All mineralogical and geochemical characteristics indicate that these granitoids are distinguished from rare-metal pegmatoid granites and Li-F and Rb-Be-Nb pegmatites, whose vein bodies crosscut the granitoids, and are regarded as middle Paleozoic rocks, which mark the transition to within-plate magmatism in the Baikal Region.     

西江沿岸(肇庆段)岩溶塌陷地质灾害特征

岩溶塌陷是西江沿岸(肇庆段)平原地区的主要地质灾害之一。论述研究区内岩溶塌陷的规模及危害,在分析岩溶塌陷时空分布规律、成因的基础上,针对岩溶塌陷特征提出合理规划工程建设及抽水排水、尽量避开易发岩溶塌陷地区等防治措施,为地区地下工程开发建设和防灾减灾提供地质依据。     

甘南拉尔玛矿山环境地质问题的成因分析及防治方案

甘肃是矿产资源大省,矿产开发规模大、强度高。但是,由于有关管理部门的松懈,导致矿山环境地质问题较突出。本次基于对拉尔玛矿山环境地质的实地调查,论述、分析了危害矿山环境地质的因素有地质体结构和人工活动。其中人工活动是主要因素,多是由于在生产过程中不遵守矿山采矿规范和环境生态保护意识淡薄所致,给矿山附近的牧民和牲畜均造成了不同程度的危害,从而导致矿山停业整改。作者结合当地和矿山的实际情况,提出了一些可行、合理、有效的防治方案和措施,以期达到有效恢复矿山环境地质的目的。     

金沙江“长江第一湾”段河谷地貌、沉积与发育

"长江第一湾"位于青藏高原东南边缘及其向云贵高原过渡的边缘地带,金沙江在该区深深切割了青藏高原东南边缘。按照河谷地貌与沉积特征,其宗—大具段金沙江可划分为其宗—下落鱼段、虎跳峡段和大具盆地段。详细描述了各河段的地貌与第四纪沉积特征,并根据同位素年龄等数据讨论了河流沉积物、湖相沉积物及冰川与冰水沉积物,特别是河谷中厚达150~250m的埋藏沉积物的成因与形成时代。在此基础上,讨论了研究区及邻区自中新世以来的金沙江河谷发育与青藏高原隆升问题。     

印尼苏门答腊岛地体划分及其区域成矿背景

根据不同地层系统、沉积古地理、古生物地理区系、岩浆旋回等特征,可将苏门答腊岛划分为2类异地地体:东苏门答腊地体(亲冈瓦纳地体)和西苏门答腊地体(亲华夏地体)。2个不同地体的古地理演化和板块构造运动规律控制了区域金属矿床分布。海西期—印支期金属矿床的形成和分布受控于大陆边缘的火山弧,而燕山期则和裂谷岩浆侵入活动和海底扩张(或地幔隆起)有关。新生代金—银金属矿床沿苏门答腊—巴厘散大断裂两侧成带分布,受控于陆缘火山弧的岩浆活动。     

两类厄尔尼诺事件发展年秋季印度洋海温异常特征对比

基于1951—2010年逐月海气多要素观测资料,对比分析了两类厄尔尼诺事件发展年秋季印度洋的海温异常及大气响应特征,探讨了印度洋偶极子的发生与两类厄尔尼诺事件特征的可能联系。结果表明,两类厄尔尼诺事件的发展年均会出现印度洋偶极子,但出现的概率不同:大多数东部型厄尔尼诺事件都会伴有正位相印度洋偶极子发生;而仅一半的中部型厄尔尼诺事件期间会出现正位相印度洋偶极子的异常海温型,且强度较弱。从印度洋偶极子与两类厄尔尼诺事件的物理联系上看,东部型厄尔尼诺事件期间,印度洋偶极子的发生与其强度联系密切:印度洋偶极子发生在东部型厄尔尼诺事件较强期间,两者通过海洋大陆的异常强下沉运动及大范围负异常降水相联系;东部型厄尔尼诺事件偏弱时并无印度洋偶极子出现,海洋大陆异常下沉运动及负异常降水很弱。然而,中部型厄尔尼诺事件期间印度洋偶极子的发生与其强度并无显著的关系,而与太平洋高海温区的位置存在一定的可能联系:在有印度洋偶极子发生的中部型厄尔尼诺事件发展年秋季,热带太平洋异常高海温区的位置相对偏东,海洋大陆出现显著下沉运动和大范围负异常降水,热带东印度洋为大范围强异常东风控制;但无印度洋偶极子发生的中部型厄尔尼诺事件时,热带太平洋高海温区位置相对偏西,极弱的海洋大陆下沉支对热带印度洋异常海温作用非常有限。     

山东省东平县大牛地区铁矿成因类型及找矿方向研究

大牛地区铁矿位于汶上东平铁矿成矿带中北部。区内第四系广布,以临沂组为主,含矿地层为隐伏新太古代泰山岩群山草峪组磁铁角闪石英岩。基底构造线方向为NW 310°,褶皱构造、断裂构造均较发育,其规模不等,矿体受一定程度破坏。矿石自然类型为细粒条带状、条纹状磁铁角闪石英岩型,一般与顶底板岩石（黑云变粒岩）界线分明,沿走向与倾向常见夹石（层）且具分支复合现象,总体属有限延伸的板状矿体,主要控矿因素为地层、区域构造和区域变质作用,成矿类型为沉积变质型铁矿。     

Sedimentary types and features of gravity flow depositional systems from Late Oligocene to Early Miocene in Liwan sag,Pearl River Mouth Basin

The sedimentary characteristics of gravity flow depositional systems(GFDS)in Liwan sag,Pearl River Mouth Basin,has not been clear. Based on a large number of high-revolution seismic data and a small amount of borehole data,the sedimentary types,spatial-temporal evolution,and controlling factors of the gravity flow depositional systems in Zhuhai Formation and the basal Zhujiang Formation in the Liwan sag are summarized. Four sedimentary types of the GFDS,can be identified according to the different seismic facies associations. Pordelta turbidite fan,the first type,is relatively small-scale compared with other type,but formed at the same time with the shelf edge delta,which is likely to be sand rich. Mass transport complex deposition,the second type,is featured by fault scarps,multiple small detachment faults,internal deformation structures such as sliding and compression,and overall southeast movement. The channelized slope fan,the third type,with lots of small channels on the head,contains microfacies such as turbidite channel,channel-levee complex and crevasse splay. The basin floor fan,the fourth type,is a bidirectionally down-lapped,mound-shaped and strong amplitude continuous intermediate-frequency reflection seismic facie association,and its microfacies such as incised valley,channel filling,front crevasse fan and sheet like lobe can be recognized. It is believed that the coupling of tectonics,climate,sea level change and sediment supply results in the GFDS in the study area and different types of GFDS are formed at different period during the base level cycle change. This research can provide a reference for the summary of gravity flow depositional law and hydrocarbon exploration in the ultra-deep water area.     

蒸发背景沉积序列精细刻画及沉积学解译:以鄂尔多斯盆地中部中奥陶统马五6亚段为例*

云膏共生组合是受化学沉积分异作用控制而形成的岩石组合,对其沉积序列精细刻画,有利于揭示诸多蒸发环境下的沉积学信息。依据鄂尔多斯盆地中部奥陶系马家沟组五段6(简称“马五₆亚段”)亚段钻井、岩心资料,开展了岩石宏观和微观观察、典型沉积序列刻画等工作。研究结果表明: (1)鄂尔多斯盆地中部马五₆亚段普遍发育碳酸盐岩与蒸发岩共生组合,主要由10种岩石类型构成;(2)主要发育5种沉积序列,下云上膏的岩性组合和序列顶部多发育暴露面等特征表明单个序列具有向上变浅、变咸的演化特征,是蒸发台地叠合海水渐次补给作用的结果;(3)在局限—蒸发台地环境下,主要发育潟湖/滩间海、颗粒滩、灰泥丘、台坪4种沉积亚相及11种沉积微相,与经典的蒸发潮坪序列在岩性组合与沉积构造方面存在明显的差异;(4)马五₆亚段沉积期发育2次海平面升降,沉积环境可分别对应于云(膏)质潟湖—灰泥丘/颗粒滩—膏质潟湖—蒸干膏质潟湖和灰泥丘/颗粒滩—膏质潟湖—蒸干膏质潟湖—台坪。该研究结果可为鄂尔多斯盆地马五₆亚段沉积环境与海平面变化研究提供系统的岩石学证据。     

甘肃省红层与丹霞地貌研究的回顾与展望

甘肃省新近系—侏罗系碎屑岩红色或杂色地层（俗称红层）分布广泛,在漫长的地质演化过程中形成了众多造型多样的丹霞地貌,呈现出较高的科研、美学及地学旅游价值。受社会经济条件的制约,关于甘肃省红层和丹霞地貌多数景观尚“处在深闺人未识”的境界。文章在梳理红层与丹霞地貌概念、甘肃省的分布特征的基础上,概略回顾丹霞地貌景观的研究过程、取得的主要成果及开发利用现状,深入总结当前存在的主要问题,提出全面查清特色地质旅游资源家底、扩大优质旅游产品供给渠道,在保护前提下进行适度开发的建议,以期为当前社会经济发展服务,不断推动甘肃省生态文明建设。