东准噶尔蒙西斑岩铜钼矿床脉体特征及其形成机制

蒙西斑岩铜钼矿床位于东准噶尔伊吾县琼河坝花岗岩北侧,以发育细脉、网脉状矿化为特征。脉体类型多样,包括石英脉、石英硫化物脉和硫化物脉等。根据脉体力学成因机制,其又可划分为水压破裂充填脉和构造破裂充填脉。构造破裂充填脉体按破裂形成的位错特征有正断与逆断两种。地表石英脉产状陡立,明显受断裂控制。脉体体积分数统计结果显示流体富集区呈向北缓倾的带状分布于深100～400m范围内,并与矿化富集带有较好的对应关系。脉体富集带内,脉体以共轭形式存在,一组为倾角较小的逆断破裂充填脉,另一组为倾角较大的正断破裂充填脉,他们可能为缓倾逆冲剪切带的次级破裂与充填脉,即富矿带内脉体是沿矿区低角度逆冲断裂次级破裂面充填的。矿区地表及深部(400m以下)脉体以陡立为主,矿化较弱。矿区流体的运移具先沿水压直立破裂往上运移,进入剪切带后沿剪切带次级破裂侧向和向上运移,并在剪切带中富集成矿。低温矿物组合脉体穿切高温矿物组合脉体的特征说明脉体形成过程矿区处于隆升构造环境,这对斑岩铜矿成矿有利。     

Morphological indicators of structural control,relative sea-level fluctuations and platform drowning on present-day and Miocene carbonate platforms

The morphology of Carbonate platforms may be influenced by tectonic activity and eustatic variations. 3D seismic data and satellite imagery are used in order to investigate the morphological similarities between present-day carbonates platforms, East of Borneo Island and Miocene carbonate platforms of the South China Sea. The morphological similarities exhibit platform fragmentation, that could be caused by subtle faulting, sufficient to drown reef rims; platform contraction, which is a result of back-stepping of the reef margin during a relative sea level rise and polygonal patterns in internal lagoons, described as mesh reefs in modern platforms and possibly interpreted as karst in Miocene platforms.Vertical movements may trigger the formation of new geomorphological conditions that modify the distribution of coral growth with respect to the new hydrodynamic conditions in space and time. These movements (uplift and tilting) reduce and localize the space necessary for the coral ecosystem, explaining the contraction leading to drowning of parts of and, ultimately, the whole platform.     

定向岩芯构造分析及在金矿勘查中的运用

系统测量定向岩芯中构造面的α角和β角,结合钻孔的方位角和钻孔倾角,通过赤平投影可以还原真实的构造面产状.通过穿过金矿体的定向岩芯的构造编录和系统分析,计算矿体中的主要含矿节理、含矿蚀变带等构造面的产状,并进行统计分析,可以了解矿化与各类构造之间的关系,计算矿体的空间产状,并推断主矿体的延伸等,为矿区的深部勘查设计提供依据.     

山东大地构造相研究方法划分方案与基本特征

在系统收集山东已完成的1∶5万、1∶20万和1∶25万区域地质资料基础上,通过编制山东省1∶25万实际材料图和建造构造图、1∶50万大地构造相五要素工作底图和1∶50万大地构造相图,全面介绍了大地构造相的定义、研究内容、指导思想、基本原则与编图程序。采用大地构造相编图作为大陆动力学研究的主要方法,是揭示不同陆块之间相互作用、形成过程和演化历史、研究山东大陆块体离散、会聚、碰撞、造山的大陆动力学过程的主要载体和具体表达形式。进而对山东大地构造相进行了划分,共划出华北陆块区、秦祁昆造山系和中国东部陆缘弧盆系相系3大相系,鲁西陆块、渤海陆块、大别苏鲁结合带、威海弧盆系、胶辽岩浆弧和华北裂谷盆地6个大相以及20个相和59个亚相,明确了其鉴别标志。对陆块区、造山系和陆缘弧盆系相系以及大相、相的基本特征进行了描述;简要总结了大地构造相与成矿尤其是金矿的关系,探讨了不同矿床与大地构造相的成因联系。     

山东省沉积岩建造组合划分

为编制1∶50万山东省大地构造相工作底图（沉积岩区）提供依据,按照沉积岩建造组合划分原则和大地构造相研究的有关要求,划分了山东省沉积岩区大地构造相和沉积岩建造组合,将山东省沉积岩区大地构造相划分为2个相系（Ⅰ级）、3个大相（Ⅱ级）、15个相（Ⅲ级）、27个亚相（Ⅳ级）及40个建造组合（Ⅴ级）,并简要介绍了主要沉积岩建造组合基本特征。     

The late Mesozoic–Cenozoic tectonic evolution of the South China Sea: A petrologic perspective

This paper presents a review of available petrological, geochonological and geochemical data for late Mesozoic to Recent igneous rocks in the South China Sea (SCS) and adjacent regions and a discussion of their petrogeneses and tectonic implications. The integration of these data with available geophysical and other geologic information led to the following tectono-magmatic model for the evolution of the SCS region. The geochemical characteristics of late Mesozoic granitic rocks in the Pearl River Mouth Basin (PRMB), micro-blocks in the SCS, the offshore continental shelf and Dalat zone in southern Vietnam, and the Schwaner Mountains in West Kalimantan, Borneo indicate that these are mainly I-type granites plus a small amount of S-type granites in the PRMB. These granitoids were formed in a continental arc tectonic setting, consistent with the ideas proposed by Holloway (1982) and Taylor and Hayes, 1980, Taylor and Hayes, 1983, that there existed an Andean-type volcanic arc during later Mesozoic era in the SCS region. The geochonological and geochemical characteristics of the volcanics indicate an early period of bimodal volcanism (60–43 Ma or 32 Ma) at the northern margin of the SCS, followed by a period of relatively passive style volcanism during Cenozoic seafloor spreading (37 or 30–16 Ma) within the SCS, and post-spreading volcanism (tholeiitic series at 17–8 Ma, followed by alkali series from 8 Ma to present) in the entire SCS region. The geodynamic setting of the earlier volcanics was an extensional regime, which resulted from the collision between India and Eurasian plates since the earliest Cenozoic, and that of the post-spreading volcanics may be related to mantle plume magmatism in Hainan Island. In addition, the nascent Hainan plume may have played a significant role in the extension along the northern margin and seafloor spreading in the SCS.     

青海东昆仑哈日扎多金属矿区构造活动的锆石裂变径迹定年分析

青海省哈日扎多金属矿区位于东昆仑东段,属东昆中多旋回岩浆弧带,是新的矿产勘查基地,成矿作用主要受NE和NW向两组构造蚀变带控制。本文通过不同类型样品的锆石裂变径迹定年分析,探讨区内的构造活动。所获得的10个样品年龄为116~204 Ma,并由3个组年龄构成,即204~181 Ma,142~168 Ma和116~120 Ma。第1组年龄204~181 Ma反映印支晚期三叠纪末羌塘地块与昆仑地块碰撞的地质事件及其时限;后两组年龄主要是晚侏罗世~早白垩世冈底斯地体向北与羌塘地体碰撞汇聚的响应,活动时限为168~116 Ma。第2和3组年龄同时表明本区燕山期构造活动存在强度差异,即有两个强作用期。同时,3组年龄也揭示本区具有多期次成矿活动。     

A paleomagnetic and magnetic fabric study of the Illapel Plutonic Complex,Coastal Range,central Chile: Implications for emplacement mechanism and regional tectonic evolution during the mid-Cretaceous

The Illapel Plutonic Complex (IPC), located in the Coastal Range of central Chile (31°–33° S), is composed of different lithologies, ranging from gabbros to trondhjemites, including diorites, tonalites and granodiorites. U/Pb geochronological data shows that the IPC was amalgamated from, at least, four different magmatic pulses between 117 and 90 Ma (Lower to mid-Cretaceous). We present new paleomagnetic results including Anisotropy of Magnetic Susceptibility (AMS) from 62 sites in the plutonic rocks, 10 sites in country rocks and 7 sites in a mafic dyke swarm intruding the plutonic rocks.Remanent magnetizations carried by pyrrhotite in deformed country rock sediments nearby the intrusive rocks indicate that tilting of the sedimentary rocks occurred prior or during the intrusion. The paleomagnetic study shows no evidence for either a measurable tilt of the IPC or a significant rotation of the forearc at this latitude range. Moreover, new ⁴⁰Ar/³⁹Ar ages exclude any medium- to low-temperature post-magmatic recrystallization/deformation event in the studied samples. AMS data show a magnetic foliation that is often sub-vertical. Despite an apparent N–S elongated shape of the IPC, the large variations in the orientation of the AMS foliation suggests that this plutonic complex could be made of several units distributed in a N–S trend rather than N–S elongated bodies.Previous works have suggested for this area a major shift on tectonic evolution from highly extensional during Lower Cretaceous to a period around 100 Ma, associated with exhumation and compressive deformation to conform the present day Coastal Range. The low degree of anisotropy and the lack of evidence for a tectonic fabric in the intrusive rocks indicate that the shift from extensional to compressional should postdate the emplacement of the IPC, i.e. is younger than 90Ma.     

Andean earthquakes triggered by the 2010 Maule,Chile (Mw 8.8) earthquake: Comparisons of geodetic,seismic and geologic constraints

The Maule, Chile, (M_w 8.8) earthquake on 27 February 2010 triggered deformation events over a broad area, allowing investigation of stress redistribution within the upper crust following a mega-thrust subduction event. We explore the role that the Maule earthquake may have played in triggering shallow earthquakes in northwestern Argentina and Chile. We investigate observed ground deformation associated with the M_w 6.2 (GCMT) Salta (1450 km from the Maule hypocenter, 9 h after the Maule earthquake), M_w 5.8 Catamarca (1400 km; nine days), M_w 5.1 Mendoza (350 km; between one to five days) earthquakes, as well as eight additional earthquakes without an observed geodetic signal. We use seismic and Interferometric Synthetic Aperture Radar (InSAR) observations to characterize earthquake location, magnitude and focal mechanism, and characterize how the non-stationary, spatially correlated noise present in the geodetic imagery affects the accuracy of our parameter estimates. The focal mechanisms for the far-field Salta and Catamarca earthquakes are broadly consistent with regional late Cenozoic fault kinematics. We infer that dynamic stresses due to the passage of seismic waves associated with the Maule earthquake likely brought the Salta and Catamarca regions closer to failure but that the involved faults may have already been at a relatively advanced stage of their seismic cycle. The near-field Mendoza earthquake geometry is consistent with triggering related to positive static Coulomb stress changes due to the Maule earthquake but is also aligned with the South America-Nazca shortening direction. None of the earthquakes considered in this study require that the Maule earthquake reactivated faults in a sense that is inconsistent with their long-term behavior.     

Tectonomagmatic origin of Precambrian rocks of Mexico and Argentina inferred from multi-dimensional discriminant-function based discrimination diagrams

Several new multi-dimensional tectonomagmatic discrimination diagrams employing log-ratio variables of chemical elements and probability based procedure have been developed during the last 10 years for basic-ultrabasic, intermediate and acid igneous rocks. There are numerous studies on extensive evaluations of these newly developed diagrams which have indicated their successful application to know the original tectonic setting of younger and older as well as sea-water and hydrothermally altered volcanic rocks. In the present study, these diagrams were applied to Precambrian rocks of Mexico (southern and north-eastern) and Argentina. The study indicated the original tectonic setting of Precambrian rocks from the Oaxaca Complex of southern Mexico as follows: (1) dominant rift (within-plate) setting for rocks of 1117–988 Ma age; (2) dominant rift and less-dominant arc setting for rocks of 1157–1130 Ma age; and (3) a combined tectonic setting of collision and rift for Etla Granitoid Pluton (917 Ma age). The diagrams have indicated the original tectonic setting of the Precambrian rocks from the north-eastern Mexico as: (1) a dominant arc tectonic setting for the rocks of 988 Ma age; and (2) an arc and collision setting for the rocks of 1200–1157 Ma age. Similarly, the diagrams have indicated the dominant original tectonic setting for the Precambrian rocks from Argentina as: (1) with-in plate (continental rift-ocean island) and continental rift (CR) setting for the rocks of 800 Ma and 845 Ma age, respectively; and (2) an arc setting for the rocks of 1174–1169 Ma and of 1212–1188 Ma age. The inferred tectonic setting for these Precambrian rocks are, in general, in accordance to the tectonic setting reported in the literature, though there are some inconsistence inference of tectonic settings by some of the diagrams. The present study confirms the importance of these newly developed discriminant-function based diagrams in inferring the original tectonic setting of Precambrian rocks.