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41.
大别山碧溪岭地区超高压变质岩构造分析 总被引:7,自引:1,他引:7
大比例尺 (1∶10 0 0 0 )构造制图及构造分析表明 ,碧溪岭地区超高压变质岩石含有丰富的构造演化历史记录。同碰撞或挤压组构只保留于榴辉岩及其它超高压变质岩透镜体内部 ,表现为高角度网络状超高压剪切带与弱应变透镜体域规律组合格式。前者由面理或糜棱岩化榴辉岩组成 ,后者由块状榴辉岩及石榴橄榄岩组成。碰撞期后伸展构造表现为区域性的假单斜状 ,内部呈低缓角度的网络状强应变带及所环绕的透镜状弱应变域组合格式 ,强应变带的岩石为由榴辉岩退变成的角闪岩相高压片麻岩及部分熔融形成的含榴花岗岩 ,透镜状弱应变域的岩石为弱角闪相改造的榴辉岩及石榴橄榄岩。不同尺度上同碰撞或挤压组构及碰撞期后伸展组构所显示的这种残斑基质流变学结构样式 ,虽然与先期原岩成分、结构、流变学的不均一性有关 ,但主要是多期递进应变分解作用的结果 ,支持榴辉岩“原地”成因模式。依据构造学证据和可利用的岩石学及同位素年代学资料 ,分析了超高压变质岩石的形成及折返过程 ,指出碧溪岭地区超高压变质岩石是在 2 45~ 2 10Ma形成的 ,碰撞期后伸展作用主要发生在 2 0 0~ 170Ma。在超高压变质岩石向地壳表层折返过程中 ,张扭作用可能有重要功能 ,不支持碧溪岭地区遭受过多期超高压变质作用的推论。 相似文献
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Wang Siyuan Xiao Qibing Zeng Jianguo Faculty of Earth Resources China University of Geosciences Wuhan 《中国地质大学学报(英文版)》2001,12(1)
-,The well-known Suichang silvengold field is located inZhejiang Province of SOutheast China. It is the largest silver-gold deposit associated with copper and zinc in the Cathaysianmetallogenic province.There are a series of silver-gold dePOsits in the shear zonesof Proterozoic gneiss terrene, Suichang region. The volcanicapparatus at Mesozoic has complicated rpineralization. Respectively, there are two pieces of understanding on the origin ofore-formigg nuid: (l ) metamorphic fluid (Lia… 相似文献
45.
刘家坪杂岩体出露于扬子准地台西北边缘。该区扬子期岩浆活动,早期为刘家坪组海底喷发的中~酸性火山岩系,晚期先后侵入有角闪辉长岩—石英闪长岩—斜长花岗岩—辉绿岩脉。岩浆岩具有幔源岩浆及造山带地区火山岩的特征。据震旦系覆于刘家坪杂岩体之上,其底部砂砾岩的砾石中有杂岩体成分,以及杂岩体侵入于同位素年龄值为6.43亿年的刘家坪组之中,认为刘家坪杂岩体时代为前震旦纪。 相似文献
46.
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),... 相似文献
47.
Xue Zhang Zhongwu Li Guangming Zeng Xiaolan Xia Lin Yang Jiajie Wu 《Environmental Earth Sciences》2012,67(6):1725-1734
Erosion can have a significant impact on soil properties in areas characterized by undulating topography. The spatial trends of soil properties and the availability of soil nutrients change with land use conversion. Most studies on these changes in China, however, focus on the natural or agricultural ecosystems. Little attention has been paid to unique changes, such as the conversion of natural or agricultural land to economic development zones. To this end, it has been determined that the properties of the surface soil in an economic development zone with unique topography characterized by large mounds of earth and stones in the red soil hilly region in China. The aim of this study is to characterize the overall level and spatial patterns of the concentrations of topsoil selected soil properties, including pH, cation exchange capacity (CEC), bulk density, soil moisture, soil organic carbon (SOC), soil nitrogen (N), soil phosphorus (P), and soil potassium (K). Results show that the mean pH and CEC of soils is as low as 5.35 and 6.47?cmol?kg?1, and the mean value of soil moisture is 0.30?g?g?1, and the mean level of bulk density is 1.45?g?cm?3. SOC and total P are as low as 5.89 and 0.35?g?kg?1, while total N and total K have a high level of 8.44 and 25.2?g?kg?1. The mean level of alkali-hydrolyzable N, Olsen P, and available K is 54.33, 6.35, and 120.33?mg?kg?1, respectively, all at intermediate or low levels according to the Second National Soil Survey. All selected soil properties and nutrients have overall similar spatial patterns with the highest value on the lower slope positions except for alkali-hydrolyzable N. The results are most likely governed by the native properties of red soil, zonal climate, agricultural history for all the soils, and different degrees of soil erosion, and the probable impact of human activity like construction among different slope positions. Results indicate that (1) topography influences soil properties, as evidenced by the different spatial trends of the soil nutrients, and (2) human activity, especially construction, affects the soil properties of economic development zones. This study aims to provide valuable insights for the evaluation of soil quality as a prerequisite for land use planning in economic development zones. 相似文献
48.
Geology and geochronology of the Xilamulun molybdenum metallogenic belt in eastern Inner Mongolia,China 总被引:1,自引:0,他引:1
Qingdong Zeng Jianming Liu Zuolun Zhang Weijun Chen Weiqing Zhang 《International Journal of Earth Sciences》2011,100(8):1791-1809
The Xilamulun molybdenum metallogenic belt, located in eastern Inner Mongolia, China, has great economic potential as a major
producer of molybdenum. Four major types of Mo deposits have been recognized in the Xilamulun molybdenum metallogenic belt:
porphyry, quartz vein, volcanic-hosted, and greisen. These Mesozoic Mo deposits are closely related to Si- and K-rich intrusives
and are usually hosted by granite plutons or located at the endo- or exo-contact zones of the granite porphyry. SHRIMP zircon
U–Pb dating gives the emplacement ages of the intrusions related to Mo mineralization as 245.1 ± 4.4, 152.4 ± 1.6, and 139.1 ± 2.3 Ma.
Re–Os analysis of five molybdenite samples from the Chehugou porphyry Mo deposit yields an isochron age of 245 ± 5 Ma (2σ),
indicating that the mineralization age of the porphyry Mo deposit is about 245 Ma. Re–Os analyses of six molybdenite samples
from the Nianzigou quartz-vein-type Mo deposit yield an isochron age of 154.3 ± 3.6 Ma (2σ), constraining the mineralization
age of the quartz-vein Mo deposit to 154 Ma. Our results suggest that the Mo mineralization in the Xilamulun belt formed during
at least three stages, i.e., the Triassic, Late Jurassic, and Early Cretaceous, and is coeval with the granitic magmatism.
The corresponding geodynamic background covers the syncollision between the North China and Siberian plates during the Early
to Middle Triassic, a compression setting related to the subduction of the Paleo-Pacific plate during the Jurassic and lithospheric
thinning during the Early Cretaceous in eastern China. 相似文献
49.
Spatial distribution of surface soil water content under different vegetation types in northwest Guangxi, China 总被引:2,自引:1,他引:2
Wanxia Peng Tongqing Song Fuping Zeng Kelin Wang Hu Du Shiyang Lu 《Environmental Earth Sciences》2013,69(8):2699-2708
Geostatistical and statistical analyses were combined to examine the spatial distribution of soil water content under four vegetation types during the dry season, in the peak-cluster depression in the karst region in northwest Guangxi, southwest China. The soil water content significantly increased from farmland to plantation, secondary forest, and primary forest; whereas the variation coefficients, the sill (C 0+C), and total spatial variance increased, although the range decreased. The spatial distribution of soil water content in the different vegetation types had a high spatial autocorrelation. Different models produced a best fit for the semivariograms of the four vegetation types. Elevation and slope position were the primary factors influencing the spatial distribution of soil water content, with other key factors differing between the four vegetation types. Moreover, even though different specific factors influenced soil water content in the four vegetation types, the correlations and degrees of associations between the soil water content and these various factors differed. Therefore, the corresponding strategies for rational usage and management of water resources should be different for the four vegetation types in this region. 相似文献
50.
Biomarkers in the Molar Tooth (MT)-Bearing Limestones in the Jilin-Liaoning Area of China 总被引:2,自引:1,他引:2
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. 相似文献