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Paul T.ROBINSON 《《地质学报》英文版》2001,75(1):41-50
The Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. The diabases and basalts show light rare-earth element enrichment and have relatively high TiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. They are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr-spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proteroz 相似文献
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Peter Bajto 《岩石学报》2004,20(4)
Dubravsky Massif菱镁矿体的开采产生了部分局限在石炭纪低裂缝渗透变质岩中的喀斯特型裂缝含水层。大量的开矿过程对含水层中的地下水循环和化学成分都造成了可观的变化。本文研究了在这种复杂条件下地下水化学成分变化成因模型。根据化学配位模型,计算出所选矿物的饱和指数,从而指示所有喀斯特裂缝含水层饱和带中的地下水对菱镁矿、白云石、方解石的过饱和度和石膏的不饱和度。假设地下水未受人类活动的污染,而白云石中黄铁矿的氧化对成矿影响甚微,则水化学数据的统计描述代表了含水层中的水文地球化学背景。矿山中矿石焙烧释放的富氮气体凝聚产生的醋酸,能促进菱镁矿和白云石的溶解。这样产生的地下水相对背景值来说则富集NO3,Mg,和TIC。因此,由于地下开矿,岩溶作用估计将是原来的1.5倍。尽管有污染,这些所测参数并没有超过斯洛伐克卫生保健部颁发的No.29／2002 Z.z.饮用水标准临界值。因此采矿后含水层的开采也是可行的。 相似文献
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Santiago Hincapié-Gómez Agustín Cardona Giovanny Jiménez Gaspar Monsalve León Ramírez-Hoyos Germán Bayona 《Studia Geophysica et Geodaetica》2018,62(3):485-511
The reconstruction of the tectonic evolution of the oceanic crust, including the recognition of ancient oceanic plumes and the differentiation between multiple and single oceanic arcs, relies on the paleogeographic analysis of accreted oceanic fragments found in orogenic belts. Here we present paleomagnetic and gravity data from Cretaceous oceanic basaltic and gabbroic rocks, the continental metamorphic basement, and their associated cover from northwestern Colombia. Based on regional scale tectonic reconstructions and geochemical constraints, such rocks have been interpreted as remnants of an oceanic large igneous province formed in southern latitudes, which was accreted to the sialic continental margin during the Late Cretaceous. Gravity analyses suggest the existence of a coherent high density segment separated by major suture zones from a lower density material related to the continental crust and/or thick sedimentary sequences trapped during collision. A characteristic paleomagnetic direction in Early and Late Cretaceous oceanic volcano-plutonic rocks, revealing a southeastern declination (D) and a negative inclination (I), may be interpreted in two different ways: (1a primary magnetization (tilt-corrected direction D = 130.3°, I = -23.3°, k = 23.4, α95 = 26.4°), suggesting clockwise rotation around 130°, and magnetization acquired in southern latitudes (range of 4°S to 21°S); or (2) a remagnetization event during a reverse interval of the Earth’s magnetic field in the Cenozoic (in situ direction D = 128.7°, I = -6.2°, k = 23.1, α95 = 26.1°), suggesting a counter-clockwise rotation around 50°. The first scenario seems more plausible, as it is consistent with previous paleomagnetic studies at other localities; it is compatible with a southern paleogeography for this block, and when integrated with other regional geological and paleomagnetic studies, supports a southern Pacific origin of a major oceanic block, formed as a part of a broader Cretaceous plateau that may have extended south or southwest of Galapagos. After its initial accretion, this block was subsequently fragmented due to the oblique SW-NE approach to the continental margin during the Late Cretaceous. 相似文献
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Combined use of isotopic and hydrometric data to conceptualize ecohydrological processes in a high‐elevation tropical ecosystem 
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下载免费PDF全文 Giovanny M. Mosquera Rolando Célleri Patricio X. Lazo Kellie B. Vaché Steven S. Perakis Patricio Crespo 《水文研究》2016,30(17):2930-2947
Few high‐elevation tropical catchments worldwide are gauged, and even fewer are studied using combined hydrometric and isotopic data. Consequently, we lack information needed to understand processes governing rainfall–runoff dynamics and to predict their influence on downstream ecosystem functioning. To address this need, we present a combination of hydrometric and water stable isotopic observations in the wet Andean páramo ecosystem of the Zhurucay Ecohydrological Observatory (7.53 km2). The catchment is located in the Andes of south Ecuador between 3400 and 3900 m a.s.l. Water samples for stable isotopic analysis were collected during 2 years (May 2011–May 2013), while rainfall and runoff measurements were continuously recorded since late 2010. The isotopic data reveal that andosol soils predominantly situated on hillslopes drain laterally to histosols (Andean páramo wetlands) mainly located at the valley bottom. Histosols, in turn, feed water to creeks and small rivers throughout the year, establishing hydrologic connectivity between wetlands and the drainage network. Runoff is primarily composed of pre‐event water stored in the histosols, which is replenished by rainfall that infiltrates through the andosols. Contributions from the mineral horizon and the top of the fractured bedrock are small and only seem to influence discharge in small catchments during low flow generation (non‐exceedance flows < Q35). Variations in source contributions are controlled by antecedent soil moisture, rainfall intensity, and duration of rainy periods. Saturated hydraulic conductivity of the soils, higher than the year‐round low precipitation intensity, indicates that Hortonian overland flow rarely occurs during high‐intensity precipitation events. Deep groundwater contributions to discharge seem to be minimal. These results suggest that, in this high‐elevation tropical ecosystem, (1) subsurface flow is a dominant hydrological process and (2) (histosols) wetlands are the major source of stream runoff. Our study highlights that detailed isotopic characterization during short time periods provides valuable information about ecohydrological processes in regions where very few basins are gauged. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Gemerská Poloma矿床是个重要的滑石矿床(储量20万吨),位于西喀尔巴阡山脉Germeric地区。部分滑石化的镁质碳酸盐体赋存在早古生代火山沉积杂岩体中(黑色片岩,变质泥岩),在Variscan变质作用(M1)过程中受到了绿泥石-黑云母带区域变质相的改造。这种原岩是石灰岩的矿体由白色-灰白或者灰色-黑色的菱镁矿与白云石1组成,被次生的白云石2和滑石脉切割。本次研究考察了两次变质事件(M1和M2)的几个连续的矿物组合,最早的组合包括铁白云石,镁菱铁矿与菱铁矿,(并与黑电气石,铁绿泥石,磷灰石,与伊利石-白云母伴生),它们以微小残留物形式产出在菱镁矿和白云石1中,其形成可能早于M1变质作用高峰期。M1变质事件的高峰期以富铁金云母,镁绿泥石1,镁电气石(黑电气石的边缘)和石英的组合为代表。在M1退变质作用过程中,发生了镁交代作用,开始是白云石1结晶,接下来形成菱镁矿,最后是以铁菱镁矿沿裂隙的形成而终。根据碳酸盐地质测温原理,M1变质事件的高峰期温度为460~490℃,变质矿物组合特征也支持这一测温结果。滑石,白云石2,与镁绿泥石2沿着镁碳酸盐岩石裂隙的发育,主要受到M2变质事件的影响,这个变质事件与较年青的Alpine造山事件有关。 菱镁矿流体包裹体的研究表明,成矿流体具有复杂的组成,可能以MgCl2组分为主,主要来 相似文献
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Kosice矿床是斯洛伐克第二大的菱镁矿床(150Mt),位于Gemeric的东部。其镁质碳酸盐矿体赋存于石炭纪石灰石和含白云石的石灰石中,同时下盘黑色片岩中也含有被铁质碳酸盐交代的薄层碳酸盐透镜体。在华力西期造山运动(M1)中,古生代岩石受到了低级变质作用(绿泥石带)。镁交代作用始于白云岩1的结晶作用,其后形成菱镁矿,最终沿裂隙形成铁菱镁矿。铁质碳酸盐包括早期铁白云石-白云石,铁白云石和后期含方解石和石英的菱铁矿。根据碳酸盐矿物对地质温度计,白云石1结晶作用发生在300~340℃。这一结果与M1的变质矿物组合(绿泥石,白云母-伊利石)吻合。铁白云石的结晶作用发生在320~370℃.少量细脉中可见白云石2,绿泥石和伊利石-多硅白云母,它们是由于阿尔卑斯期造山运动M2变质作用形成的更晚的矿物组合。 菱镁矿的流体包裹体(FI)研究,显示存在不同成分的热卤水,卤水成分变化相当于NaCl含量21~42wt％,但其它成分的盐含量高于NaCl,溶解的CO2含量也有变化。两相包裹体均一温度(Th)的范围为164~217℃,含石盐子晶包裹体均一温度的范围为217~344℃。富CO2包裹体(盐度相当于NaCl含量1-22wt％,CO2的密度为0.28~0.77 g·cm-3,均一温度为289~344℃)在菱镁矿中是次要的,但这种包裹体在与矿石伴生的石英中是主要的,并且与含石盐 相似文献
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Kamae P. Anacioco Judy Ann L. Gorio Mary Relia S. Padsico Roscinto Ian C. Lumbres Nova D. Doyog Young Jin Lee 《山地科学学报》2018,15(11):2422-2432
The study was conducted to develop height-diameter at breast height (HT-DBH) models for Alnus japonica in La Trinidad, Benguet, Philippines and evaluate their predictive capability. The six widely used nonlinear growth models that were selected in this study were the Chapman-Richards, Schnute, Modified logistic, Korf/Lundqvist, Weibull and Exponential. A total of 208 Alnus japonica trees were measured using standard diameter tape for DBH (1.3 m above the ground) and Vertex and transponder was used for the total height measurement. The performance of the developed models were evaluated using the fit statistics including coefficient of determination (R2), root mean square error (RMSE), mean bias (ē), absolute mean difference (AMD), and Akaike Information Criterion (AIC). The lack-of-fit statistics was also performed for further evaluation of the performance of the models. Based on the evaluation criteria, all six models were able to determine the DBH-height relationships and fitted the data well. Using the rank analysis, the Weibull HT-DBH model had the best performance among the six commonly used nonlinear growth models. The results of this study will help forest managers especially in La Trinidad, Benguet to easily predict the total height using the Weibull model for Alnus japonica utilizing the DBH as the predicting variable. 相似文献
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Giovanny M. Mosquera Marín Franklin Feyen Jan Célleri Rolando Breuer Lutz Windhorst David Crespo Patricio 《水文研究》2021,35(1):e14011
Accurate determination of the water retention curve (WRC) of a soil is essential for the understanding and modelling of the subsurface hydrological, ecological, and biogeochemical processes. Volcanic ash soils with andic properties (Andosols) are recognized as important providers of ecological and hydrological services in mountainous regions worldwide due to their large fraction of small size particles (clay, silt, and organic matter) that gives them an outstanding water holding capacity. Previous comparative analyses of in situ (field) and standard laboratory methods for the determination of the WRC of Andosols showed contrasting results. Based on an extensive analysis of laboratory, experimental, and field measured WRCs of Andosols in combination with data extracted from the published literature we show that standard laboratory methods using small soil sample volumes (≤300 cm3) mimic the WRC of these soils only partially. The results obtained by the latter resemble only a small portion of the wet range of the Andosols' WRC (from saturation up to −5 kPa, or pF 1.7), but overestimate substantially their water content for higher matric potentials. This discrepancy occurs irrespective of site-specific land use and cover, soil properties, and applied method. The disagreement limits our capacity to infer correctly subsurface hydrological behaviour, as illustrated through the analysis of long-term soil moisture and matric potential data from an experimental site in the tropical Andes. These findings imply that results reported in past research should be used with caution and that future research should focus on determining laboratory methods that allow obtaining a correct characterization of the WRC of Andosols. For the latter, a set of recommendations and future directions to solve the identified methodological issues is proposed. 相似文献
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