Crystal-rich mass flow deposits related to the eruption of a sublacustrine silicic cryptodome (Early Permian Collio Basin, Italian Alps)     

Christoph Breitkreuz  Lucio Cortesogno  Laura Gaggero   《Journal of Volcanology and Geothermal Research》2002,114(3-4)

Sedimentological, granulometric and petrographic data are presented from a detailed study on a crystal-rich mass flow deposit, which is presumably related to the eruption of a sublacustrine cryptodome. The deposit forms a prominent intercalation in the Lower Permian Collio Formation in the Italian Alps north of Brescia. Outcrops of the 10–20-m-thick volcaniclastic deposit (Dasdana I Beds, DB) can be traced over 12 km from east to west. The DB consists of a thick, crystal-rich, sandy–gravelly lower subunit representing a sequence of amalgamated Bouma-a(b) divisions overlain by a thin, well-bedded, sandy–muddy subunit that is rich in outsize porphyritic silicic fragments. Modal and computer-aided image analyses reveal that the crystal-rich lower subunit contains up to 80% of volcanogenic crystals. Some samples contain up to 60% of porphyritic fragments, which have a phenocryst content of about 20%. The wide textural range from cryptocrystalline, poikilomosaic, to rarer medium-grained granophyric groundmass, the irregular to lensoid shapes of the porphyritic fragments, and the presence of basement and sedimentary clasts suggest that the DB originated from a sublacustrine eruption of a partially extrusive cryptodome (ca. 1.6 km³). Two other porphyritic felsic cryptodomes (Dosso dei Lupi, Dosso del Bue), described briefly here, emplaced into the Collio Formation sometime after the DB event, and expose flat bases and tilted sediments at their sides. Textures observed in these domes are comparable to those found in the DB porphyritic fragments.  相似文献   

MODIFIED MASS FLUX CUMULUS CONVECTIVE PARAMETERIZATION SCHEME AND ITS SIMULATION EXPERIMENT—PART Ⅰ:MASS FLUX SCHEME AND ITS SIMULATION OF THE 1991 FLOOD EVENT^*          下载免费PDF全文

LIU Yiming  DING Yihui 《Acta Meteorologica Sinica》2002,16(1):37-49

Based on the existing cumulus convective parameterization schemes,a mass flux scheme (MFS) for cumulus convective parameterization has been successfully developed by reference to the work of Chen et al. (1996).The MFS is a comprehensive scheme.In MFS,not only the importance of the large-scale moisture convergence is taken into account,but also it includes the cumulus updrafts and downdrafts,cumulus-induced subsidence in the environmental air.entrainment,detrainment and evaporation.The interaction between the cumulus and the environment is described by using a one-dimensional bulk model.At the same time the scheme includes the penetrative and shallow convections.The MFS has been successfully incorporated into the regional climate model RegCM2 developed by NCAR.The new model has been applied to simulate summer monsoon characteristics and their variations of heavy rainfall process in the Changjiang-Huaihe River Basins for three months from May to July 1991.The results show that the new model can successfully simulate this rainfall prolonged process.By comparising the model outputs of RegCM2.using the Kuo scheme and the MFS.it is found that the MFS is better in simulating the surface temperature,rainfall position and amount,and rainfall duration.  相似文献   

Determining gaseous composition of fluid inclusions with quadrupole mass spectrometer   总被引：3，自引：0，他引：3  

朱和平  王莉娟 《中国科学D辑(英文版)》2002,45(2):97-102

Quadrupole mass spectrometer (QMS) is an instrument for effectively determining gaseous composition of fluid inclusion. The gaseous component is extracted from inclusions with thermal decrepitation method and then determined with the sensitive QMS instrument. The method is characterized by high sensitivity and high accuracy with the relative standard deviation (RSD,n=6) of less than 3%. It has been successfully used for analyzing fluid inclusions. The analytical results meet the requirement of geological study.  相似文献   

层控夕卡岩型矿床成矿系统的元素活动性及质量迁移--以铜陵冬瓜山铜矿床为例   总被引：7，自引：0，他引：7  

凌其聪  刘丛强 《矿物学报》2003,23(1):37-44

应用改善了的质量平衡方程研究冬瓜山层控夕卡岩型铜矿床成矿系统的元素活动性及质量迁移，结果表明：系统中Zr,Hf,Y和Nb为不活动元素，其余均为活动元素。主量元素中仅CaO为迁出组分，其质量迁移量为84％，其余均为带入组分，带入量最大的SiO2的质量迁移量高达2384％；稀土元素均为带入组分，其中，中稀土较轻稀土和重稀土的活动性更强；其它微量元素中，带入序列由强到弱为：Cr→Ta→Sn→Th，迁出序列由强至弱依次为：U→Sb→Ni—Sr→Ba→Bb→Co→W；成矿元素Cu和Ag为带入组分，其中Cu的带入量最大，质量迁移量高达1200％。本文还得出两点具普适性认识：①稀土元素较其它微量元素对体系条件的变化更为敏感，且往往表现出明显的规律性变化，能更好地示踪地质地球化学过程。②不同元素在不同体系中的行为特征差异极大，仅凭经验判定某一元素为不活动元素往往不可靠。因此，在开展质量平衡研究时，首先采用适当方法确认体系的不活动元素是一项不可或缺的前提工作。  相似文献   

热害矿井巷道温度场分布规律研究   总被引：8，自引：0，他引：8  

张树光  孙树魁  张向东  薛强 《中国地质灾害与防治学报》2003,14(3):9-11

为解决深部开采带来的热害问题，基于地质学和热力学理论，建立了热害矿井巷道温度场的数学模型，研究了巷道内部温度场随埋深和通风热速的变化规律。计算结果表明，巷道温度场对埋深的敏感度要高于风速、温度随埋深的增加而呈阶段性递增。控制入口温度是解决矿井热害的关键。以上结论为矿井热害的综合治理提供了重要依据。  相似文献   

碱熔沉淀-等离子体质谱法测定地质样品中的多元素   总被引：14，自引：17，他引：14       下载免费PDF全文

王蕾  何红蓼李冰 《岩矿测试》2003,22(2):86-92

采用过氧化钠焙融或偏硼酸锂熔融分解样品，将提取液碱性沉淀，通过过滤分离掉大量熔剂，再将沉淀用酸复溶后用等离子体质谱测定26个元素。通过对比，偏硼酸锂熔融—酸提取—碱性沉淀的方案，空白低，易操作，成本低，大多数元素测定结果的相对误差＜10％，相对标准偏差＜5％(n＝10)，与标准值相吻合。  相似文献   

乙醇增强—电感耦合等离子体质谱法直接测定地质样品中碲   总被引：9，自引：3，他引：9       下载免费PDF全文

韩丽荣李冰  马新荣 《岩矿测试》2003,22(2):98-102

建立了HF—HN03密封酸溶以及Na2O2熔融处理样品，乙醇增强灵敏度，电感耦合等离子体质谱直接测定地质样品中微量和超痕量碲的方法。样品溶液中加入乙醇(φ＝4％)，在0．85L/min的载气流速下，碲信号可增强2．5倍以上。碲的方法检出限(100，DF＝1000)为0．02μg/g。用土壤和水系沉积物国家一级标准物质验证了方法的准确度，标准物质的绝大多数分析结果与标准值的误差在允许范围内。分析了大洋多金属结核样品及深海沉积物样品中的微量碲，结果与其他方法相符，精密度试验RSD(n＝3)＜10％。  相似文献   

高温密闭溶样电感耦合等离子体质谱准确测定辉钼矿铼-锇地质年龄   总被引：176，自引：28，他引：176  

屈文俊  杜安道 《岩矿测试》2003,22(4):254-257262

采用Carius管高温密闭溶样,电感耦合等离子体质谱(ICP MS)法对采自两个不同金属矿床的辉钼矿样品的Re Os同位素地质年龄进行了准确测定。所得出的Re Os年龄的平均值分别为14.26±0.19Ma和34.39±0.81Ma,相对标准偏差分别为1.3%(以2s计算,n=6)和2.4%(以2s计算,n=7)。采用国际通用的ISOPLOT软件按Model1模式对这两组样品分别进行处理,所得Re Os等时线年龄分别为14.32±0.46Ma和34.52±0.38Ma(均为95%置信水平)。同批次样品中所带的内部管理样JDC的Re Os年龄与国际先进实验室采用负离子热表面电离质谱测量所得的结果吻合也较好。说明在严格的质量体系保证及有效地降低实验室空白水平的前提下,ICP MS完全可以准确地测定辉钼矿的Re Os年龄。  相似文献   

Fluid mixing as the mechanism of formation of the Dajing Cu-Sn-Ag-Pb-Zn ore deposit,Inner Mongolia ——Fluid inclusion and stable isotope evidence   总被引：2，自引：0，他引：2  

刘伟  李新俊  谭骏 《中国科学D辑(英文版)》2003,46(7)

Since the 1990s, interest in the magmatic fluids and their relation to mineralization has been re-aroused[1—6]. Studies on stable isotopes of low-sulfidation deposits commonly show the predominance of meteoric water[7]. Paradoxically, the evidence for me…  相似文献   

Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parameters     

Chunxiang Li  Yanxia Liu 《地震工程与结构动力学》2003,32(5):671-690

The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1～US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献