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991.
土壤铁锰结核中生命有关元素的化学地理特征 总被引:11,自引:1,他引:11
研究了我国亚热带、暖温带几种土壤铁锰结核中锰矿物的类型,探讨了它们形成的地球化学过程与特征。结果表明:不同土壤铁锰结核锰矿物的类型及其含量不尽相同,但锂硬锰矿普遍存在且结晶程度较高;与土壤相比,土壤铁锰结核的化学组成仍以Si、Al、Fe为主,但Fe含量超过了Al,Mn含量远大于Mg、Ca;结核中一些重金属富集顺序为Pb>Co>Ni>Cu>Zn>Cr;揭示了土壤铁锰结核形成过程中存在着成核富集作用、成矿作用、专性吸附作用和轻度积钙作用。 相似文献
992.
R. K. Lal 《Journal of Earth System Science》1997,106(3):91-113
Sixty-three internally consistent geothermobarometers for mineral equilibria involving sapphirine (2:2:1 and 7:9:3), pyrope,
cordierite, enstatite, Mg-tschermak orthopyroxene, quartz, spinel and sillimanite have been calibrated in the MAS system.
The updated thermodynamic data of these minerals are consistent, within limits of error, with highP-T experiments on several mineral equilibria and calorimetric data. TheP-T conditions of the granulite facies metamorphism, spanning a range of 700 to more than 1000°C and 4 to more than 10 kbar,
can be estimated simultaneously from these geothermobarometers andP-T-t trajectories can be deduced from the reaction coronas well preserved in these rocks because of the refractory nature of aluminous
phases.
The geothermobarometers have been applied to sapphirine-spinel granulites of Eastern Ghats and Enderby Land. TheP-T conditions of metamorphism (a-prograde/thermal peak and b-retrograde isothermal/isobaric decompression/cooling) estimated
for these granulites are: (1) Eastern Ghats (Visakhapatnam): Paderu- (a) 900°C/8.3kbar, (b-1) 900°C/6.8kbar and (b-2) 740°C/5.4
kbar; Anantgiri- (a) prograde anticlockwise 930°C/6.2 kbar and (b) 870°C/6.8 kbar, 820°C/6.1 kbar; Anakapalle- (b) 845°C/8.5-6.2
kbar; and Araku- (b) 840°C/6.2 kbar to 795°C/5.9 kbar. Enderby Land (Napier complex): Spot height 945, Tula Mts.- (a) 970°C/9.1
± 0.6 kbar, isobaric cooling (b) 885°C/ 7.75 kbar, isothermal decompression (b) 880°C/6.85 kbar; Mt. Hardy, Tula Mts.- (b)
885°C/6.75 kbar; Mt. Riiser-Larsen, Amundsen bay- (a) 1000°C/7.0 kbar prograde anticlockwise; Mt. Sones- (b) 920°C/ 6.8 kbar;
Forefinger Point, SW Enderby Land- (b) 840°C/6.7 kbar, 810°C/6.5 kbar and 775°C/5.0 kbar. The estimatedP-T andP-T-t are mostly consistent with those inferred from the granulites of these areas. 相似文献
993.
994.
995.
1994-04以后,国务院规定矿床工业指标由矿产储量审批机构统一下达,从历史的经验和现实的管理来看都是十分重要的。本文介绍了矿床工业指标制定与管理的原则,程序和方法,以及湖南省储委的5点经验,并提出了加强这一工作的建议。 相似文献
996.
着重论述了丁家山铅锌(银)矿床的地质地球物理特征,磁法找矿的特殊作用,总结了建筑梅仙式矿床的物化探异常标导。 相似文献
997.
乌拉山金矿钾长石的标型性及其与金矿化关系 总被引:6,自引:0,他引:6
在对乌拉山石英-钾长石脉型这一国内外尚不多见的新类型金矿床的野外观察和室内镜下研究的基础上,通过选择性地对其主要矿物钾长石进行电子探针分析,X射线粉晶衍射分析,红2外吸收光谱测定及可见光吸收光谱分析,系统详尽地了钾长石的产状,形态,化学成分,结构态及可见光吸收光谱特征,提取了作为找寻石英-钾长石脉型金矿床的重要矿物学标志,并进一步探讨了钾长石与金矿化的关系。 相似文献
998.
In order to determine whether it is desirable to quantify mineral-deposit models further, a test of the ability of a probabilistic
neural network to classify deposits into types based on mineralogy was conducted. Presence or absence of ore and alteration
mineralogy in well-typed deposits were used to train the network. To reduce the number of minerals considered, the analyzed
data were restricted to minerals present in at least 20% of at least one deposit type. An advantage of this restriction is
that single or rare occurrences of minerals did not dominate the results. Probabilistic neural networks can provide mathematically
sound confidence measures based on Bayes theorem and are relatively insensitive to outliers. Founded on Parzen density estimation,
they require no assumptions about distributions of random variables used for classification, even handling multimodal distributions.
They train quickly and work as well as, or better than, multiple-layer feedforward networks. Tests were performed with a probabilistic
neural network employing a Gaussian kernel and separate sigma weights for each class and each variable. The training set was
reduced to the presence or absence of 58 reported minerals in eight deposit types. The training set included: 49 Cyprus massive
sulfide deposits; 200 kuroko massive sulfide deposits; 59 Comstock epithermal vein gold districts; 17 quartzalunite epithermal
gold deposits; 25 Creede epithermal gold deposits; 28 sedimentary-exhalative zinc-lead deposits; 28 Sado epithermal vein gold
deposits; and 100 porphyry copper deposits. The most common training problem was the error of classifying about 27% of Cyprus-type
deposits in the training set as kuroko. In independent tests with deposits not used in the training set, 88% of 224 kuroko
massive sulfide deposits were classed correctly, 92% of 25 porphyry copper deposits, 78% of 9 Comstock epithermal gold-silver
districts, and 83% of six quartzalunite epithermal gold deposits were classed correctly. Across all deposit types, 88% of
deposits in the validation dataset were correctly classed. Misclassifications were most common if a deposit was characterized
by only a few minerals, e.g., pyrite, chalcopyrite,and sphalerite. The success rate jumped to 98% correctly classed deposits
when just two rock types were added. Such a high success rate of the probabilistic neural network suggests that not only should
this preliminary test be expanded to include other deposit types, but that other deposit features should be added 相似文献
999.
Offset of prograde hydrothermal alterations by retrograde reactions is evident in sediments from a piston core (PC6, 8 m long) from the Guaymas Basin, Gulf of California. Geochemical and mineralogical analyses of sediments and pore fluids show superimposed geochemical signals that indicate currently active reactions are modifying previously formed secondary solids. Hydrothermal barite was formed in a previously active flow channel between 150 and 250 cm depth. Hydrothermal gypsum is presently dissolving at depths > 780 cm, below which hydrothermal fluid flow is channeled by a secondary dolomite layer. Thermal stress of organic matter generates hydrothermal gas and petroleum having wide ranges of compositions and maturities. A significant amount of hydrothermally generated oil has been transported laterally through a porous debris flow (approx. 240 cm subbottom), overwhelming the indigenous bituminous matter. Water soluble petroleum constituents have disseminated throughout the cored sediments. From 400 to 700 cm depth the immature organic matter continues to experience thermally-enhanced diagenesis, and an even higher thermal stress has occurred at the bottom of the core. Enhanced bacterial degradation of organic matter has led to depletion of pore water sulfate and enrichment of ammonium (NH4+) in both pore fluid and sediment, resulting in formation of NH4+ bearing secondary clay minerals at depths below 780 cm. 相似文献
1000.
主要介绍我所30年来,在基性、超基性岩及有关矿产研究方面的基本概况、取得的进展及今后一些展望。其中所列进展主要包括:岩浆矿床学、岩石及成因学、岩浆建造学及矿床评价和预测等四个方面的研究。 相似文献