Value of tectonic regions in the United States

Occurrence of mineral resources is directly or indirectly controlled by major tectonic processes. Additionally, similar mineral deposit types tend to be concentrated within geologically and tectonically similar areas. As a result, information on the production history of minerals in a well-explored and developed tectonic region—such as within the United States—can be used to estimate resources of geologically similar, underdeveloped tectonic areas elsewhere. For such application, two regions should be compared for geologic similarity using all available geologic information. Estimates of resources based on geologic analogy can be useful in large-scale mineral exploration programs where relatively little geologic information is available, such as in many developing countries. In this study, seven major tectonic regions within the United States are evaluated in terms of estimated mineral value as measured by historical mineral production and economic reserves. The seven regions assessed are: (1) Cordilleran Mountain Belt, (2) Colorado Plateau, (3) Central Stable Region, (4) Canadian Shield, (5) Ozark-Ouachtia Province, (6) Gulf and Atlantic Coastal Plain, and (7) Appalachian Mountain Belt. Regions are ranked in terms of estimated value of (1) 33 major mineral commodities, (2) nonfuel minerals, (3) hydrocarbons, and (4) individual mineral commodities. In terms of total value of historical mineral production and estimated economic reserve amounts of 33 major mineral commodities, the Gulf and Atlantic Coastal Plain is most valuable, with an estimated value of 1980 US$1,970,000/km². Information on historical mineral production of U.S. tectonic regions may be useful in estimating resources in tectonically similar, underdeveloped regions elsewhere.     

An evaluation of the undiscovered mineral resources of India based on the concept of unit regional value

Unit regional value (URV) and unit regional weight (URW) are relatively new concepts which are used to measure the intensity of the development of the mineral resources of any particular region. URV and URW of the mineral resources of India have been evaluated by sector, by commodity, as well as by state. The results are compared with values for the U.S.A. established by earlier workers and which can be taken as a standard for comparison with the mineral resources of other regions. URV of India, evaluated through the years 1898–1985, shows that the total mineral resources produced stands at $24.4 billion U.S. (deflated to 1967 value). Log URV of India lies below one standard deviation of the value for the states of the U.S. Like the U.S. India's major contribution to its URV is from fuels, but it is much less compared to that of the U.S. Next to fuels, metals, nonmetals, construction materials, and precious materials follow in that order. Except for two states, viz. Bihar and West Bengal, all other states are just below two standard deviations of the states of the U.S. The state of J&K is even much lower than the two standard deviations mark. It is concluded that India has a high potential for undiscovered mineral resources. However, this will require a large investment in exploration, on the order of Rs. 7760 crores, in the next few years.     

四川乐山建材非金属矿产资源的勘查与开发利用前景

概述了乐山建材非金属矿产资源的主要特征，阐明了其勘查与开发利用现状，并对资源形势作了分析，进而论述勘查与开发利用的前景。     

广西贵港六梅金矿地球化学研究

广西贵港六梅金矿床位于贵港市龙山矿田福六岭金矿区,为微细浸染型金矿床。矿床中主要矿石矿物为毒砂和黄铁矿。通过载金矿物毒砂和黄铁矿含金性、金浸出提取、晶体结构测定等方法,查明矿床的金存在形式。浸出率试验中平衡计算表明,载金矿物毒砂中的晶格金形式约占25%,超显微包体形式金约为75%。矿床流体包裹体测温和稀土元素地球化学研究表明,六梅金矿床为中-低温热液型矿床,成矿物质来源与地层有关。     

东秦岭两种新型钼矿床的矿物特征及成因分析

东秦岭地区发现了两种新型的钼矿床——花岗岩型钼矿床和石英脉状钼矿床。花岗岩型钼矿床矿体赋存于花岗岩中,石英脉型钼矿与石英脉关系密切,矿体分布在石英脉的上下部流纹岩中,前者成矿与燕山期花岗岩热液有关,而后者是否是燕山期花岗岩热液的产物还有待进一步研究。两种类型钼矿床中的辉钼矿与石墨关系密切。     

微晶白云母活性填料的铝酸酯表面改性研究

以微晶白云母为研究对象,铝酸酯DL-411-D为改性剂,研究探讨微晶白云母铝酸酯表面改性工艺务件及其表征方法。经粘度和红外光谱研究证实粘度测试法是确定铝酸酯改性微晶白云母偶联剂用量的有效方法;铝酸酯偶联剂改性微晶白云母工艺简单,偶联剂用量低,不需使用稀释剂,成本低,效果好;改性后的微晶白云母在有机介质中的分散性得到显著提高,因而可大幅度提高其在高聚物中的填充量,降低复合材料的成本。实验结果还表明,铝酸酯改性微晶白云母后,没有发现化学结合的新证据,而更多地显示出物理包覆的特征。     

Comparison of the compositions of crystalline aluminosilicate rocks and their minerals in a planar triangular projection

The problem of comparison of the composition of crystalline rocks with the composition of the constituent minerals of these rocks is considered. It is proposed to present the composition of rocks and the compositions of the constituent minerals in the form of a triangle on the plane. The experience of presentation of compositions in phase diagrams was taken as a basis for the construction. Analysis of the crystallochemical characteristics of clinopyroxenes and garnets has shown that three parameters are enough for depicting the compositions of these and other minerals. For this purpose, similar composition components of rocks and their minerals are summarized in molecular proportions and are plotted on the triangle DO-1/2(R₂O3)-XO₂, where DO = (MgO + CaO + FeO + MnO + NiO + ...) + 1/4(Na₂O + Al₂O₃) + 1/4(K₂O + Al₂O₃), 1/2(R₂O₃) = 1/2(Al₂O₃ + Fe₂O₃ + Cr₂O₃ + ...) - (1/4(Na₂O + Al₂O₃) + 1/4(K₂O + Al₂O₃)), and XO₂ = SiO₂ + TiO₂. The compositions of minerals are expressed as the sums of their components: Ol = Fo + Fa + Lar + Neph + ..., Px = Di + En + Wol + Ged + Gip + Jd + Eg + ..., Ga = Pyr + Gross + Alm + Spe + Ski + Knr + Mj + ..., etc. A step-by-step calculation algorithm is proposed, which permits evaluation of the contents of bi- and trivalent iron during probe microanalyses of garnets and pyroxenes. Comparison of the compositions of deep-seated rocks and their minerals shows their good consistency. The proposed schematic projection permits a visual comparison of the compositions of rocks with low contents of carbonates and water, from ultrabasic (e.g., dunites) to acid (e.g., granites) ones.     

矿床,同步耦合断层和惯量差假说

根据找矿预测中发现的问题,从探索矿床的本质特征入手,重新定义了矿床。根据本文定义的“矿床”及其所规定的矿床学研究要点,又继续探索并发现了板块构造理论中的基本概念———转换断层的本质特征,并将具有此类特征的断层定义为“同步耦合断层”。产生同步耦合断层的地球动力学机制是：非均质的地球作变速自转时,在经向和纬向惯性力同时作用下,惯量不同的相邻板块因惯量差诱发的相对运动。为此,提出了新的地球动力学原理———惯量差假说。根据此假说的基本原理分别构思了地球自转处于减速期、过渡期和加速期的全球构造体系框架。指出同步耦合断层的张性耦合区是控制大型、超大型矿床成带分布的重要空间。以此认识指导找矿预测实践,取得了一定的成效。     

江陵凹陷古新统盐类矿物沉积特征及其成钾指示意义

在对江陵凹陷中GK1、GK2、SK3和B103井岩芯进行详细观察的基础上,借助X射线衍射、扫描电镜、薄片鉴定等手段,确认了在古新统有多种盐类矿物存在,并对盐类矿物特征和矿物组合特征进行了分析。江陵凹陷含盐系地层的矿物种类、组合比较简单,目前发现的盐类矿物有碳酸盐、硫酸盐、氯化物三大类。古新统沙市组沉积时期,出现了大量的盐类矿物,主要为石盐、硬石膏、钙芒硝及无水芒硝,此外,应有少量—微量的钾石盐。作为干热指示矿物的钙芒硝和无水芒硝在沙市组广泛发育,可以推断出江陵凹陷在古新统沙市组时期的古气候属于干热型,此时湖水蒸发作用显著增高,导致古盐湖演化程度较高,向干盐湖阶段发展;而到了新沟嘴组沉积时期,发生湖侵,盐湖水体变深、盐度降低,盐湖遭受淡化。初步判断江陵凹陷古近系沙市组具有较好的成钾条件。     

Metastable staurolite–cordierite assemblage of the Bossòst dome: Late Variscan decompression and polyphase metamorphism in the Axial Zone of the central Pyrenees

A kilometre-scale shear zone is recognized in the Cambro–Ordovician schist of the Bossòst dome, a Variscan metamorphic and structural dome in the Axial Zone of the central Pyrenees. Non-coaxial deformation is recorded by rotated garnet and staurolite porphyroblasts following regional metamorphism M₁, while coaxial conditions prevailed during later contact metamorphic M₂ growth of andalusite and cordierite. Mineral compositions and bulk rock analyses show that garnet–staurolite–andalusite–cordierite assemblages are significantly enriched in Mg and Mn over the garnet–staurolite assemblage, which lacks sufficient Mg for cordierite to form. The garnet–staurolite assemblage preserves conditions during M₁, estimated by AFM diagrams and P–T pseudosections to be 5.5 kbar and 580 °C, respectively. Pseudosections also indicate that staurolite is not a stable phase in cordierite–andalusite assemblages of M₂, suggesting polyphase metamorphism and decompression along a clockwise P–T path for the staurolite–cordierite–andalusite assemblages. This concurs with proposed extensional tectonics along the regional shear zone. To cite this article: J.E. Mezger et al., C. R. Geoscience 336 (2004).