Sustainable Development and Utilization of Mineral Resources:

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Geochemistry of Thermal－Mineral Waters in Siping＇an District， Shanxi Province， China

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Geochronology of the Larderello geothermal field: new data and the “closure temperature” issue

The Larderello geothermal field is generally accepted to have been produced by a granite intrusion at 4–9 km depth. Hydrothermal parageneses and fluid inclusions always formed at temperatures greater than or equal to the current ones, which implies that the field has always undergone a roughly monotonic cooling history (fluctuations < 40 K) since intrusion of the granite at 4 Ma. The heat required to maintain the thermal anomaly over such a long period is supplied by a seismically anomalous body of 32000 km³ rooted in the mantle. Borehole minerals from Larderello are thus a unique well-calibrated natural example of thermally induced Ar and Sr loss under geological conditions and time spans. The observations (biotites retain Ar above 450°C) agree well with other, albeit less precise, geological determinations, but contrast with laboratory determinations of diffusivity from the literature. We therefore performed a hydrothermal experiment on two Larderello biotites and derived a diffusivity D _Lab(370°C)=5.3·10^-18 cm²s^-1, in agreement with published estimates of diffusivity in annite. From D _Lab and the rejuvenation of the K/Ar ages we calculate maximum survival times at the present in-hole temperatures. They trend smoothly over almost two orders of magnitude from 352 ka to 5.3 ka, anticorrelating with depth: laboratory diffusivities are inconsistent not only with geological facts, but also among themselves. From the geologically constrained lifetime of the thermal anomaly we derive a diffusivity D _G(370°C)=3.81·10²¹ cm²s^-1, 3±1 orders of magnitude lower than D _Lab. The cause of these discrepancies must be sought among various laboratory artefacts: overstepping of a critical temperature T ^*; enhanced diffusivities in wet experiments; presence of fast pathway (dislocation and pipe) diffusion, and of dissolution/reprecipitation reactions, which we imaged by scanning electron microscopy. These phenomena are minor in geological settings: in the absence of mineral transformation reactions, complete or near-complete resetting is achieved only by volume diffusion. Therefore, laboratory determinations will necessarily result in apparent diffusivities that are too high compared to those actually effecting the resetting of natural geochronometers.This word is dedicated to the memory of Aldo Valori (1958–1991)     

Nonmetallic Mineral Deposits of China and Plate Tectonics

The Chinese continent is a component part of the present Eurasian plate. The history of its geologicaldevelopment is a process of the convergence of palaeo-plates. the oceanward migration of volcanic belts andvolcanic island-arcs, and the accompanying growth of the intracontinental rifts in the later stage. So theChinese continent abounds in nonmetal resources. Based on the plate-tectonic settings in which those depos-its were formed, the nonmetallic deposits can be generally classified into those related to the sutures andophiolites. those related to the volcanic island-arcs. those related to the back-arc epicontinental sea. those re-lated to the intracontinental rifts and those within the plate interior. They all show certain characteristicregularities of distribution. The evolutionary process of the Chinese continent is so complicated that somenonmetallic deposits have various origins and are characterized by multi-stage mineralization. multiplicityof types and superimposition of mineralization. All these are of great significance in deepening the under-standing of the formation and modes of occurrence of the nonmetallic deposits and in prospecting for min-eral resources.     

Diamonds and Their Mineral Inclusions,and What They Tell Us: A Detailed “Pull-Apart” of a Diamondiferous Eclogite

For the first time, three-dimensional, high-resolution X-ray computed tomography (HRXCT) of an eclogite xenolith from Yakutia has successfully imaged diamonds and their textural relationships with coexisting minerals. Thirty (30) macrodiamonds (≥1 mm), with a total weight of just over 3 carats, for an ore grade of some 27,000 ct/ton, were found in a small (4 × 5 × 6 cm) eclogite, U51/3, from Udachnaya. Based upon 3-D imaging, the diamonds appear to be associated with zones of secondary alteration of clinopyroxene (Cpx) in the xenolith. The presence of diamonds with secondary minerals strongly suggests that the diamonds formed after the eclogite, in conjunction with meta-somatic input(s) of carbon-rich fluids. Metasomatic processes are also indicated by the non-systematic variations in Cpx inclusion chemistry in the several diamonds. The inclusions in the diamonds vary considerably in major- and trace-element chemistry within and between diamonds, and do not correspond to the minerals of the host eclogite, whose compositions are extremely homogeneous. Some Cpx inclusions possess +Eu anomalies, probably inherited from their crustal source rocks. The only consistent feature for the Cpx crystals in the inclusions is that they have higher K₂O than the Cpx grains in the host.

The δ¹³C compositions are relatively constant at ?5% both within and between diamonds, whereas δ¹⁵N values vary from ?2.8% to ?15.8%. Within a diamond, the total N varies considerably from 15 to 285 ppm in one diamond to 103 to 1250 ppm in another. Cathodoluminescent imaging reveals extremely contorted zonations and complex growth histories in the diamonds, indicating large variations in growth environments for each diamond.

This study directly bears on the concept of diamond inclusions as time capsules for investigating the mantle of the Earth. If diamonds and their inclusions can vary so much within this one small xenolith, the significance of their compositions is a serious question that must be addressed in all diamond-inclusion endeavors.     

Development and Utilization of the World’s and China’s Bulk Mineral Resources and their Supply and Demand Situation in the Next Twenty Years

Bulk mineral resources of iron ores, copper ores, bauxite, lead ores, zinc ores and potassium salt play a pivotal role on the world’s and China’s economic development. This study analyzed and predicted their resources base and potential, development and utilization and their world’s and China’s supply and demand situation in the future 20 years. The supply and demand of these six bulk mineral products are generally balanced, with a slight surplus, which will guarantee the stability of the international mineral commodity market supply. The six mineral resources(especially iron ores and copper ores) are abundant and have a great potential, and their development and utilization scale will gradually increase. Till the end of 2014, the reserveproduction ratio of iron, copper, bauxite, lead, zinc ores and potassium salt was 95 years, 42 years, 100 years, 17 years, 37 years and 170 years, respectively. Except lead ores, the other five types all have reserve-production ratio exceeding 20 years, indicative of a high resources guarantee degree. If the utilization of recycled metals is counted in, the supply of the world’s six mineral products will exceed the demand in the future twenty years. In 2015–2035, the supply of iron ores, refined copper, primary aluminum, refined lead, zinc and potassium salt will exceed their demand by 0.4–0.7 billion tons(Gt), 5.0–6.0 million tons(Mt), 1.1–8.9 Mt, 1.0–2.0 Mt, 1.2–2.0 Mt and 4.8–5.6 Mt, respectively. It is predicted that there is no problem with the supply side of bulk mineral products such as iron ores, but local or structural shortage may occur because of geopolitics, monopoly control, resources nationalism and trade friction. Affected by China’s compressed industrialized development model, the demand of iron ores(crude steel), potassium salt, refined lead, refined copper, bauxite(primary aluminum) and zinc will gradually reach their peak in advance. The demand peak of iron ores(crude steel) will reach around 2015, 2016 for potassium salt, 2020 for refined lead, 2021 for bauxite(primary aluminum), 2022 for refined copper and 2023 for zinc. China’s demand for iron ores(crude steel), bauxite(primary aluminum) and zinc in the future 20 years will decline among the world’s demand, while that for refined copper, refined lead and potassium salt will slightly increase. The demand for bulk mineral products still remains high. In 2015–2035, China’s accumulative demand for iron ores(crude steel) will be 20.313 Gt(13.429 Gt), 0.304 Gt for refined copper, 2.466 Gt(0.616 Gt) of bauxite(primary aluminum), 0.102 Gt of refined lead, 0.138 Gt of zinc and 0.157 Gt of potassium salt, and they account for the world’s YOY(YOY) accumulative demand of 35.17%, 51.09%, 48.47%, 46.62%, 43.95% and 21.84%, respectively. This proportion is 49.40%, 102.52%, 87.44%, 105.65%, 93.62% and 106.49% of that in 2014, respectively. From the supply side of China’s bulk mineral resources, it is forecasted that the accumulative supply of primary(mine) mineral products in 2015–2035 is 4.046 Gt of iron ores, 0.591 Gt of copper,1.129 Gt of bauxite, 63.661 Mt of(mine) lead, 0.109 Gt of(mine) zinc and 0.128 Gt of potassium salt, which accounts for 8.82%, 13.92%, 26.67%, 47.09%, 33.04% and 15.56% of the world’s predicted YOY production, respectively. With the rapid increase in the smelting capacity of iron and steel and alumina, the rate of capacity utilization for crude steel, refined copper, alumina, primary aluminum and refined lead in 2014 was 72.13%, 83.63%, 74.45%, 70.76% and 72.22%, respectively. During 2000–2014, the rate of capacity utilization for China’s crude steel and refined copper showed a generally fluctuating decrease, which leads to an insufficient supply of primary mineral products. It is forecasted that the supply insufficiency of iron ores in 2015–2035 is 17.44 Gt, 0.245 Gt of copper in copper concentrates, 1.337 Gt of bauxite, 38.44 Mt of lead in lead concentrates and 29.19 Mt of zinc in zinc concentrates. China has gradually raised the utilization of recycled metals, which has mitigated the insufficient supply of primary metal products to some extent. It is forecasted that in 2015–2035 the accumulative utilization amount of steel scrap(iron ores) is 3.27 Gt(5.08 Gt), 70.312 Mt of recycled copper, 0.2 Gt of recycled aluminum, 48 Mt of recycled lead and 7.7 Mt of recycled zinc. The analysis on the supply and demand situation of China’s bulk mineral resources in 2015–2035 suggests that the supply-demand contradiction for these six types of mineral products will decrease, indicative of a generally declining external dependency. If the use of recycled metal amount is counted in, the external dependency of China’s iron, copper, bauxite, lead, zinc and potassium salt will be 79%, 65%, 26%, 8%, 16% and 18% in 2014, respectively. It is predicted that this external dependency will decrease to 62%, 64%, 20%,-0.93%, 16% and 14% in 2020, respectively, showing an overall decreasing trend. We propose the following suggestions correspondingly.(1) The demand peak of China’s crude steel and potassium salt will reach during 2015–2023 in succession. Mining transformation should be planned and deployed in advance to deal with the arrival of this demand peak.(2) The supply-demand contradiction of China’s bulk mineral resources will mitigate in the future 20 years, and the external dependency will decrease accordingly. It is suggested to adjust the mineral resources management policies according to different minerals and regions, and regulate the exploration and development activities.(3) China should further establish and improve the forced mechanism of resolving the smelting overcapacity of steel, refined copper, primary aluminum, lead and zinc to really achieve the goal of "reducing excess production capacity".(4) In accordance with the national strategic deployment of "One Belt One Road", China should encourage the excess capacity of steel, copper, alumina and primary aluminum enterprises to transfer to those countries or areas with abundant resources, high energy matching degree and relatively excellent infrastructure. Based on the national conditions, mining condition and geopolitics of the resources countries, we will gradually build steel, copper, aluminum and lead-zinc smelting bases, and potash processing and production bases, which will promote the excess capacity to transfer to the overseas orderly.(5) It is proposed to strengthen the planning and management of renewable resources recycling and to construct industrial base of renewable metal recycling.(6) China should promote the comprehensive development and utilization of paragenetic and associated mineral species to further improve the comprehensive utilization of bulk mineral resources.     

Primary Mineral Information and Depositional Models of Relevant Mineral Facies of the Early Precambrian BIF—A Preliminary Review

The primary mineral compositions of BIF are regarded as ferric oxyhydroxide or iron silicate nanoparticles (mainly greenalite and stilpnomelane ) whichcan transform into minerals like hematite, magnetite and siderite. On the basis of predominant iron minerals, three distinctive sedimentary facies are recognized in BIF: oxide facies, silicate facies and carbonate facies. Marked by the Great Oxidation Event (GOE, 2.4~2.2 Ga), sedimentary facies can be divided into two models: “anoxic and reducing” model and “stratified ocean” model. The ancient ocean was anoxic and reducing before GOE, and under this circumstance, BIF was distributed from the distal to proximal zones transforming from hematite facies through magnetite facies to carbonate facies, such as West Rand Group BIF (2.96~2.78 Ga) and Kuruman BIF (~2.46 Ga) in south Africa. However, the ancient ocean was a stratified ocean during and after GOE, which means that shallow seawater was oxidizing while deeper seawater was reducing, leading to an opposite sedimentary facies distribution compared to the former one: BIF was distributed from the distal to proximal zones transforming from carbonate facies through magnetite facies to hematite facies, such as Yuanjiacun BIF in China (~2.3 Ga) and Sokoman iron formation in Canada (~1.88 Ga). Overall, BIF is an unrepeatable formation in geological history, which can only form in specific sedimentary environment. The key point to speculate the paleo-ocean environment, namely the problems to be solved at the moment, is to identify and derive the primary mineral compositions, to make sure the genetic mechanism of sedimentary facies especially silicate facies, to restrict the sedimentary conditions and to study microbial activities contacting with BIF.     

Mineral and thermal waters of the Ipelská Pahorkatina hillyland

 Mineral and thermal waters occur at Kalinciakovo, Santovka, Dudince, Slatina and Turovce, in the inner side of the Western Carpathian arc, the south-western margin of the Central Slovak Neovolcanics, and on the so-called Levice spring line. They are important sources of mineral waters for Slovakia, which are used for different purposes (bathing therapy, bottling, recreation). The mineral and thermal waters of Dudince have an extraordinary position among them. The mineral water with its physico-chemical composition and content of gasses enables its wide use for bathing therapy and it occupies a special position among the mineral waters of the Carpathian arc. Received: 9 November 1998 · Accepted: 2 March 1999     

Editorial to “Heat Flow: Recent Advances”

International Journal of Earth Sciences -     

Preparation of Cristobalite and It’s Thermal Characteristics

The thermal characteristic of cristobalite plays an important role in the application of casting industry. Because the phase transition of silica glass and cristobalite has low volume change, the block cristobalite had been manufactured by calcining fused silica ceramic, the XRD, SEM and thermal characteristics of the cristobalite had been tested. The result shows the formation of porous structure in the block cristobalite, and thermal expansion rate of the phase transition of β/αcristobalite reaches 1.5% at the temperature range of 250-290 ℃.     

Theory and Method of Mineral Resource Prediction Based on Synthetic Information

Metallogenic prognosis of synthetic information uses the geological body and the miaeral resource body as a statistical unit to interpret synthetically the information of geology, geophysics, geo-chemistry and remote sensing from the evolution of geology and puts all the information into one entire system by drawing up digitalized interpretation maps of the synthetic information. On such basis, differ-ent grades and types of mineral resource prospecting models and predictive models of synthetic informa-tion can be established. Hence, a new integrated prediction system will be formed of metallogenic prog-nosis (qualitative prediction), mineral resources statistic prediction (determining targets) and mlaeral resources prediction (determining resources amount).     

Structural Evolvement of Heating Treatment of Mg/AI-LDH and Preparation of Mineral Mesoporous Materials

Although hydrotalcite, or layered double hydroxides （LDHs）, is not a common mineral, it is an important material that can be easily synthesized in laboratory. In this study, structural evolvement and BET surface area changes of heat treated Mg/AI-LDH is evaluated by XRD, TEM and N2-BET analyses. The results indicate that the magnesium-aluminum LDH with carbonate as interlayer anion, periclase-like oxides was formed at temperatures of 400-800℃. Meanwhile, 2-3 nanometer mesoporous were formed during decomposition of LDH. However, the heat treated samples still preserve the morphology of the original LDH plates. Periclase-like formed from LDH heat treatment may re-hydrolyze and recover the structure of LDH. However, crystallinity of the recovered LDH is lower than that of the original LDH. This heat treatment will result in formation of （Mg, Al）-oxide nano-crystals and nanopores among the nano-crystals. When heating temperature exceeds 1000, the periclase-like （Mg, Al）-oxide is transformed into a composite with periclase （MgO） and spinel phases. The periclase can be re-hydrolyzed and dissolved in HCl solution. After acid treatment, the sample with a high surface area is composed of spinel nano-crystals and nanopores among them. Our results will provide a new and economic way to synthesize mesoporous materials through pathways of phase transformation of precursor materials with different composition.