Hasil untuk "Mineralogy"

Saeed Kamran, Ahmad Ahamadi Khalaji, Mehdi Rezaei-Kahkhaei et al.

IntroductionVolcanic rocks widely extended throughout the Earth's continental crust (Brilhante et al., 2024). Among the different tectonic setting, a group of igneous rocks is related to volcanic arc; these rocks, according to Tang et al. (2022), include a range of mafic-intermediate rocks with SiO2 (47.34-60 wt%), Fe2O3 (11.63-73.4 wt%) and Mg coefficient (26-66 wt%), remarkable chemical criteria are related to calc-alkaline series with medium to high potassium and LILE enrichment. Moreover, the Ce negative anomaly in these rocks is consistent with the subduction zone. In this paper, based on whole-rock chemistry data, the geochemical properties of volcanic rocks of the Ahovan area in northeast of Semnan (Central Iran) are investigated. The main purpose of the present paper is the study of tectonic setting as well as the tectonomagmatism of these rocks.Analytical MethodsDuring the field studies, 80 samples were collected from the volcanic rocks for petrographic observations. Following the preparation of thin sections, their mineralogy and textural relationships were carefully considered, and 10 of them with least alteration were sent to the ALS-CHEMEX laboratory in Canada for identification of major elements by ICP-OES and trace and rare earth elements by ICP-MS (Table 1). Furthermore, 11 samples of the Khalatbari-Jafari and Etesami (2018) were used in this study for comparison The measurement accuracy for all major elements was 0.01%w.t, the maximum measurement accuracy in the trace elements for Cr, Li, and Tl was 10 ppm and for Cs, Ho, Lu, Tb, and Tm was 0.01 ppm.Petrography According to field studies, the Eocene volcanic units, trending east-west, are much more widespread than the intrusive rocks of Ahovan area. These units have a mixed spectrum of basalt, trachyte and andesite-trachyandesite, which the latter rocks cover a large volume.The basaltic rocks, with gray and black in color, are dominated by the presence of plagioclase and clinopyroxene as the main minerals. The white and grayish white andesite-trachyandesite are characterized by the occurrence of plagioclase, clinopyroxene, amphibole and biotite as well as porphyry and microlithic porphyry textures. Trachyte rocks are white and grayish white in hand spacemen. Plagioclase and sanidine as phenocrysts and microlites constitute the main minerals of the trachyte rocks. Amphibole and biotite are small amounts in these rocks (10 vol.%). Iron oxides, calcite, chlorite and epidote are the alteration products of these minerals. Dolerite dykes, trending N-S and a maximum thickness of 2 m crosscut all the volcanic rocks. under study.GeochemistryThe overall petrographic and geochemical data point to the nature of calc-alkaline to high-potassium calc-alkaline of the rocks studied, which are originated by the low-pressure melting of spinel lherzolite and developed at a depth less than the garnet stability field. In the Y versus Zr diagram, the study rocks are in the volcanic arc setting. The REE pattern of the study rocks normalized to chondrite follow the sloping pattern of calc-alkane rocks related to island arcs. In spider diagram of incompatible elements normalized to N-MORBs, the study rocks show LILE enrichment and HFSE depletion indicating the crustal contamination process involved in the formation of these rocks. The depletion of Nb, Ti and Ta show characteristics of arc islands. Moreover, LILE's enrichment such as K and Sr indicate that the rocks under study originated from the mantle metasomatism resulting from hydrous fluids penetrated from the subducting crust into the mantle wedge at different depths.ConclusionThe volcanic rocks of Ahovan area are dominated by the presence of basalt, andesite-trachyandesite and trachyte belonging to Middle-Late Eocene. A series of trachybasalt and basalt-trachyandesite dykes, trending north-south, and a maximum thickness of 2 meters, crosscut the rocks of the area. The essential minerals of basalts are plagioclase and clinopyroxene and those of andesite-trachyandesite are plagioclase, clinopyroxene, amphibole and biotite. Plagioclase and sanidine are the dominant minerals of trachytes. In magmatic series diagram, all the rocks studied are in the range of calc-alkaline to high-potassium calc-alkaline series, originated from a relatively low-pressure melting of spinel lherzolite at a depth of lower than the garnet melting stability field. The Chondrite-normalized rare earth element (REE) patterns are similar to calc-alkaline rocks from island arc. Also, in the spider diagram of incompatible elements normalized to N-MORB, these rocks show enrichment in LILE and depletion in HFSE indicating the involvement of the crustal contamination process in formation of these rocks. The LILE enrichment (i.e., K and Sr) points to mantle alteration resulting from aqueous fluids penetrated from the subducting crust of the Neotethys ocean into the mantle wedge at different depths played a role in the formation of these rocks. In tectonic setting diagrams, the rocks under investigation are in the range of calc-alkaline basalts related to volcanic arcs.

S. Raut, N. Andure, A. Kadam et al.

This research investigates the application of hyperspectral imaging (HSI) for surface clay and mineral exploration, specifically targeting kaolin, hematite, saponite, and illite in the Udaipur region of Rajasthan, India an area known for its complex and diverse mineralogy. Traditional approaches such as geological mapping, geochemical assays, and field surveys, while fundamental, often prove inefficient in terms of time and resources, especially in the challenging topography of the Aravalli Range. HSI, leveraging data from the Hyperion sensor, offers a fine-resolution remote sensing method capable of discriminating minerals through their unique spectral reflectance profiles. The study employs advanced HSI processing techniques, including Minimum Noise Fraction (MNF) transformation for noise reduction and feature space optimization, and Pixel Purity Index (PPI) for endmember extraction, followed by mineral classification using Spectral Angle Mapper (SAM). A detailed pre-processing workflow is implemented, involving atmospheric correction, radiometric calibration, and the generation of endmember spectra based on USGS mineral spectra of key minerals. SAM is used to classify mineralogical components by computing the spectral angle between the pixel spectra and the known spectral profiles. Results demonstrate that this integrated approach—combining HSI with MNF, PPI, and SAM algorithms significantly enhances the accuracy and precision of clay and mineral detection, specifically identifying clay kaolinite, illite, saponite, and hematite, along with their spatial distribution within the study area. This methodology offers a scalable, cost-effective, and highly reliable solution for mineral exploration, particularly for identifying surface clay minerals and other mineral resources in geologically complex regions such as Udaipur. The study's findings not only enhance the understanding of mineral resources in the Udaipur region but also highlight the potential of HSI in climate change research. By providing precise data on mineral distribution and soil composition, HSI can be a valuable tool for creating adaptive land-use strategies, supporting sustainable agriculture, and mitigating the impacts of climate change, ultimately contributing to more resilient ecosystems and informed decision-making in geospatial research and sustainable development.

Carlos Neto de Carvalho, Pedro Proença Cunha, João Belo et al.

Abstract Multiple sources of evidence for the systematic use of coastal ecosystems and resources by Neanderthals are known. Fossil hominin footprints offer direct portraits of individual or social group presence and locomotor behavior, and interspecific interactions, in the coastal ecospace. Here we describe the first two hominin tracksites found in the southwestern most region of Europe. At Monte Clérigo, dated to 78 ± 5 ka, trackways of three individuals demonstrate how Neanderthals navigated dune landscapes. These behaviors suggest route planning, with dune systems serving as advantageous settings for ambush hunting or stalking prey. A single footprint at Praia do Telheiro site, dated to 82 ± 5 ka, sustains the presence of Neanderthals in the dune ecosystem during Marine Isotope Stage (MIS) 5a. Network analysis provided dietary preferences and ecological interactions of Neanderthals in coastal areas. A review of the Neanderthal coastal sites associated with faunal evidence shows that their diet was primarily centered on cervids, horses and hares. The consistent presence of these mammal taxa highlights their role as reliable food sources, irrespective of the varying environments inhabited by Neanderthals. In addition, the Neanderthal diet also incorporated animals from neighboring littoral habitats, indicating a broad foraging strategy that capitalized on local biodiversity.

Ibrahim A. Salem, Samir M. Aly, Ali Shebl et al.

Abstract A comprehensive, multiscale investigation, integrating remote sensing, mineralogy, whole rock chemistry, Electron Microprobe (EMP), and stable isotopes (oxygen-18O and carbon-13C), was undertaken to assess the feasibility of talc deposits and their host serpentinite at Gebel El-Maiyit in the Eastern Desert of Egypt. Sentinel 2 remote sensing images were applied to discriminate talc from serpentinites followed by geochemical study of serpentinites using RO`/SiO2 ratios, AFM diagram and MgO versus SiO2 relationship indicates a peridotite origin formed at low temperature Alpine type. Our study revealed that talc deposit has a varied mineralogical composition and according to the predominant talc and gangue minerals three main types have been distinguished: 1- pure talc, 2- tremolite talc and 3- chlorite talc. Paragenetically, talc is derived from serpentine minerals, tremolite and chlorite. The latter is formed at about 231 °C. The chemical data of talc deposit reveals that the summation of talc components (SiO2 + MgO + H2O) is 92.68%, while that of impurity oxides (Al2O3 + CaO + Fe2O3 + FeO) is 5.56%. The carbon13C) and oxygen18O) contents of pure magnesite revealed that the pure phase of Gebel El-Maiyit was formed at low temperature (around 100 °C) while magnesite contained in talc carbonate rock was formed at high temperature (140–175 °C). In terms of source fluids, the metamorphic and /or magmatic water was supposed to be the main fluids which are circulated during the hydrothermal alteration. Although S and P are very minor components in all the talc ore types of the considered area and do not affect their industrial use. Copper (Cu) was not detected. Iron (Fe) and manganese (Mn) concentrations are significantly high, necessitating treatment to reduce these elements for the ore to be suitable as an electrical insulator. Arsenic (As) levels are consistently below 5 ppm, indicating the ore’s potential use in the cosmetic industry without further processing.

Jane H. Scarrow, Matthew J. Pankhurst, Olivia A. Barbee et al.

We present an integrated petrological study of the 2021 Tajogaite eruption, La Palma, examining magmatic processes that initiated, sustained, and terminated surface volcanic activity. High temporal resolution sampling of near-continuously erupted alkali-basalt lava and tephra over the 85-day event reveals magma plumbing system dynamics from compositional trends. Initial deposits were mineralogically varied, reflecting mobilisation of shallow, evolved mush perturbed by fresh deep, primitive magma influx (Stage 1 - initiation). Transition to more primitive, uniform compositions recorded progressively deeper tapping of pre-existing magmatic zonation (Stage 2 - evacuation). The final stage (Stage 3 - waning) was characterised by more evolved magma compositions on the same fractionation trend as Stage 2, with tephra glass compositions suggesting a proportionately larger role of mush interstitial melts. We suggest this reflects shutdown of mantle-derived magma supply, a key process in eruption waning and termination, and compression-driven melt extraction of less mobile melts. Correlation with geophysical monitoring data demonstrates how near-real-time petrological monitoring could improve understanding of when an eruption may end.

Xiao Wu, Jianxi Zhu, Hongping He et al.

Abstract One of the paradoxes of the Archean rock record is how evidence for oxidative continental weathering is plausible when the atmosphere lacked oxygen prior to the Great Oxidation Event ca. 2.5 billion years ago. We detected reactive oxygen species (ROS) production at various silicate-water interfaces in a simulated Archean atmosphere and calculated homolysis rates of silicon–oxygen bonds in these minerals. We find that ROS can be produced while silicates were eroded and transported by streams to depositional basins. The magnitude of ROS production increases from mafic- to felsic-silicates. During early continent formation, e.g., the Kaapvaal and Pilbara basins in the Paleoarchean, the emplacement of granitoids and their subsequent exposure to physical weathering might have annually provided at least 1.73 × 108 mol O2 before the biological O2 production. Importantly, this process could have oxidatively mobilized redox-sensitive elements to seawater, increasing the availability of bioessential nutrient elements for the Archean biosphere.

Petrov V., Minaev V., Ustinov S. et al.

The article deals with the creation of an information and analytical platform for assessing external causes of technogenic (man-made) accidents and for improving methods of their predication and prevention on the territories of long-term geological, mining, and engineering activities on the Southeastern (SE) Transbaikal region example – one of the key areas for mining and extraction of the strategic raw minerals in Russia. 3D modeling of active geological structures and hazardous seismogeodynamic processes on GIS-based technologies is a key instrument for forecasting dangerous natural and technogenic events and risk reduction of their occurrence. A matter of minimizing consequences of natural and technogenic disasters for such facilities of increased technological and environmental hazards as minefields, radiochemical facilities, sites for spent nuclear material disposal, dams, gas and oil pipelines, etc. has become essential. It is necessary to assess modern geodynamic territory’s activity on a unified geoinformation platform applying the newest integrated geological-geophysical researches’ methods for these objects, to select seismically active fault-fracture zones, to determine the rate and direction of surface displacement, to establish patterns of subsoil stressed-strained state natural component influence on behavior of local technogenic processes. Taking into account the specificities of geotectonic structure of mining territories, the structure of monitoring seismogeodynamic processes network on multifunctional geodynamic test sites should be developed. Observations made on test sites form the information basis for forecasting of lithosphere condition, taking decisions on rational subsurface management and providing ecological safety of the territory.

Juan Carlos Fernández-Caliani, Inmaculada Giráldez, Sandra Fernández-Landero et al.

A field-based experiment was set up to evaluate the effectiveness of a single application of marble waste sludge (MWS) on chemical immobilization of potentially hazardous trace elements (PHE) within the soil profile of a mine Technosol under natural assisted remediation for 12 years. Results showed that MWS amendment significantly reduced soil acidity and PHE mobility compared to unamended soil, thus improving soil health and plant growth. The amendment application had a sustained acid-neutralizing action, as soil pH remains relatively constant at between 5.8 and 6.4 throughout the entire profile (70 cm depth). In addition to diluting pollutants, the treatment triggered a redistribution of trace elements among the various operationally defined geochemical pools, shifting the PHE speciation from water-soluble forms to fractions associated with carbonates (29% Cd), metal oxides (40–48% Zn, Cd, Cu, and Ni), organic matter (22% Cu and Ni), and insoluble secondary oxidation minerals and residual phases (80–99% As, Cr, Sb, Tl, and Pb), thereby effectively limiting its potential environmental significance. MWS treatment to immobilize PHE in the contaminated mine Technosol was effective and persistent while in the untreated soil metal release is continuing over time.

جواد غلام نژاد, رضا لطفیان, یوسف میرزائیان لرد کیوان

<span lang="AR-SA" dir="RTL">با توجه به نقش بازیابی در محاسبه ارزش اقتصادی بلوک کانسنگ و تأثیر مقدار این ارزش بر محاسبات طراحی و برنامه</span><span>‌</span><span lang="AR-SA" dir="RTL">ریزی تولید معدن، تعیین بازیابی فلز از بلوک کانسنگ ارسالی به کارخانه فرآوری، از اهمیت بالایی برخوردار است. هدف از این پژوهش، بررسی قابلیت برآورد بازیابی بلوک کانسنگ به</span><span>‌</span><span lang="AR-SA" dir="RTL">صورت کیفی و با روش‌های مبتنی بر طبقه‌بندی داده‌ها از مجموعه روش‌‌های داده‌کاوی و به</span><span>‌</span><span lang="AR-SA" dir="RTL">صورت کمّی، با دو روش رگرسیون چندمتغیره و مدل هوشمند شبکه عصبی، بر اساس داده</span><span>‌</span><span lang="AR-SA" dir="RTL">های آنالیز خوراک ورودی کارخانه است. برای نیل به این هدف، معدن مس میدوک مورد مطالعه قرار گرفت و با استفاده از 58 نمونه آنالیزشده عیار خوراک کارخانه،  شامل عیارهای </span><span>Cu</span><span lang="AR-SA" dir="RTL">، </span><span>CuO</span><span lang="AR-SA" dir="RTL">و </span><span>CuS</span><span dir="RTL"> <span lang="AR-SA">و میزان بازیابی عنصر </span></span><span>Cu</span><span dir="RTL"> <span lang="AR-SA">در محصول نهایی، فرآیند پیش‌بینی بازیابی کل ذخیره به</span></span><span>‌</span><span lang="AR-SA" dir="RTL">صورت کیفی با روش‌های طبقه‌بندی درخت تصمیم، قانون بیز و  الگوریتم نزدیک</span><span>‌</span><span lang="AR-SA" dir="RTL">ترین همسایه انجام شد. برای برآورد کمّی میزان بازیابی ذخیره، مدل رگرسیون چندمتغیره و شبکه عصبی مصنوعی برای شاخص‌های عیاری مذکور و میزان بازیابی بین 47 نمونه از 58 نمونه برقرار شد و توسط 11 نمونه آنالیزشده آزمایشی، مدل</span><span>‌</span><span lang="AR-SA" dir="RTL">های به</span><span>‌</span><span lang="AR-SA" dir="RTL">دست</span><span>‌</span><span lang="AR-SA" dir="RTL">آمده اعتبارسنجی شدند. معیارهای میانگین خطا و جذر میانگین مربعات خطا در مدل رگرسیونی به ترتیب 021702_/0 و 024972_/0 و در مدل شبکه عصبی مصنوعی به ترتیب 015753_/0 و 021404_/0 محاسبه شدند. بنابراین مدل شبکه عصبی مصنوعی به</span><span>‌</span><span lang="AR-SA" dir="RTL">عنوان ابزار دقیق</span><span>‌</span><span lang="AR-SA" dir="RTL">تری در پیش</span><span>‌</span><span lang="AR-SA" dir="RTL">بینی بازیابی نسبت به مدل رگرسیون چندمتغیره عمل می</span><span>‌</span><span lang="AR-SA" dir="RTL">کند. نتایج آنالیز حساسیت این مدل نشان داد، عیار </span><span>Cu</span><span dir="RTL"> <span lang="AR-SA">مهم</span></span><span>‌</span><span lang="AR-SA" dir="RTL">ترین عامل و عیار </span><span>CuO</span><span dir="RTL"> <span lang="AR-SA">و </span></span><span>CuS</span><span dir="RTL"> <span lang="AR-SA">نیز به ترتیب، دیگر عوامل تاثیرگذار بر تغییرات بازیابی هستند.</span></span>

D. E. Tonkacheev, D. A. Chareev, V. D. Abramova et al.

Research subject. Sphalerite (ZnS) is a widespread mineral that can be found in various depositional environments. During formation, this mineral can accumulate minor and trace impurities, with gold being one of the most valuable component. The issue of the chemical state of Au in sphalerite has been much discussed recently.Methods. Samples of In-, Fe- and In-Febearing sphalerite with a composition ranging from 0 to 2.5 mol.% In2S3 and 0 – 40 mol.% FeS were synthesized in an Ausaturated system using gas transport and salt flux techniques. The resulting products were subsequently investigated using EPMA and LA-ICP-MS. Results. All the elements under investigation are found to be homogeneously distributed within the sphalerite matrix. After quenching, sphalerite is shown to retain Au. Our data indicates that the observed increase in Au concentration is caused by the presence of In (up to 1.02 wt % Au) and, to a lesser extent, by that of Fe (up to ≈600 ppm Au). These elements substitute Zn in the crystal structure of sphalerite following the scheme Au+ + In3+(Fe3+) ↔ 2Zn2+, which is in good agreement with previous data obtained using the XAS method.Conclusions.A higher sulphur fugacity in the system leads to a more significant accumulation of Au in sphalerite. The concentration of Au in pure sphalerite does not exceed 10 ppm under our experimental conditions and does not depend on the activity of sulphur in the system.

Maria A. Pereira de Barros da Silva, Héctor M. Fernández-Núñez, João Júnior-Baptista et al.

The use of the surface wave’s analysis in its passive and active variants was jointly assessed by the shallow seismic refraction. It allows determining dynamic parameters from the longitudinal and transverse velocities, obtained from seismic methods. For the first time, based on the performance of seismic wave velocities, the soils of Luanda city in Angola are characterized and it is demonstrated that a group of seismic methods formed with the multichannel analysis of surface waves and the shallow seismic refraction in its variant 2D MASW, allows greater continuity in the geotechnical characterization of soils.

Roghieh Doroozi, Carmela Vaccaro, Fariborz Masoudi et al.

The Triassic alkaline basaltic rocks (TABR) of North Kamarbon are located in Central Alborz, which is regarded as the northern part of the Alpine-Himalayan orogenic belt. Fractional crystallization does not appear as a major process in the genesis of TABR while different degree of partial melting may be regarded as the main process, based on petrography and geochemistry studies. The geochemical characteristics of TABR are in conflict with a substantial involvement of continental crust or crustal contamination. High (La/Yb)N and (Dy/Yb)N ratios, along with other geochemical features, in the TABR magma, suggest an asthenospheric origin, with low degree of partial melting of a garnet-bearing mantle sources. Enrichment patterns of LILE (Ba, Sr and Th), HFSE (Nb, Ta and Zr) and P, and depletion at HREE (Yb, Lu) are similar to what observed for OIB or intraplate alkaline magmatic rocks. The Sr and Nd isotopic ratios range from 0.70448 to 0.70522 and from 0.51269 to 0.51280, respectively, suggesting time-integrated slightly depleted magma sources. The data indicate that the evolution of TABR could be related to the rifting basin, in Late Triassic, which caused their development by upwelling and decompressional melting of an asthenospheric mantle, without a major involvement of subcontinental lithospheric mantle or crustal contamination. Keywords: Mantle source, Rifting basin, Central Alborz, Iran

István Gómez-Ríos, Lorenzo Perdomo-González, Amado Cruz-Crespo et al.

Obtaining metal alloys of iron and slag from the Aluminothermic processing of industrial solid waste is the purpose of this study. Seven mixtures were obtained by using a Mc Lean Anderson experimental design, where the amount of aluminum varied from 33 to 45 g, the ash 0 to 20 g, the graphite from 0 to 4 g, keeping the lamination scale in 100 g. The performance of the process in terms of quantity and efficiency of metal and slag was evaluated; As a result, the three best alloy mixtures were selected whose carbon content was between 1.33 - 3.62%, silicon of 0.24 - 0.96%, manganese between 0.41 - 0.78% of aluminum and between 0.2 - 11%, and a group of high-value alloy elements (Mn, Cr, Mo, Ni, V, Ti, Nb, Co and W). The technical feasibility of the aluminothermic processing of this industrial waste allows recovering its metallic components, which guarantees the use of these alloys in the industry, while reducing the levels of environmental contamination.

Alexander Birich, Bernd Friedrich, Lars Gronen et al.

Very often, the production of silver causes devastating environmental issues, because of the use of toxic reagents like cyanide and mercury. Due to severe environmental damage caused by humans in the last decades, the social awareness regarding the sustainable production processes is on the rise. Terms like “sustainable” and “green” in product descriptions are becoming more and more popular and producers are forced to satisfy the rising environmental awareness of their customers. Within this work, an alternative environmental sound silver recovery process was developed for a vein type silver ore from Mina Porka, Bolivia. A foregoing characterization of the input material reveals its mineral composition. In the following mineral processing, around 92.9% silver was concentrated by separating 59.5 wt. % of non-silver minerals. Nitric acid leaching of the generated concentrate enabled a silver recovery of up to 98%. The dissolved silver was then separated via copper cementation to generate a metallic silver product of &gt;99% purity. Summarizing all process steps, a silver yield of 87% was achieved in lab scale. A final upscaling trial was conducted to prove the process’ robustness. Within this trial, almost 4 kg of metallic silver with a purity of higher than 99.5 wt. % was produced.

Uğur AKIN

Bu araştırmada, görünür yoğunluk süzgeci kullanılarak Türkiye için gravite görünür yoğunluk verileri hesaplanmış ve bu veri kümesinden sismik hız dağılım haritası elde edilmiştir. Hesap edilen bu iki veri kümesi yorumlanarak Conrad süreksizliğinin üç-boyutlu yapısı ortaya konmuştur. Görünür yoğunluk süzgeci gravite verilerinden farklı derinlik seviyeleri için görünür yoğunluk hesaplanmasında kullanılan bir süzgeçtir. Bu çalışmada, daha önceden hesaplanan Anadolu’nun kıtasal kabuk kalınlığı dağılımı göz önünde bulundurularak, farklı derinlik seviyeleri için yoğunluk haritaları oluşturulmuş ve bu haritalar yorumlanmıştır. Türkiye’nin farklı seviyelerinde en düşük yoğunluk 2.23 gr/cm³, en yüksek yoğunluk 3 gr/cm³ iken ortalama yoğunluk değeri 2.698 gr/cm³ olarak hesaplanmıştır. Farklı kalınlıklar için sismik hız en düşük 3.20 km/sn, en yüksek 6.83 km/sn ve Türkiye’nin Moho (Mohorovičić) süreksizliğine kadar 10 km artan derinlikler için sismik hız ortalaması 5.66 km/sn olarak hesap edilmiştir. Kıtasal kabuğun ilk 20 km’sinde yoğunluk 2.74 gr/cm³ ve sismik hız 5.86 km/sn ile en yüksek değerlerini almıştır. Bu zon aynı zamanda alt kabuk ile üst kabuk arasındaki Conrad süreksizliği olup, Türkiye’deki ortalama derinliği 16 km’dir. SİAL-SİMA arasında gelişen Conrad süreksizlik sınırının Doğu Anadolu Yüksek Platosu’nda görülememiş olması, SİMA’nın jeolojik evrim neticesinde yok olduğunu, mevcut kabuğun ise sadece SİAL kökenli olabileceğini düşündürmüştür.

Kelvin Anderson, F. Wall, G. Rollinson et al.

R. Alonso-Santurde, A. Coz, J. Viguri et al.

Alfredo L. Coello-Velázquez

Con el propósito de disminuir los errores (residuos) que tienen lugar en la determinación de la carga circulante en los circuitos cerrados de molienda o trituración, aplicando los métodos de los mínimos cuadrados y de los multiplicadores de Lagrange a las ecuaciones de balance, se desarrolla un procedimiento que minimiza las desviaciones e incongruencias en el balance de distribución de las clases granulométricas de los productos del esquema. Tomando como punto de partida los datos experimentales obtenidos por Coello (1993), se realiza la validación del procedimiento propuesto. Los resultados muestran que el procedimiento aplicado, permite el mejor ajuste cálculo de la carga circulante y a partir de sus valores, se recalculan los contenidos de las clases granulométricas de los productos del esquema que eliminan las incongruencias y errores de la distribución del contenido de las clases granulométricas generados en la toma y procesamiento general de las muestras.

B. Grocholski, K. Catalli, S. Shim et al.

D. Holwell, I. McDonald

The largest and most significant type of geological deposit of platinum group elements (PGEs) is that associated with magmatic base metal sulfide minerals in layered mafic or ultramafic igneous intrusions. The common association of PGEs with sulfide minerals is a result of processes of magmatic and sulfide liquid segregation and fractionation. The mineralogical nature of the ores is dependent on a number of factors during sulfide liquid fractionation. The most significant of these with regard to the mineralogy of the two most important metals, platinum and palladium, is the presence and concentration of semimetals such as bismuth and tellurium within the mineralising sulfide liquid. Whereas rhodium, iridium, osmium and ruthenium are almost always present in solid solution within the resultant base metal sulfide minerals; should sufficient semimetals be present, Pd and especially Pt will form discrete minerals (such as platinum bismuthides) around the margins of, and possibly away from, the sulfides.