scholarly journals A Comparative Study of Porphyry-Type Copper Deposit Mineralogies by Portable X-ray Fluorescence and Optical Petrography

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 431 ◽  
Author(s):  
Connor Gray ◽  
Adrian Van Rythoven
Keyword(s):  
Mineral Exploration ◽  
Porphyry Copper ◽  
Fluorescence Analysis ◽  
Copper Deposit ◽  
Porphyry Copper Deposits ◽  
Rock Composition ◽  
X Ray ◽  
Core Logging ◽  
Ore Minerals ◽  
Optical Mineralogy

Porphyry-type deposits are crucial reserves of Cu and Mo. They are associated with large haloes of hydrothermal alteration that host particular mineral assemblages. Portable X-ray fluorescence analysis (pXRF) is an increasingly common tool used by mineral prospectors to make judgments in the field during mapping or core logging. A total of 31 samples from 13 porphyry copper deposits of the Western Cordillera were examined. Whole-rock composition was estimated over three points of analysis by pXRF. This approach attempts to capture the rapid and sometimes haphazard application of pXRF in mineral exploration. Modes determined by optical petrography were converted into bulk rock compositions and compared with those determined by pXRF. The elements S, Si, Ca, and K all were underestimated by optical mineralogy, and the elements Cu, Mo, Al, Fe, Mg, and Ti were overestimated by optical mineralogy when compared with pXRF results. Most of these porphyry samples occur in veined porphyritic quartz monzonite that is characteristic of these deposits. Sulfide and silicate vein stockworks are pervasive in most of the samples as well as dissemination of sulfides outwards from veinlets. Ore minerals present include chalcopyrite and molybdenite with lesser bornite. Chalcocite, digenite, and covellite are secondary. Potential sources of analytical bias are discussed.

Exhumation and Preservation of Paleozoic Porphyry Cu Deposits: Insights from the Yandong Deposit, Southern Central Asian Orogenic Belt

2021 ◽  
Author(s):  
Lin Gong ◽  
Barry P. Kohn ◽  
Zhiyong Zhang ◽  
Bing Xiao ◽  
Lin Wu ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Mineral Exploration ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Porphyry Copper Deposits ◽  
Copper Deposits ◽  
Central Asian ◽  
Chinese Tianshan

Abstract Paleozoic porphyry copper deposits are generally much less common than their Mesozoic or Cenozoic counterparts, as they can be completely eroded in rapidly uplifting arcs. There are, however, some large Paleozoic porphyry copper deposits preserved worldwide, especially in the Central Asian orogenic belt, although the processes by which these ancient porphyry deposits were preserved are poorly constrained. The Carboniferous Yandong porphyry copper deposit was selected as a case study to resolve this issue using a combination of thermal history models derived from low-temperature thermochronology data and regional geologic records. Our results show that Yandong preserves a record of at least two episodes of cooling separated by a phase of mild Middle Jurassic reheating. These two cooling events included one major event, linked to the Qiangtang collision or northward motion of Tarim plate during the late Permian to Triassic, and one minor event, possibly related to the Lhasa collision or closure of Mongol-Okhotsk Ocean from the Middle Jurassic to Early Cretaceous, respectively. Tectonic quiescence and limited exhumation prevailed from the Late Cretaceous to Cenozoic in the Yandong area. Combining our results with regional geologic records, we propose that extensional tectonic subsidence, postmineralization burial, dry paleoclimatic conditions, and Cenozoic tectonic quiescence were key factors for the preservation of Yandong. This study demonstrates that anomalously old apatite fission track ages, integrated with age-elevation relationships, can have implications for mineral exploration strategies in the Chinese Tianshan orogens.

Zircon Petrochronology of the Meghri-Ordubad Pluton, Lesser Caucasus: Fingerprinting Igneous Processes and Implications for the Exploration of Porphyry Cu-Mo Deposits

2019 ◽  
Vol 114 (7) ◽  
pp. 1365-1388 ◽  
Author(s):  
Hervé Rezeau ◽  
Robert Moritz ◽  
Jörn-Frederik Wotzlaw ◽  
Samvel Hovakimyan ◽  
Rodrik Tayan
Keyword(s):  
Trace Element ◽  
Mineral Exploration ◽  
Porphyry Copper ◽  
Trace Element Composition ◽  
Element Composition ◽  
Porphyry Copper Deposits ◽  
Copper Deposits ◽  
Magmatic Processes ◽  
Lesser Caucasus ◽  
Intrusive Suite

Abstract The trace element composition of zircon, especially in tandem with U-Pb geochronology, has become a powerful tool for tracing magmatic processes associated with the formation of porphyry copper deposits. However, the use of the redox-sensitive Eu and Ce anomalies as a potential mineral exploration proxy is controversial. This study presents a comprehensive, temporally constrained data set of zircon trace element compositions (n = 645) for three compositionally distinct magmatic series identified in the Meghri-Ordubad pluton, southernmost Lesser Caucasus. The 30 million years of Cenozoic magmatism in the Meghri-Ordubad pluton are associated with several ore-forming pulses leading to the formation of porphyry copper deposits and epithermal-style mineralization. Our zircon geochemical data constrain the thermal and chemical evolution of this complex intrusive suite and allow an evaluation of the usefulness of zircon as a mineral exploration proxy for porphyry copper deposits. Our results combined with Rayleigh fractionation modeling indicate that the trace element composition of zircon (Th/U, Hf, Ti, YbN/DyN, Eu anomalies) is influenced by the composition and the water concentration of the parental magma, as well as by co-crystallizing titanite and apatite. In contrast, the variations of Ce anomalies remain difficult to explain by magmatic processes and could rather be ascribed to relative fluctuations of the redox conditions. In the Meghri-Ordubad pluton, we do not observe any systematic patterns between the trace element composition in zircons and the different ore-forming pulses. This questions the reliability of using the trace element composition in zircon as an exploration mineral proxy, and it rather emphasizes that a good knowledge of the entire magmatic evolution of a metallogenic province is required.

scholarly journals A new model for the optimal structural context for giant porphyry copper deposit formation

Geology ◽  
2021 ◽  
Author(s):  
José Piquer ◽  
Pablo Sanchez-Alfaro ◽  
Pamela Pérez-Flores
Keyword(s):  
Mineral Exploration ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Structural Data ◽  
Hydrothermal Systems ◽  
Fault System ◽  
Magma Ascent ◽  
Common View ◽  
New Model ◽  
Structural Context

Porphyry-type deposits are the main global source of copper and molybdenum. An improved understanding of the most favorable structural settings for the emplacement of these deposits is necessary for successful exploration, particularly considering that most future discoveries will be made under cover based on conceptual target generation. A common view is that porphyry deposits are preferentially emplaced in pull-apart basins within strike-slip fault systems that favor local extension within a regional compressive to transpressive tectonic regime. However, the role of such a structural context in magma storage and evolution in the upper crust remains unclear. In this work, we propose a new model based on the integration of structural data and the geometry of magmatic-hydrothermal systems from the main Andean porphyry Cu-Mo metallogenic belts and from the active volcanic arc of southern Chile. We suggest that the magma differentiation and volatile accumulation required for the formation of a porphyry deposit is best achieved when the fault system controlling magma ascent is strongly misoriented for reactivation with respect to the prevailing stress field. When magmas and fluids are channeled by faults favorably oriented for extension (approximately normal to σ3), they form sets of parallel, subvertical dikes and veins, which are common both during the late stages of the evolution of porphyry systems and in the epithermal environment. This new model has direct implications for conceptual mineral exploration.

scholarly journals The history of mining and mineral exploration in Panama: From Pre-Columbian gold mining to modern copper mining

2020 ◽  
Vol 72 (3) ◽  
pp. A180720
Author(s):  
Stewart D. Redwood
Keyword(s):  
Gold Mining ◽  
Mineral Exploration ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Gold Deposits ◽  
Stream Sediment ◽  
Gold Mine ◽  
Foreign Companies ◽  
Current Period ◽  
History Of

The history of mining and exploration in Panama is a case study of the evolution of mining in a tropical, island arc environment in the New World from prehistoric to modern times over a period of ~1900 years. Panama has a strong mineral endowment of gold (~984 t), and copper (~32 Mt) resulting in a rich mining heritage. The mining history can be divided into five periods. The first was the pre-Columbian period of gold mining from near the start of the Current Era at ~100 CE to 1501, following the introduced of gold metalwork fully fledged from Colombia. Mining of gold took place from placer and vein deposits in the Veraguas, Coclé, Northern Darien and Darien goldfields, together with copper for alloying. Panama was the first country on the mainland of the Americas to be mined by Europeans during the Spanish colonial period from 1501-1821. The pattern of gold rushes, conquest and settlement can be mapped from Spanish records, starting in Northern Darien then moving west to Panama in 1519 and Nata in 1522. From here, expeditions set out throughout Veraguas over the next century to the Veraguas (Concepción), Southern Veraguas, Coclé and Central Veraguas goldfields. Attention returned to Darien in ~1665 and led to the discovery of the Espíritu Santo de Cana gold mine, the most important gold mine to that date in the Americas. The third period was the Republican period following independence from Spain in 1821 to become part of the Gran Colombia alliance, and the formation of the Republic of Panama in 1903. This period up to ~1942 was characterized by mining of gold veins and placers, and manganese mining from 1871. Gold mining ceased during World War Two. The fourth period was the era of porphyry copper discoveries and systematic, regional geochemical exploration programs from 1956 to 1982, carried out mainly by the United Nations and the Panamanian government, as well as private enterprise. This resulted in the discovery of the giant porphyry copper deposits at Cerro Colorado (1957) and Petaquilla (Cobre Panama, 1968), as well as several other porphyry deposits, epithermal gold deposits and bauxite deposits. The exploration techniques for the discovery of copper were stream sediment and soil sampling, followed rapidly by drilling. The only mine developed in this period was marine black sands for iron ore (1971-1972). The fifth and current period is the exploration and development of modern gold and copper mines since 1985 by national and foreign companies, which started in response to the gold price rise. The main discovery methods for gold, which was not analyzed in the stream sediment surveys, were lithogeochemistry of alteration zones and reexamination of old mines. Gold mines were developed at Remance (1990-1998), Santa Rosa (1995-1999 with restart planned in 2020) and Molejon (2009-2014), and the Cobre Panama copper deposit started production in 2019. The level of exploration in the country is still immature and there is high potential for the discovery of new deposits.

HYPOGENE ALUNITE FROM THE EL SALVADOR DISTRICT, CHILE, INDICATES POTENTIAL FOR A BLIND PORPHYRY COPPER CENTER

2020 ◽  
Vol 115 (2) ◽  
pp. 231-239 ◽  
Author(s):  
Jeffrey W. Hedenquist ◽  
Yasushi Watanabe ◽  
Antonio Arribas
Keyword(s):  
El Salvador ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Hydrothermal Activity ◽  
Porphyry Copper Deposits ◽  
Copper Ore ◽  
Copper Mineralization ◽  
Alteration Minerals ◽  
Porphyry Copper Mineralization ◽  
Granodiorite Porphyry

Abstract Surface samples of hypogene alunite that cement late breccia bodies from the El Salvador porphyry copper district of Chile were recently dated. One alunite sample over the principal Turquoise Gulch porphyry deposit has a 40Ar/39Ar total gas age of 40.64 ± 1.04 Ma, overlapping the age of a late latite intrusion. Two other samples associated with quartz-alunite replacement of rhyolite, ~750 m southwest of the collapse zone over the block cave of the porphyry copper deposit, are distinctly younger, at 38.12 ± 0.66 and 38.04 ± 0.22 Ma (averages of duplicate analyses, with ±2σ errors). Previously reported U/Pb ages of zircons from 15 Eocene-age diorite, granodiorite, and granite porphyry intrusions have weighted mean ages that range from about 44 to 41 Ma, with peak magmatic flux interpreted at 44 to 43 Ma. Porphyry copper ores in the El Salvador district formed at about the same time as porphyry intrusions, with intrusive centers that migrated in a south-southwest direction, from the small deposits at Cerro Pelado (~44.2 Ma), to Old Camp (~43.6 Ma) and M Gulch-Copper Hill (~43.5–43.1 Ma), to the main ore deposit at Turquoise Gulch (~42 Ma). The granodiorite porphyry intrusions at Turquoise Gulch are associated with ~80% of the known copper ore of the district; they record waning stages of magmatism at 42.5 to 42.0 Ma, followed by weakly altered latite dikes at 41.6 Ma. Molybdenite in quartz veins returned Re-Os ages of 41.8 to 41.2 Ma. The two alunite samples from our study with coincident dates of ~38 Ma provide evidence for magmatic-hydrothermal activity younger than any recognized to date, consistent with the alteration overprint of quartz-alunite on older muscovite after erosion. This younger activity must have been associated with a blind intrusion, likely located south of the Turquoise Gulch deposit, based on the distribution of alteration minerals, and offset from the zoning associated with the Turquoise Gulch center. Stable isotope values (δ34S, δ18O, δD) of the ~38 Ma alunite indicate a high-temperature hypogene origin, consistent with formation in a lithocap environment that typically is located at shallow levels over and on the shoulders of porphyry copper deposits. Both observations—alteration overprint and markedly younger age of alunite—indicate the potential for porphyry copper mineralization south of Granite Gulch, as much as 1,000 m below the level of the coeval outcropping quartz-alunite replacement, perhaps near ~2,000-m elevation; this is hundreds of meters deeper than the known copper ore of Turquoise Gulch.

scholarly journals Magma Emplacement Rates and Porphyry Copper Deposits: Thermal Modeling of the Yerington Batholith, Nevada

2017 ◽  
Vol 112 (7) ◽  
pp. 1653-1672 ◽  
Author(s):  
Anne Schöpa ◽  
Catherine Annen ◽  
John H. Dilles ◽  
R. Stephen J. Sparks ◽  
Jon D. Blundy
Keyword(s):  
Porphyry Copper ◽  
Copper Deposit ◽  
Porphyry Copper Deposit ◽  
Testable Hypothesis ◽  
Porphyry Copper Deposits ◽  
Magma Chambers ◽  
Deposit Formation ◽  
Slow Cooling ◽  
Copper Deposits ◽  
Magma Emplacement

Abstract Many porphyry copper deposits are associated with granitoid plutons. Porphyry copper deposit genesis is commonly attributed to degassing of pluton-forming intermediate to silicic magma chambers during slow cooling and crystallization. We use numerical simulations of thermal evolution during pluton growth to investigate the links between pluton construction, magma accumulation and solidification, volatile release, and porphyry copper deposit formation. The Jurassic Yerington batholith, Nevada, serves as a case study because of its exceptional exposure, revealing the geometry of three main intrusions. The last intrusion, the Luhr Hill granite, is associated with economic porphyry copper deposits localized over cupolas where dikes and fluid flow were focused. Our simulations for the conceptual model linking porphyry copper deposits with the presence of large, highly molten magma chambers show that the Luhr Hill granite must have been emplaced at a vertical thickening rate of several cm/yr or more. This magma emplacement rate is much higher than the time-averaged formation rates of other batholiths reported in the literature. Such low rates, although common, do not lead to magma accumulation and might be one of the reasons why many granitoid plutons are barren. Based on our results, we formulate the new testable hypothesis of a link between porphyry copper deposit formation and the emplacement time scale of the associated magma intrusion.

Trace Analytical Capabilities of Total-Reflection X-ray Fluorescence Analysis

1984 ◽  
Vol 28 ◽  
pp. 75-83 ◽  
Author(s):  
W. Michaelis ◽  
J. Knoth ◽  
A. Prange ◽  
H. Schwenke
Keyword(s):  
Analytical Chemistry ◽  
Mechanical Design ◽  
Mineral Exploration ◽  
Fluorescence Analysis ◽  
Total Reflection ◽  
Environmental Research ◽  
X Rays ◽  
X Ray ◽  
Long Time ◽  
Preparation Techniques

AbstractThe principle to utilize total reflection of the primary X-rays in fluorescence analysis is known since a lot of years. Nevertheless, analytical chemistry did not profit from the inherent advantages of the method for a long time. The main reason for this failure was the lack of instruments which were easy to use in practice. A few years ago, however, the development of a proper mechanical design and of adapted sample preparation techniques led to commercially available spectrometers which throughout fulfill the demands for routine applications. Since then the utilization of Total-Reflection X-Ray Fluorescence Analysis (TXRF) has increased rapidly. The scope of work is meanwhile widespread over environmental research and monitoring, mineralogy, mineral exploration, oceanography, biology, medicine and biochemistry. Accordingly, numerous matrices have been handled.

scholarly journals Mineralogical Setting of Precious Metals at the Assarel Porphyry Copper-Gold Deposit, Bulgaria, as Supporting Information for the Development of New Drill Core 3D XCT-XRF Scanning Technology

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 946
Author(s):  
Mihaela-Elena Cioacă ◽  
Marian Munteanu ◽  
Edward P. Lynch ◽  
Nikolaos Arvanitidis ◽  
Mikael Bergqvist ◽  
...  
Keyword(s):  
Porphyry Copper ◽  
Precious Metals ◽  
Copper Deposit ◽  
Drill Core ◽  
X Ray ◽  
Physicochemical Changes ◽  
Multi Stage ◽  
Xrf Scanning ◽  
Copper Gold ◽  
Metallogenic Zone

A petrographic investigation of ore samples from the Assarel porphyry copper deposit in the Srednogorie metallogenic zone (Bulgaria) constrains the setting and character of precious metals (Au, Ag, PGE) and related minerals within the deposit. This work supports renewed interest in understanding the deportment of precious metals and provides mineralogical knowledge during the testing and validation of novel drill core 3D X-ray computed tomography–X-ray fluorescence (XCT-XRF) scanning technology being developed as part of the X-MINE project. Scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) results indicate precious metals occur in their native state (Au, Ag), as sulfides (Ag), sulfosalts (Au), tellurides (Ag, Pd), and selenides (Ag), and typically form micron-sized inclusions in pyrite and chalcopyrite or are disseminated in the groundmass of the rock. Preservation of early Fe oxide–chalcopyrite ± bornite assemblage as relics in the more dominant pyrite-chalcopyrite mineralization assemblage supports mineral disequilibrium relationships and multi-stage mineralization events. Several rare minerals (e.g., merenskyite, acanthite, sorosite, tetra-auricupride, auricupride, greenokite, bismuthinite, nagyagite, native Ni) are reported for the first time at Assarel and highlight the mineralogical diversity of the ore. The occurrence of precious metals and related minerals at Assarel attest to a complex hydrothermal system that underwent progressive physicochemical changes during the evolution of the mineralizing system (e.g., redox conditions, fluid chemistry).

scholarly journals TARGETING HYDROTHERMAL ALTERATIONS UTILIZING LANDSAT-8 ANDASTER DATA IN SHAHR-E-BABAK, IRAN

2017 ◽  
Vol XLII-4/W5 ◽  
pp. 153-157
Author(s):  
M. Safari ◽  
A. B. Pour ◽  
A. Maghsoudi ◽  
M. Hashim
Keyword(s):  
Mineral Exploration ◽  
Porphyry Copper ◽  
Color Space ◽  
Sensor Data ◽  
Color Contrast ◽  
Landsat 8 ◽  
Porphyry Copper Deposits ◽  
Alteration Zones ◽  
Magmatic Arc ◽  
Band Combinations

Shahr-e-Babak tract of the Kerman metalogenic belt is one of the most potential segments of Urumieh–Dokhtar (Sahand-Bazman) magmatic arc. This area encompasses several porphyry copper deposits in exploration, development and exploitation hierarchy. The aim of this study is to map hydrothermal alterations caused by early Cenozoic magmatic intrusions in Shahr-e-Babak area. To this purpose, mineral mapping methods including band combinations, ratios and multiplications as well as PCA and MNF data space transforms in SWIR and VNIR for both ASTER and OLI sensors. Alteration zones according to spectral signatures of each type of alteration mineral assemblages such as argillic, phyllic and propylitic are successfully mapped. For enhancing the target areas false color composites and HSI-RGB color space transform are performed on developed band combinations. Previous studies have proven the robust application of ASTER in geology and mineral exploration; nonetheless, the results of this investigation prove applicability of OLI sensor from landsat-8 for alteration mapping. According to the results, evidently OLI sensor data can accurately map alteration zones. Additionally, the 12-bit quantization of OLI data is its privilege over 8-bit data of ASTER in VNIR and SWIR, thus OLI high quality results, which makes it easy to distinguish targets with enhanced color contrast between the altered and unaltered rocks.

scholarly journals Application of Dirichlet Process and Support Vector Machine Techniques for Mapping Alteration Zones Associated with Porphyry Copper Deposit Using ASTER Remote Sensing Imagery

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1235
Author(s):  
Mastoureh Yousefi ◽  
Seyed Hasan Tabatabaei ◽  
Reyhaneh Rikhtehgaran ◽  
Amin Beiranvand Pour ◽  
Biswajeet Pradhan
Keyword(s):  
Hydrothermal Alteration ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Porphyry Copper Deposit ◽  
Training Data ◽  
Support Vector ◽  
Porphyry Copper Deposits ◽  
Copper Deposits ◽  
Alteration Zones ◽  
Hydrothermal Alteration Zones

The application of machine learning (ML) algorithms for processing remote sensing data is momentous, particularly for mapping hydrothermal alteration zones associated with porphyry copper deposits. The unsupervised Dirichlet Process (DP) and the supervised Support Vector Machine (SVM) techniques can be executed for mapping hydrothermal alteration zones associated with porphyry copper deposits. The main objective of this investigation is to practice an algorithm that can accurately model the best training data as input for supervised methods such as SVM. For this purpose, the Zefreh porphyry copper deposit located in the Urumieh-Dokhtar Magmatic Arc (UDMA) of central Iran was selected and used as training data. Initially, using ASTER data, different alteration zones of the Zefreh porphyry copper deposit were detected by Band Ratio, Relative Band Depth (RBD), Linear Spectral Unmixing (LSU), Spectral Feature Fitting (SFF), and Orthogonal Subspace Projection (OSP) techniques. Then, using the DP method, the exact extent of each alteration was determined. Finally, the detected alterations were used as training data to identify similar alteration zones in full scene of ASTER using SVM and Spectral Angle Mapper (SAM) methods. Several high potential zones were identified in the study area. Field surveys and laboratory analysis were used to validate the image processing results. This investigation demonstrates that the application of the SVM algorithm for mapping hydrothermal alteration zones associated with porphyry copper deposits is broadly applicable to ASTER data and can be used for prospectivity mapping in many metallogenic provinces around the world.

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