Search Results (5)

The Arabian–Nubian Shield (ANS) hosts numerous volcanogenic massive sulphide (VMS) deposits formed in submarine volcanic settings and enriched by hydrothermal processes, making it a critical region for mineral exploration due to the types of deposits it hosts and its geological complexity. The Wadi Bidah Mineral Belt (WBMB), located within the Arabian Shield, contains over 30 polymetallic VMS occurrences associated with an island arc system active between 950 and 800 million years ago. Despite its mineral potential, the WBMB still needs to be explored, with limited geophysical studies to support resource evaluation. This study focuses on the Hawiah area, a prominent VMS site within the WBMB, to delineate subsurface mineralization using transient electromagnetic (TEM) methods. TEM surveys were conducted to characterize the conductivity structure and identify potential zones of sulphide mineralization. Data were processed and inverted to generate 1D, 2D, and 3D resistivity models, providing critical insights into the depth, geometry, and continuity of the mineralized zones based on the final 3D resistivity distribution. The results revealed distinct conductive (very low resistivity) anomalies, correlating with known surface gossans and inferred sulphide-rich layers, and extended these features into the subsurface. The integration of TEM results with geological and geochemical data highlights the effectiveness of this approach in detecting and mapping concealed mineral deposits in complex geological environments. This study advances the understanding of VMS systems in the WBMB and demonstrates the potential of TEM surveys as a key tool for mineral exploration in the Arabian Shield. Full article

A comprehensive investigation into the application of machine learning algorithms for accurately classifying mineral deposit types is presented. The study specifically focuses on iron deposits in the Portuguese Ossa-Morena Zone, employing a limited dataset of trace element geochemistry from magnetites. The research aims to derive meaningful methodological and metallogenic conclusions from the obtained results. The findings demonstrate that the combination of a restricted dataset of trace element geochemistry from magnetites with diverse machine learning models serves as a reliable tool for achieving precise classifications of mineral deposit types. Among the machine learning methods evaluated, random forest, naïve Bayes, and multinomial logistic regression emerge as the most accurate classifiers, whereas the support vector machine, the k-nearest neighbour, and artificial neural networks exhibit lower performance scores. By integrating all literature-proposed classifications, and applying them to selected iron deposits, confident classifications were obtained. Alvito and Azenhas are reliably classified as skarns, whereas Monges, Serrinha, and Vale da Arca are classified as either porphyry or a Banded Iron Formation (BIF). Notably, the classification of Orada proves cryptic, encompassing both BIF and volcanogenic massive sulphide (VMS) deposit types. Moreover, the application of machine learning models to pertinent case studies offers valuable insights not only for classifying mineral deposit types but also for discerning mixed or complex origins. This approach provides meaningful results that can aid in the interpretation of mineral deposit types and may facilitate the identification of new mineral exploration targets. The research highlights the robustness of machine learning algorithms in interpreting magnetite data and underscores their potential significance in exploration projects. Full article

Gold, present as electrum, in the Battle Gap, Ridge North-West, HW, and Price deposits at the Myra Falls mine, occurs in late veinlets cutting the earlier volcanogenic massive sulphide (VMS) lithologies. The ore mineral assemblage containing the electrum comprises dominantly galena, tennantite, bornite, sphalerite, chalcopyrite, pyrite, and rarely stromeyerite, and is defined as an Au-Zn-Pb-As-Sb association. The gangue is comprised of barite, quartz, and minor feldspathic volcanogenic sedimentary rocks and clay, comprised predominantly of kaolinite with subordinate illite. The deposition of gold as electrum in the baritic upper portions of the sulphide lenses occurs at relatively shallow water depths beneath the sea floor. Primary, pseudosecondary, and secondary fluid inclusions, petrographically related to gold, show boiling fluid inclusion assemblages in the range of 123 to 173 °C, with compositions and eutectic melt temperatures consistent with seawater at approximately 3.2 wt % NaCl equivalent. The fluid inclusion homogenization temperatures are consistent with boiling seawater corresponding to water depths ranging from 15 to 125 m. Slightly more dilute brines corresponding to salinities of approximately 1 wt % NaCl indicate that there is input from very low-salinity brines, which could represent a transition from subaqueous VMS to epithermal-like conditions for precious metal enrichment, mixing with re-condensed vapor, or very low-salinity igneous fluids. Full article

The Permian (~273–274 Ma) Ice volcanogenic massive sulphide (VMS) deposit represents a mound shaped Cyprus (mafic)-type VMS deposit (~4.5 Mt @ 1.5% Cu) hosted in basaltic rocks of Slide Mountain terrane. The deposit consists of massive sulphides that are underlain by a chlorite-sulphide-hematite-rich stringer pipe, and overlain by a hematite-(pyrite)-rich exhalative chert. The sulphides are divided into five facies: (1) pyrite-rich; (2) pyrite-bornite-rich; (3) pyrite-chalcopyrite-rich; (4) hematite-pyrite; and (5) stringer sulphide. The sulphides have a distinct paragenetic and textural evolution in the massive sulphide that reflect: (1) an early, low temperature stage (<250 °C dominated by Fe-Zn-Cu-rich mineralization; (2) an intermediate, high temperature stage (>300 °C) dominated by Cu-Fe-rich mineralization; and (3) a late, low temperature phase (<150 °C) dominated by Fe-rich mineralization. In situ sulphur isotope data pyrite and chalcopyrite (by secondary ion mass spectrometry (SIMS)) range from δ³⁴S = +1.8‰ to +8.2‰, but vary as a function of paragenesis and temperature of deposition. Both early and late forming sulfides were dominated by sulphur from partial thermochemical sulphate reduction (TSR) of seawater sulfate, whereas intermediate, high temperature mineralization was dominated leached, igneous sulphur from basement rocks. These results are similar to modern seafloor vents and many ancient VMS deposits. Full article

In situ laser ablation quadrupole inductively coupled plasma mass spectrometry was used to measure Pb isotopes in galena. Data acquisition was optimized by adjusting spot size, energy density, and ablation time to obtain near steady-state low relative standard deviation (%RSD) signals. Standard-sample bracketing using in-house Broken Hill galena as external reference standard was used and offline data reduction was carried out using VizualAge for Iolite3. Using this methodology, galena grain in polished thin sections from selected massive sulphide deposits of the Bathurst Mining Camp, Canada, were tested and compared to previously published data. Absolute values and errors on the weighted mean of ~20 individual analyses from each sample compared favourably with whole-rock Pb-Pb isotope data. This approach provides a mean to obtain rapid, accurate, and moderately (0.1% 2σ) precise Pb isotope measurements in galena and is particularly well suited for exploratory or reconnaissance studies. Further refinement of this approach may be useful in exploration for volcanogenic massive sulphides deposits and might be a useful vectoring tool when complemented with other conventional exploration techniques. Full article