Metals for an Electrifying Future
There is a rapidly growing demand for the "critical metals" that are needed electronics and ultra-strong magnets but there is also a huge demand for the bronze-age staple, copper, which we need for all the transmission wires, motor windings and transformers of our electrified, low-carbon economy.
Dietmar Müller, Jo Condon, Julian Diaz, and Rohitash Chandra explain how the EarthByte research group's virtual Earth lets us look deep below the surface and travel back in time. One of its many applications is to understand where copper deposits have formed along mountain belts.
Travelling through deep time to find copper for a clean energy future
Using geology and AI, a virtual model of how the Earth’s tectonic plates have evolved can help reveal deposits of copper.
The ConversationDietmar Müller
The peer-reviewed, research paper behind this article can be found here:
Predicting the emplacement of Cordilleran porphyry copper systems using a spatio-temporal machine learning model
Porphyry copper (Cu) systems occur along magmatic belts derived in subduction zones. Our current understanding of their formation is restricted to obs…
The Qinglong antimony deposit is located in the Nanpanjiang (Youjiang) basin, South China. The role of organic matter in antimony mineralisation is often discussed due to hydrocarbon gases within inclusions of antimony deposits, which have been detected since the 1990s. However, as no macroscopic or mass organic material has been discovered, the origin of such hydrocarbon gases and their potential relation to mineralisation remain unclear. The discovery of the Qinglong palaeo-oil reservoir has provided a new opportunity for further study of the relationship between organic matter and antimony mineralisation. Five samples of bitumen from the palaeo-oil reservoir and seven samples of Devonian source rocks from the northern part of an antimony mine were analysed for organic elements, total organic carbon, chloroform bitumen ‘A’ and its group compositions, bitumen/vitrinite reflectance (Rb/Ro), biomarkers, carbon isotopes, and Rock-Eval pyrolysis. Kerogen microscopy and rare earth elements (REEs) analysis were also performed on the Devonian source rocks samples. Finally, seven samples of pyrite coexisting with bitumen in the palaeo-oil reservoir were analysed using stable sulphur isotope analysis.Results show that the Devonian source rocks are rich in organic matter, yet it is well known that few residual organic matters are capable of continuing hydrocarbon generation after strong thermal evolution. Both the palaeo-oil reservoir and source rocks are found to have the same source of parent material and belong to the same mixed type of kerogen, and have reached the over-mature stage. The ratio of pristane/phytane (Pr/Ph) and the gammacerane index (Ga/C30H) indicate that the source rocks were formed in a reductive brackish water sedimentary environment, with a parameter nearly the same as that of the palaeo-oil reservoir. The palaeo-oil reservoir samples are highly consistent with the source rocks in terms of the source and type of organic matter, as well as the sedimentary environment, thermal maturity, normal alkanes, key fingerprint parameters, and grey relevancy degree of REEs. In addition, the carbon isotopes (δ13C) of bitumen range from − 28.75‰ to − 30.23‰, with an average of − 29.45‰, while those of the source rocks vary from − 25.20‰ to − 28.56‰, with an average of − 27.06‰, which are consistent with each other in the range of carbon isotope fractionation generated by the thermal evolution of organic matter. Therefore, it is determined that the palaeo-oil reservoir was derived from the Devonian oil-source rocks.The sulphur isotopes (δ34S) of pyrite associated with bitumen in the palaeo-oil reservoir have a relatively narrow range (−1.9‰ to 3.1‰, average 0.97‰), which are very close to those of sulphides in the mineralisation period of the gold and antimony deposits. We believe that the sulphur needed for mineralisation was mainly derived from hydrocarbon fluids in the basin and speculate that the palaeo-oil and hydrocarbon gases formed by thermal cracking and then served as a reducing agent to convert SO42− in the oilfield brine into reduced sulphur (S2−/HS−) through the thermochemical sulphate reduction (TSR) reaction. It is found that although the Qinglong palaeo-oil reservoir did not contribute Sb to the deposit (existing Sb was instead found to be from the Dachang member and its overlying basalt), it did, however, provided a reductive metallogenic environment and contributed a relatively large amount of reduced sulphur (S2−/HS−) to participate the mineralisation.Deep learning (DL) algorithms have a strong ability to recognize high-level features in geochemical exploration data and have been widely employed for the recognition of multivariate geochemical anomalies linked to mineralization. In this study, the adversarially learned anomaly detection (ALAD) algorithm, an improved generative adversarial network (GAN), was employed to detect multivariate geochemical anomalies related to mineralization. Compared with other unsupervised deep learning algorithms, ALAD significantly improves anomaly detection performance by combining the advantages of deep variational autoencoder and generative adversarial network. Various experiments were performed to construct a well-designed network structure to process high-dimensional geochemical data to identify geochemical anomalies linked to tungsten (W) polymetallic mineralization in the south of Jiangxi Province of China. The extracted geochemical anomalies have a high spatial distribution correction with the locations of the discovered W polymetallic mineralization. Both the area under the receiver operating characteristic curve and the prediction-area plot indicate a good performance of the ALAD model. Furthermore, the extracted geochemical anomalies are spatially correlated with granites which control the spatial distribution of W polymetallic mineralization. These observations indicate that, as an unsupervised deep learning algorithm, ALAD is useful for detecting geochemical anomalies associated with mineralization.A till geochemistry and indicator mineral (IM) study was carried out in the South Range of the Sudbury Igneous Complex (SIC) to develop surficial mineral exploration techniques that are suitable for low sulfide, high precious metal (LSHPM) and massive sulfide Ni-Cu-PGE mineralization. Surficial exploration in this region is problematic because of heterogeneous till deposits overlain by glaciolacustrine sediments, a naturally high surficial geochemical background, and a paucity of undisturbed till for geochemical sampling due to mining-related operations. The Vermilion and Crean Hill deposits were selected for this case study because their geology and mineralogy have been extensively studied. Pathfinder elements that show a strong, positive (r2 > 0.6, n = 120) correlation with ore elements Ni, Cu, Au and PGEs (Pt, Pd, Ru, Rh, and Ir), which are derived from mineralization and present in elevated concentrations in till samples overlying mineralization are As, Bi, Co, Cr, Pb, Sb and Te. Ore minerals that survive glacial transport and post-glacial weathering and are the best indicators of Ni-Cu-PGE-Au mineralization are grains of gold, chalcopyrite, and sperrylite, predominantly recovered from the < 0.25 mm pan concentrate fraction of till. Despite challenges, this study has identified new exploration targets that warrant further investigation and demonstrates that till geochemistry and IM methods can be used to explore for Ni-Cu-PGE mineralization in established mining camps.Carbonaceous debris (i.e., CD), dispersed organic matter (i.e., DOM) within sandstones, has been studied in the Shuanglong uranium deposit of the southern Ordos Basin, northern China. Relations of uranium enrichment and organic matter (i.e., OM) were investigated through maceral analyses, proximate analysis, vitrinite reflectance measurements, and morphology analyses of uranium minerals. The results show that CD widely distributed in sandstones, is associated with pyrite and uranium minerals. Macerals are mostly composed of telinite, collotelinite, collodetrinite, semifusinite, and inertodetrinite, including that collotelinite is dominant (contents more than 60%). The CD is at the stage of medium coalification, and is of low moisture, high ash, high volatile matter, medium fixed carbon, and high sulfur. Uranium occurs in uranium minerals (i.e., pitchblende and coffinite) and amorphous uranium. Moreover, uranium minerals partly or completely replace macerals. Statistical analyses show that porous inertinite and higher organic matter maturity is more advantageous to uranium enrichment. Additionally, uranium is unevenly distributed in macerals along certain directions, which is related to the physicochemical properties of macerals. Porous inertinite could provide channel for uranium-bearing fluid migration and space for uranium preconcentration. The CD at the stage of gas coal is of reducibility to be favorable for the forming of uranium minerals. Moreover, the relative atomic content of uranium (IV) increases with the increasing organic matter maturity. Uranium-bearing fluid could permeate into macerals under certain physical and chemical conditions, and react, i.e., adsorption followed by reduction. It is beneficial to comprehend the mechanism of uranium mineralization, providing certain guides for prospection.The Hegenshan-Heihe Suture (HHS) is regarded as the collision boundary between the Erguna-Xing’an and Songnen Blocks at the eastern segment of the Central Asian Orogenic Belt (CAOB). However, the convergent processes associated with these two blocks are still controversial due to the lack of definitive geological evidence (i.e., ophiolites, accretionary prisms), which leads to a poor understanding of the relevant metallogenic setting. This paper provides new geophysical constraints on the lithospheric structures of the northern HHS from Dashizhai to Heihe. By the comprehensive interpretation of two parallel deep seismic profiles, the Qiqihaer-Chaihe profile and the newly acquired Duobaoshan profile, the configuration of the subduction-trench-arc-back-arc systems are studied. The subducted continental margin of the Songnen Block is recognized by a set of westward dipping reflections with an apparent dip angle of 20 to 25°, while the accretion complex with a lateral extension of more than 70 km is inferred as an area of short reflections with a westward tendency. The magmatic arc belts and the back-arc area have a quite different seismic reflection patterns. The former are recognized by inverted triangular-shaped transparent reflections, while the latter is featured by arched reflections as clusters. They are bounded by a set of remarkable inclined reflections from the topmost crust to the bottom of the middle crust. It is inferred that the final subduction relict of the northern HHS went through Qiqihaer to the west of Sunwu. Magmatic arc belts forming over two stages are recognized to be located to the west of the subduction relict, and they have a consistent distribution with the magnetic anomaly. A detailed model of the formation of the northern HHS is proposed, which includes two stages of westward oceanic subduction and the final collision.The Hongtaiping Cu polymetallic deposit in Yanbian area (NE China) is located in the tectonic junction between the eastern Central Asian Orogenic Belt and the North China Craton. Two mineralization types are identified at the Hongtaiping deposit, i.e., stratiform mineralization hosted in the pyroclastic rocks of the Middle Permian Miaoling Formation (Fm.) and the quartz-sulfide vein-type mineralization controlled by fractures. To determine temporal and genetic relations between the two mineralization types, sulfide Rb–Sr dating and in-situ LA–ICP–MS trace element analysis were conducted. Seven sulfide samples from stratiform orebodies yielded a Rb–Sr isochron age of 268.3 ± 2.6 Ma, which is similar to the reported zircon U–Pb age of ore-hosting pyroclastic rocks of the Miaoling Fm., suggesting that the stratiform mineralization was syngenetic. The initial 87Sr/86Sr ratios of these sulfide samples show value of 0.7102–0.7103 (average of 0.7103), implying a major crustal origin, with certain mantle-derived input, for the ore-forming materials of the stratiform mineralization. Sulfides from the stratiform and vein-type ores have distinct trace elemental features. High Co/Ni ratio and low Se content in pyrite, and high Sn content and low Zn content in chalcopyrite reflect high temperature and vice versa. In the pyrite from stratiform and vein-type ores, average Se contents are 19.72 ppm and 9.70 ppm, and average Co/Ni ratios are 0.20 and 2.46, respectively. Whilst in the chalcopyrite from stratiform and vein-type ores, average Sn contents are 2.49 ppm and 60.31 ppm and average Zn contents are 346.55 ppm and 236.17 ppm, respectively, indicating that the temperature of the stratiform mineralization is lower than that of the vein-type mineralization. Integrating the geological and geochronological features of the two types of mineralization and wall rocks, as well as trace element compositions of the sulfides, we inferred that the stratiform mineralization at the Hongtaiping deposit can be classified as volcanogenic massive sulfide (VMS)-type, associated with the Middle Permian submarine volcanism caused by the subduction of the Paleo-Asian Ocean. The vein-type mineralization was likely related to the Late Triassic felsic magmatism. In a word, two-phase mineralization implies the VMS-hydrothermal reworking-type for the Hongtaiping deposit.Author links open overlay panelJulianDiaz-RodriguezaR. DietmarMülleraRohitashChandrabc
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