地球科学最新文献

{"title":"Mars' Hourglass Landforms as Local Source-to-Sink Fluvial Systems","authors":"A. S. Zaki,&nbsp;D. Wang,&nbsp;S. R. Baker,&nbsp;J. P. Grotzinger,&nbsp;J. Dickson,&nbsp;M. P. Lamb","doi":"10.1029/2024JE008745","DOIUrl":"https://doi.org/10.1029/2024JE008745","url":null,"abstract":"<p>Mars' landscapes offer enigmatic clues about a once wetter climate. Particularly puzzling are hourglass landforms, distinguished by two small (10–100 s km²) branching ridge systems connected by a narrow neck. This geometry resembles a source-to-sink fluvial system, but occurs on relatively flat terrain without a clear drainage direction. Here, we characterize 13 hourglass landforms and branched ridge networks that occur near the crustal dichotomy boundary and compare them with flume experiments and terrestrial analogs. We find that hourglass landforms are composed of branching and sinuous fluvial ridges, indicating that they are ancient river deposits exposed in positive relief due to substantial differential erosion. Typically, one side of the hourglass is composed of a ridge network with larger and more distinct ridges (type 1), whereas the other network has smaller cross-cutting ridges (type 2). In some cases, a remnant crater rim divides the two sides, with the type 1 network eroded into the crater wall, indicating a drainage network, and the type 2 network bounded by the crater, indicating an alluvial fan. Results indicate hourglass landforms are eroded remnants of small catchment-fan drainage systems that have experienced major climate change. They formed following impact cratering in a wet climate by runoff or seepage erosion where the crater breached the groundwater table. Subsequent wind erosion in a dry climate created ridge networks and completely removed the antecedent catchment-fan topography. Our findings on the distinction between different types of hourglass networks may help differentiate distributary from tributary networks in fluvial ridge systems elsewhere on Mars.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008745","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Strong Impact of Precipitation Intensity on Groundwater Recharge and Terrestrial Water Storage Change in Arizona, a Typical Dryland","authors":"Yuan Qiu,&nbsp;James S. Famiglietti,&nbsp;Ali Behrangi,&nbsp;Mohammad Ali Farmani,&nbsp;Hossein Yousefi Sohi,&nbsp;Aniket Gupta,&nbsp;Fengwei Hung,&nbsp;Karem Abdelmohsen,&nbsp;Guo-Yue Niu","doi":"10.1029/2025GL114747","DOIUrl":"https://doi.org/10.1029/2025GL114747","url":null,"abstract":"<p>This study demonstrates the critical role of precipitation intensity in groundwater recharge generation and terrestrial water storage (TWS) change. We conducted two experiments driven by precipitation products with close annual totals but distinct intensity in Arizona, using the Noah-MP model with advanced soil hydrology. The experiment with higher precipitation intensity (EXP_HI) produces an annual groundwater recharge of 6.91 mm/year in Arizona during 2001–2020, ∼15 times that of the experiment with lower precipitation intensity (EXP_LI). Correspondingly, EXP_LI produces a declining groundwater storage (GWS) trend of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 </mrow>\u0000 <annotation> ${-}$</annotation>\u0000 </semantics></math>0.51 mm/month, nearly triple that of EXP_HI. GWS change dominates the TWS trend. EXP_LI shows a declining TWS trend of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 </mrow>\u0000 <annotation> ${-}$</annotation>\u0000 </semantics></math>0.57 mm/month, nearly twice that of EXP_HI. Higher precipitation intensity reduces evapotranspiration and enhances infiltration and percolation, allowing more precipitation to recharge groundwater. This study underscores the need to ensure the accuracy of precipitation intensity in hydrological modeling for reliable water resources assessment and projection.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 14","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL114747","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enigmatic High-Tenor Rh-, Ru-, Ir-, and Os-Rich Base Metal Sulfide Mineralization Within the Northern Limb of the Bushveld Complex: A Product of Fractionation of a Sulfide Liquid?","authors":"Kate R. Canham, David A. Holwell, Lara Du Preez, Paul AM. Nex, Allan H. Wilson, Katie McFall, Erin S. Thompson, Hannah SR. Hughes, Andy Lloyd","doi":"10.5382/econgeo.5159","DOIUrl":"https://doi.org/10.5382/econgeo.5159","url":null,"abstract":"The Base Metal zone at Sandsloot in the Northern limb of the Bushveld Complex, South Africa, is a highly unusual and high-grade Os-Ir-Ru-Rh, Fe-Ni sulfide-rich horizon hosted within the deep Platreef, below the main platinum group element (PGE) horizon. The Base Metal zone ranges from 5 to 100 meters in thickness and is located up to 150 meters beneath the PGE reef. Base metal sulfide mineralization occurs as disseminated/blebby to semimassive/massive sulfides, with a typical assemblage of ~60/25/15 pyrrhotite/pentlandite/chalcopyrite modal %. The Base Metal zone is characterized by high (Os + Ir + Ru + Rh)/(Pt + Pd) ratios that reflect monosulfide solid solution, primitive mantle-normalized PGE profiles. The PGM assemblage is dominated by laurite (RuS2) (62% by area) and iridium-group platinum group element (IPGE) + Pt arsenosulfides (21% by area). The PGE tenors of the sulfides vary between different textural styles, either reflecting R-factor variations or dilution of tenors by addition of crustal S. Disseminated/blebby sulfides have the highest tenors (up to 153 ppm Pd, 249 ppm Rh, 818 ppm Ru), whereas semimassive/massive sulfides have lower tenors (up to 2.8 ppm Pd, 1.8 ppm Pt, 11 ppm Rh, 17 ppm Ru, 2.2 ppm Os, 3.5 ppm Ir). The PGE geochemistry, IPGE-dominant platinum group metal (PGM) assemblage, abundance of Fe sulfides, and high Ni/Cu ratios are consistent with the Base Metal zone representing the monsulfide solid solution portion of a sulfide liquid formed by fractional crystallization. Furthermore, the Cu + Pt + Pd + Au-poor nature of the Base Metal zone suggests that these metals were removed from the Base Metal zone, and some Cu-rich veins and sections are present around the margins of Ni-Fe sulfide to support this. Increasing Pd/Ir and decreasing Rh/Cu ratios downhole indicate the sulfide liquid fractionated downward. Therefore, a residual Cu-rich liquid, with associated Pt + Pd + Au, likely separated from monosulfide solid solution and was mobilized downward and away from the Base Metal zone. Significantly, the mobilization of a Cu-rich liquid leaves the possibility that an undiscovered Cu + Pt + Pd + Au orebody may exist at depth.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"57 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144712302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ocean Emulation With Fourier Neural Operators: Double Gyre","authors":"Suyash Bire,&nbsp;Björn Lütjens,&nbsp;Kamyar Azizzadenesheli,&nbsp;Animashree Anandkumar,&nbsp;Chris Hill","doi":"10.1029/2023MS004137","DOIUrl":"https://doi.org/10.1029/2023MS004137","url":null,"abstract":"<p>A data-driven emulator for the baroclinic double gyre ocean simulation is presented in this study. Traditional numerical simulations using partial differential equations (PDEs) often require substantial computational resources, hindering real-time applications and inhibiting model scalability. This study presents a novel approach employing Fourier neural operators to address these challenges in an idealized double-gyre ocean simulation. We propose a deep learning approach capable of learning the underlying dynamics of the ocean system, complementing the classical methods. Additionally, we show how Fourier neural operators allow us to train the network at one resolution and generate ensembles at a different resolution. We find that there is an intermediate time scale where the prediction skill is maximized.</p>","PeriodicalId":14881,"journal":{"name":"Journal of Advances in Modeling Earth Systems","volume":"17 7","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023MS004137","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Uncertainty-Aware Machine Learning Bias Correction and Filtering for OCO-2: 1","authors":"Steffen Mauceri,&nbsp;William Keely,&nbsp;Josh Laughner,&nbsp;Christopher W. O’Dell,&nbsp;Steven Massie,&nbsp;Robert Nelson,&nbsp;David Baker,&nbsp;Matthäus Kiel,&nbsp;Otto Lamminpää,&nbsp;Jonathan Hobbs,&nbsp;Abhishek Chatterjee,&nbsp;Tommy Taylor,&nbsp;Paul Wennberg,&nbsp;Sean Crowell,&nbsp;Britton Stephens,&nbsp;Vivienne H. Payne","doi":"10.1029/2025EA004328","DOIUrl":"https://doi.org/10.1029/2025EA004328","url":null,"abstract":"<p>The Orbiting Carbon Observatory-2 (OCO-2) makes space-based radiance measurements of reflected sunlight. Using a physics-based retrieval algorithm, these measurements are inverted to estimate column-averaged atmospheric carbon dioxide dry-air mole fractions (XCO₂). However, biases are present in the retrieved XCO₂ due to sensor calibration errors and discrepancies between the physics-based retrieval and nature. We propose a Random Forest (RF), a non-linear, interpretable machine learning (ML) technique, to correct these biases. The approach is rigorously validated, comes with quantified uncertainties, and is derived independent of carbon flux models. Compared to the operational approach, our method reduces unphysical variability over land and ocean and shows closer agreement with independent ground-based observations from the Total Carbon Column Observing Network. The RF-bias correction is suitable for integration into the operational processing pipeline for the next version of OCO-2 products, pending additional testing and validation. It is inherently generalizable to other existing and planned greenhouse gas monitoring missions. This paper (Part 1) describes the RF bias correction, while a second paper (Part 2) describes the development of a data filtering strategy specifically designed for a subset of retrievals exhibiting irreducible errors that remain inadequately corrected by the ML bias correction.</p>","PeriodicalId":54286,"journal":{"name":"Earth and Space Science","volume":"12 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025EA004328","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controls of Gouge Heterogeneity on Cyclic Reactivation of Fault-Valve Systems","authors":"Zhen Zhong,&nbsp;Zheye Song,&nbsp;Bo Li,&nbsp;Derek Elsworth,&nbsp;Yunjin Hu,&nbsp;Fengshou Zhang,&nbsp;Zhiyuan Chen","doi":"10.1029/2025GL115092","DOIUrl":"https://doi.org/10.1029/2025GL115092","url":null,"abstract":"<p>Fault zones are inherently heterogeneous and exert significant impacts on fluid injection-induced activities. We conducted Low-velocity shear experiments on homogeneous (HM) and layered (LM) clay-quartz mixtures representing gouge heterogeneity under double direct-shear and constant fluid injection. Cyclic fault-valve is activated in LM faults when the clay content is ≥50%, while it is absent in HM faults. A segmental layer of low-permeability clay perpendicular to the flow direction acts as a fault-valve, causing cyclic build-up then dissipation in pore pressure, hence influencing the magnitude of shear stress drop and sliding distance associated with seismic magnitudes. Recovered seismic moments from individual fault-valve cycles are bounded by the maximum seismic moment <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msubsup>\u0000 <mi>M</mi>\u0000 <mn>0</mn>\u0000 <mi>max</mi>\u0000 </msubsup>\u0000 <mo>=</mo>\u0000 <mfrac>\u0000 <mi>c</mi>\u0000 <mrow>\u0000 <mn>2</mn>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mrow>\u0000 <mn>1</mn>\u0000 <mo>−</mo>\u0000 <mi>c</mi>\u0000 </mrow>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 </mrow>\u0000 </mfrac>\u0000 <mi>G</mi>\u0000 <mo>∆</mo>\u0000 <msup>\u0000 <mi>V</mi>\u0000 <mo>′</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${M}_{0}^{max }=frac{c}{2(1-c)}Gmathit{{increment}}{V}^{mathit{prime }}$</annotation>\u0000 </semantics></math> when a pre-stress coefficient <i>c</i> ranges 90–99%. This study highlights the role of spatial distributions in pore pressure as controlled by gouge compositions and spatial heterogeneity on slip stability, and verifies the applicability of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msubsup>\u0000 <mi>M</mi>\u0000 <mn>0</mn>\u0000 <mi>max</mi>\u0000 </msubsup>\u0000 <mo>−</mo>\u0000 <mo>∆</mo>\u0000 <msup>\u0000 <mi>V</mi>\u0000 <mo>′</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${M}_{0}^{max }-mathit{{increment}}{V}^{mathit{prime }}$</annotation>\u0000 </semantics></math> relation to fault-valve systems.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 14","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL115092","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Ediacaran vendotaenid fossils from North Gondwana margin (Anti-Atlas, Morocco): Spatiotemporal distribution and stratigraphic significance","authors":"Kai Chen ,&nbsp;Aihua Yang ,&nbsp;El Hafid Bouougri ,&nbsp;Fangchen Zhao ,&nbsp;Chunlin Hu ,&nbsp;Bing Pan ,&nbsp;Chuan Yang ,&nbsp;Bo Chen ,&nbsp;Tianchen He ,&nbsp;Xiaojuan Sun ,&nbsp;Yiwei Xiong ,&nbsp;Maoyan Zhu","doi":"10.1016/j.precamres.2025.107882","DOIUrl":"10.1016/j.precamres.2025.107882","url":null,"abstract":"<div><div><em>Vendotaenia</em>, a simple ribbon-like fossil, is classified within the informal vendotaenid group alongside morphologically similar fossils. These fossils, which are frequently encountered near the Precambrian-Cambrian boundary, have been hypothesized to possess potential for stratigraphic correlation. However, their taxonomy is often ambiguous and the occurrences in older strata challenge their biostratigraphic significance. In this study, we first report vendotaenid fossils from the Late Ediacaran Tabia Member of the Adoudou Formation in Morocco. Based on meticulous morphological examination of the abundant specimens, these fossils are identified into three distinct morphological taxa, including <em>Vendotaenia</em>, characterized by a constant width and smooth curvature; <em>Tyrasotaenia</em>, also of constant width but commonly folded and twisted; and the lanceolate form <em>Lanceoforma</em>. Furthermore, we have reassessed the related fossil reports within a comprehensive database to evaluate their spatiotemporal distribution. The result shows that all three fossil genera exhibit long temporal ranges with the first appearances predating the Ediacaran. Given their simplistic and often indistinguishable morphology, <em>Vendotaenia</em> and related vendotaenids are deemed unsuitable for stratigraphic correlation of the uppermost Ediacaran.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":"427 ","pages":"Article 107882"},"PeriodicalIF":3.2,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Antarctic phytoplankton communities restructure under shifting sea-ice regimes","authors":"Alexander Hayward, Simon W. Wright, Dustin Carroll, Cliff S. Law, Pat Wongpan, Andrés Gutiérrez-Rodriguez, Matthew H. Pinkerton","doi":"10.1038/s41558-025-02379-x","DOIUrl":"https://doi.org/10.1038/s41558-025-02379-x","url":null,"abstract":"<p>Phytoplankton are critical to the Antarctic marine food web and associated biological carbon pump, yet long-term shifts in their community composition are poorly understood. Here, using a machine learning framework and combining pigment samples and environmental samples from austral summertime 1997–2023, we show declines in diatoms and increases in haptophytes and cryptophytes across much of Antarctica’s continental shelf. These trends—which are linked to sea ice increases—reversed after 2016, with a rebound in diatoms and a large increase in cryptophytes, coinciding with the loss of sea ice. Significant changes (<i>P</i> &lt; 0.05) across the 25-year dataset include diatom chlorophyll <i>a</i> (chl-<i>a</i>) declines of 0.32 mg chl-<i>a</i> m⁻³ (~33% of the climatology) and increases for haptophytes and cryptophytes of 0.08 and 0.23 mg chl-<i>a</i> m⁻³, respectively. The long-term shifts in phytoplankton assemblages could reduce the dominance of the krill-centric food web and diminish the biologically mediated export of carbon to depth, with implications for the global-ocean carbon sink.</p>","PeriodicalId":18974,"journal":{"name":"Nature Climate Change","volume":"119 1","pages":""},"PeriodicalIF":30.7,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144701430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The GRE46 Epithermal Gold Deposit, Cowal, New South Wales: Geology, Mineralization, Alteration, and Ore Genesis","authors":"Markus Staubmann, David R. Cooke, Scott Halley, Tilen Milojkovic, Ben Reid, Matthew Green, Ned Howard, Mathew Clifford","doi":"10.5382/econgeo.5160","DOIUrl":"https://doi.org/10.5382/econgeo.5160","url":null,"abstract":"The 2.74 Moz structurally controlled epithermal GRE46 gold deposit is located on the western margin of the Cowal Igneous Complex in central New South Wales, Australia. At the regional scale, the Cowal Igneous Complex is located toward the southern end of the poorly exposed Junee-Narromine volcanic belt, the westernmost of four remnant volcanic belts that together constitute the Ordovician to early Silurian Macquarie arc. The GRE46 deposit is located at the northern end of a 4.5-km-long structural corridor that is defined by several prominent arc-parallel structures. This structural corridor also contains the E40, E41, and E42 gold deposits, and has a collective pre-mining gold endowment of over 14 Moz. The GRE46 deposit is hosted in a sequence of calc-alkalic to shoshonitic subaqueous volcanic and volcaniclastic rocks, interpreted to have formed in an intra-oceanic magmatic arc environment. The host stratigraphy is dominated by reworked volcanic deposits and nonvolcanic sedimentary deposits that include mud- to sandstones, pebble to cobble conglomerates and polymictic volcanic breccias and debris flows. Lesser primary volcanic rocks consist of coherent andesite to dacite flows with common hyaloclastite and peperite textures, and diorite to granodiorite dikes and sills. Gold mineralization at GRE46 occurs primarily in association with millimeter- to centimeter-scale quartz-carbonate-pyrite veins, with minor chalcopyrite, galena, sphalerite, and rare telluride minerals. Multiple styles of mineralized veins are present, including composite and banded dilatant veins, shear veins, stringer veins, and high-grade quartz-sulfide breccia veins. The host rocks were variably hydrothermally altered, with the style and intensity of alteration influenced by proximity to fluid-flow controlling structures and protolith compositions. The highest gold grades are closely associated with pervasive quartz + white mica + ankerite + pyrite alteration that overprinted chlorite + albite + calcite ± magnetite alteration. At the deposit scale, gold mineralization was strongly influenced by the pre-existing structural architecture, leading to heterogeneous hydrothermal fluid flow in zones of enhanced permeability that were created due to competency contrasts in the volcano-sedimentary stratigraphic package. GRE46 can be classified as an intrusion-related epithermal style of gold mineralization. The deposit has several characteristics, including the ore and gangue mineralogy, style and textures of associated veining, and the alteration assemblage, which are broadly consistent with both the intermediate sulfidation and the carbonate-base metal epithermal models.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"12 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144712271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights Into the Magma Source and Evolution of the Taca Taca Bajo Porphyry Deposit: Implications for the Metallogeny and Cu Fertility of the Central Andean Retro Arc","authors":"Madeleine A. Ince, Steffen G. Hagemann, Nora A. Rubinstein, Marco L. Fiorentini, Anthony I.S. Kemp, Christopher M. Fisher, Tim Ireland, Santiago Gigola","doi":"10.5382/econgeo.5169","DOIUrl":"https://doi.org/10.5382/econgeo.5169","url":null,"abstract":"The magmatic processes that lead to porphyry Cu ore formation in continental retro-arc environments are not well understood. As a result, the uncertainty of predictive exploration in these tectonic settings is elevated, and new case studies are needed to enhance the probability of success in target identification. The Taca Taca Bajo porphyry Cu-Mo-Au deposit is a well-mineralized (11.7 Mt contained Cu), retro-arc expression of the Middle Eocene to Early Oligocene metallogenic belt in the central Andes and represents a key location for investigating continental retro-arc magmatic processes that culminate in the formation of porphyry Cu deposits. Mineralization at Taca Taca Bajo is spatially and temporally correlated with a NE-SW–trending rhyodacitic porphyry dike swarm. Six samples of the mineralized Taca Taca Bajo rhyodacite porphyry and one of the barren west rhyodacite porphyry were analyzed for whole-rock geochemistry and zircon petrochronology (U-Pb geochronology, O isotopes, Lu-Hf isotopes, trace element geochemistry). The U-Pb SHRIMP analyses of zircons from the Taca Taca rhyodacite porphyry intrusions reveal ages ranging from 30.3 ± 0.5 Ma to 29.1 ± 0.3 Ma (95% confidence interval). The barren west rhyodacite porphyry sample yields an overlapping zircon crystallization age of 30.4 ± 0.4 Ma (U-Pb SHRIMP; 95% confidence interval) with mineralized samples. Whole-rock geochemistry reveals a subducted slab component to the magma, with enrichments in Ba and Th as well as a marked negative Nb and Ta anomaly. The mean zircon δ18O of both the barren and mineralized Oligocene intrusions ranges from 5.6 ± 0.5 to 5.8 ± 0.2‰ (2 standard deviations [SD]), and zircon εHf from 5.3 ± 2.4 to 7.6 ± 0.7 (2 SD). These similarities suggest that the mineralized and barren intrusions may have a relatively juvenile mantle-derived source with minor assimilation of older crust. Inherited zircons yield U-Pb ages of 48 to 1063 Ma, with a cluster at 230 to 280 Ma, indicative of interaction with older arc magmatic rocks of the lower Choiyoi Igneous Complex. The Taca Taca Oligocene intrusions are moderately hydrous (mean zircon Eu/Eu* = 0.25–0.34) and oxidized (mean ΔFMQ = 0.2–1.0 [FMQ = fayalite-magnetite-quartz]) as estimated from zircon-based proxies. However, they also have lower inferred H2O contents and fO2 than other Cu-porphyry deposits of the Eocene to Early Oligocene metallogenic belt (e.g., Escondida, Chuquicamata, El Salvador). Based on these data, it is possible to conclude that the Taca Taca Bajo deposit, despite being a large porphyry Cu deposit, may have failed to reach the scale of some others in the metallogenic belt because it experienced a relatively isolated, short (1–1.5 m.y.) magmatic pulse, and did not undergo the multimillion year build-up of magmatism characteristic of these major deposits.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"26 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144712299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}