Lithos最新文献

{"title":"Sub-solidus evolution of plagioclase-hosted Fe-Ti oxide micro-inclusions from oceanic gabbros, Mid-Atlantic ridge (10–13°N)","authors":"Ge Bian ,&nbsp;Olga Ageeva ,&nbsp;Alexey Pertsev ,&nbsp;Andras Kovacs ,&nbsp;Gerlinde Habler ,&nbsp;Qianqian Lan ,&nbsp;Rafal E. Dunin-Borkowski ,&nbsp;Olga Zhilicheva ,&nbsp;Rainer Abart","doi":"10.1016/j.lithos.2025.108211","DOIUrl":"10.1016/j.lithos.2025.108211","url":null,"abstract":"<div><div>Iron‑titanium oxide minerals are highly reactive under changing <em>P-T-f</em>O₂ conditions, and their chemical compositions and phase relations are important petrogenetic indicators. In this study, we use optical-, scanning electron-, and scanning transmission electron microscopy to investigate the sub-solidus and hydrothermal evolution of plagioclase-hosted Fe<img>Ti oxide micro-inclusions from two types of oceanic gabbro dredged from the Mid-Atlantic Ridge at 10–13°N and exhibiting different types of hydrothermal alterations. Initially, the micro-inclusions formed as oriented, needle-shaped titanomagnetite, by precipitation from Fe- and Ti-bearing plagioclase. In most of the studied gabbros, such inclusions evolved into magnetite-ilmenite intergrowths by high-temperature oxidation above the Curie temperature of magnetite. Further evolution of the Fe<img>Ti oxide micro-inclusions occurred during hydrothermal alteration at temperatures below the Curie temperature. Under low-intensity hydrothermal alteration, the micro-inclusions underwent minor dissolution and recrystallization. In contrast, intensive hydrothermal alteration under relatively reducing conditions resulted in substantial recrystallization and formation of magnetite-ulvospinel micro-inclusions, which were subsequently transformed into fine-grained magnetite-ilmenite ± ulvospinel aggregates. The phase contents and the microstructures of the plagioclase-hosted Fe<img>Ti oxide micro-inclusions, formed during the sub-solidus and hydrothermal evolution, provide insights into their evolution during cooling under changing redox conditions. These features are crucial for interpreting paleomagnetic measurements of Fe-rich gabbros, which often feature plagioclase hosting Fe<img>Ti oxide micro-inclusions.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108211"},"PeriodicalIF":2.5,"publicationDate":"2025-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144767055","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":"Geochemistry of mantle peridotites and chromitites from Upper Cretaceous ophiolites in NW Türkiye: Insights into abyssal to forearc mantle settings","authors":"Evren Arslan ,&nbsp;Osman Parlak ,&nbsp;Chao Zhang ,&nbsp;Junpeng Wang ,&nbsp;Dongyang Lian ,&nbsp;Yong Xu ,&nbsp;Guohui Chen ,&nbsp;Alastair Robertson ,&nbsp;Jingsui Yang ,&nbsp;Xisheng Xu ,&nbsp;Jun Hong","doi":"10.1016/j.lithos.2025.108208","DOIUrl":"10.1016/j.lithos.2025.108208","url":null,"abstract":"<div><div>This paper presents new data on whole-rock and mineral chemistry, trace elements of clinopyroxene (Cpx) and chromite, along with detailed petrographic observations of mantle peridotites and chromitites from the NW Anatolian (Harmancık-Orhaneli, Bursa) ophiolites to better understand contrasting geochemical signatures and different stages of lithospheric evolution along the İzmir-Ankara-Erzincan Ocean (İAEO) in northern Türkiye. The mantle peridotites, characterized by abundant high-grade podiform chromitites in Harmancık and banded chromitites in Orhaneli, are particularly notable. The mantle rocks include depleted- lherzolites, Cpx-rich harzburgites, harzburgites, Cpx-poor harzburgites, and dunites. Compositional variations in the mantle peridotites from both Harmancık and Orhaneli reflect continuous evolution driven by melt depletion and metasomatic enrichment occurring in both mid-ocean ridge (MOR) and supra-subduction zone (SSZ) environments. Our modeling suggests that the depleted lherzolites and Cpx-rich harzburgites in the Harmancık area are residues of anhydrous MOR-type melting of a fertile mid-ocean ridge mantle (FMM), with partial melting degrees of approximately 12–17% and 15–22%, respectively. In contrast, the harzburgites, Cpx-poor harzburgites, and dunites in the Harmancık area represent residues after 20–25% partial melting of a depleted MORB-type mantle, which itself was a residue following around 22% partial melting of an FMM during subduction initiation in the Late Cretaceous. The mantle peridotites in the Orhaneli area are comparatively more depleted, comprising Cpx-rich harzburgites, harzburgites, and dunites. This is supported by highly depleted rare earth element (REE) contents, similar to SSZ-type peridotites, indicating residues after 20–35% partial melting of a depleted MORB-type mantle (DMM). Furthermore, the compositions of parental magmas, as well as the trace element contents of chromites from the high-Cr chromitites and associated dunites in both Harmancık and Orhaneli, suggest that they were generated from boninitic melts in a supra-subduction zone (SSZ) environment. All the data suggests that the peridotites with high-grade podiform chromitites in the Harmancık region form the deeper mantle levels, whereas the banded chromitites within extensive dunite bodies in the Orhaneli region suggests proximity to the Moho transition zone, derived from the İAE Ocean in Late Cretaceous.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108208"},"PeriodicalIF":2.5,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144878571","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":"Effect of anatexis on mineral thermometers used in ultrahigh-temperature metamorphism","authors":"Shaoji Yang ,&nbsp;Yanru Song ,&nbsp;Haijin Xu ,&nbsp;Fan Feng","doi":"10.1016/j.lithos.2025.108206","DOIUrl":"10.1016/j.lithos.2025.108206","url":null,"abstract":"<div><div>Ultrahigh-temperature (UHT) metamorphism is crucial for deciphering thermal and tectonic regimes of orogen and is frequently accompanied by anatexis. However, accurate estimation of UHT metamorphic temperatures remains challenging, particularly due to the ambiguous effects of anatexis on mineral thermometers. The Paleoproterozoic pelitic granulites in the Kongling terrane, which have experienced both UHT metamorphism and significant anatexis, provide an ideal window to investigate this issue. Through integrated petrological, geochronological, and geochemical analyses, we evaluate the impact of anatexis on four widely used thermometers: Zr-in-rutile, Ti-in-zircon, ternary feldspar, and Ti-in-garnet. Petrological evidence, including melt pseudomorph (quartz + plagioclase + biotite + rutile/ilmenite) and cuspate plagioclase grains, confirms anatexis. Monazite geochronology constrains the timing of anatectic melt cooling to ∼2.0 Ga. Our results demonstrate that Zr contents in rutile and Ti contents in zircon are significantly influenced by diffusion and re-equilibration, respectively, in anatectic melts/fluids. The two thermometers yielded temperatures ranges of 443–859 °C (Zr-in-rutile) and 600–700 °C (Ti-in-zircon, majority data). Ternary feldspar thermometer records both UHT conditions (930–990 °C) and retrograde cooling temperatures (580–770 °C), while Ti-in-garnet preserves robust UHT conditions (∼940 °C). This study offers new insights into the fidelity and limitations of the mineral thermometers for UHT studies, particularly regarding their susceptibility to anatectic processes, and highlights the necessity of integrating multiple methods to reconstruct UHT thermal histories.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108206"},"PeriodicalIF":2.5,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144757096","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":"Platinum-group element geochemistry of the Heigutian FeTi oxide-bearing layered intrusion, Emeishan large igneous province, SW China","authors":"Yu-Wei She ,&nbsp;Lie-Meng Chen ,&nbsp;Song-Yue Yu ,&nbsp;Jun-Nian Yi ,&nbsp;Hai-Long He","doi":"10.1016/j.lithos.2025.108209","DOIUrl":"10.1016/j.lithos.2025.108209","url":null,"abstract":"<div><div>The nature (e.g., whether or not depleted in platinum-group elements) and sulfide segregation history of the parental magmas of layered mafic-ultramafic intrusions in the Emeishan Large Igneous Province (ELIP), SW China, remain controversial, which limits our understanding of their mineralization potential and exploration of platinum-group elements (PGE). To address these issues, we investigate the PGE geochemistry of the Heigutian layered mafic-ultramafic intrusion, a representative Fe<img>Ti oxide-bearing intrusion located in the central part of the ELIP. It comprises two distinct petrographic zones separated by a sharp contact. The lower zone is composed of olivine clinopyroxenite, magnetite gabbro, and medium-grained gabbro, while the upper zone consists of fine-grained gabbro. The olivine clinopyroxenite in the lower zone has a total PGE content of 28.8–31.7 ppb; the magnetite gabbro and medium-grained gabbro show much lower total PGE levels of 0.88–1.48 ppb and 0.09–0.18 ppb, respectively. The fine-grained gabbro in the upper zone exhibits a broader total PGE range of 2.01–32.27 ppb. The decoupling between Ru and Ir in the fine-grained gabbro, together with the negative Ru anomaly, suggests that the parental magma of the fine-grained gabbro did not undergo early-stage sulfide segregation but experienced significant removal of RuS₂ before emplacement. Given the mantle-normalized patterns of PGE analogous to those of the Emeishan PGE-undepleted high-Ti basalts and mantle-like Cu/Pd ratios (4 × 10³ to 7 × 10⁴) in the fine-grained gabbro, it can be inferred that the parental magmas were undepleted in PGE. The positive correlations between PGE and TiO_2, Ni, and Cr indicate in-situ sulfide immiscibility driven by fractional crystallization of olivine and Fe<img>Ti oxides during the formation of the lower zone. This sulfide immiscibility could potentially contribute to PGE mineralization in the lower part of the intrusion. Given the similarities in PGE features between the Heigutian intrusion and other layered mafic-ultramafic intrusions, there is substantial potential for exploring PGE mineralization within coeval Fe<img>Ti oxide-bearing layered intrusions in the ELIP.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108209"},"PeriodicalIF":2.5,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144767054","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":"Wide distribution of 3.46–3.1 Ga rocks in the Kongling Complex of the Huangling area, Yangtze Craton, south China: Petrogenesis and significance","authors":"Chunyan Dong ,&nbsp;Yunxu Wei ,&nbsp;Simon A. Wilde ,&nbsp;Hangqiang Xie ,&nbsp;Xin Deng ,&nbsp;Guangfu Xing ,&nbsp;Dunyi Liu ,&nbsp;Yusheng Wan","doi":"10.1016/j.lithos.2025.108203","DOIUrl":"10.1016/j.lithos.2025.108203","url":null,"abstract":"<div><div>The early evolution of the Earth is one of the most fundamental issues in Earth science. Here, we present whole-rock geochemistry, SHRIMP U<img>Pb zircon dating, and Hf isotopic analysis of newly-discovered Paleoarchean-Mesoarchean rocks in the Kongling Complex of the Huangling area at the northern margin of the Yangtze Craton, south China. Paleoarchean (3.46 Ga) supracrustal rocks (biotite-plagioclase gneisses) have been identified for the first time, with the rocks having low ΣREE (total REE) contents of 65.9 ppm, a low (La/Yb)_n value of 6.4, and magmatic zircons with ε_Hf(t) values from −6.22 to −1.31 and t_DM2(Hf) model ages of 4.11–3.82 Ga. Trondhjemitic gneisses with zircon ages of 3.3–3.1 Ga were identified in four areas, and xenocrystic zircons of similar age occur in widespread 3.0–2.9 Ga trondhjemitic gneisses. All the trondhjemitic gneisses are similar in major elements but show large variations in trace element compositions, with ΣREE, (La/Yb)_n and Eu/Eu* being 17.87–295.04 ppm, 14.22–80.50 and 0.55–5.22, respectively. They contain magmatic zircons with ε_Hf(t) values from −5.06 to −0.35 and t_DM2(Hf) model ages of 3.91–3.56 Ga. They plot in the low-K mafic rock and tonalite fields in the Al₂O₃/(FeOt+MgO)–3CaO–5(K₂O/Na₂O) diagram. It is concluded that the Paleoarchean-Mesoarchean trondhjemitic rocks were formed either by partial melting of basaltic rocks under low- to medium-pressure conditions or by partial melting of earlier TTG rocks that formed under these conditions. The Kongling Complex formed the continental nucleus to the Yangtze Craton, with most crustal materials being derived from the mantle at pre-3.6 Ga.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108203"},"PeriodicalIF":2.5,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144781688","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":"Felsic trans-porphyry deposits and associated ore (Sn, Ta, Nb, pegmatites) viewed from physics, chemistry (cDFT) and geologic contexts","authors":"Jean-Louis Vigneresse ,&nbsp;Arpita Poddar ,&nbsp;Pratim Kumar Chattaraj","doi":"10.1016/j.lithos.2025.108200","DOIUrl":"10.1016/j.lithos.2025.108200","url":null,"abstract":"<div><div>Some base metals (Cu, Mo, W, Sn) are extracted from silicate melts at the magmatic stage in porphyry deposits. Metal grade increases from some ppb or ppm up to percent levels. The common case is the porphyry type (Cu, Mo) above subduction zones. We introduce the trans-porphyry type deposits (Sn) within continental plates, resulting from large-scale shearing between cratons. The global process for ore generation has a three-fold effect, from magma generation, emplacement, and formation of a immiscible phase (MIP). Metals first segregate from the crust during melting slightly above 800 °C. During magma ascent, the MIP remains above the critical point (731 °C), and chemically attracts metals, transporting them faster than the melt. Metals segregation from the melt occurs in a subcritical state. It relies on the chemical potential contrast (chemical partitioning), enhanced by their differential motion (viscosity, density). Chemical diffusion negatively competes with advection, yielding enrichment. With cooling, the melt splits into two phases, silicate-rich and aqueous-dominated, both are immiscible with the melt and the matrix. Metals diffusivity, melt and matrix viscosity, cap rock permeability, and the amount of fluids are investigated in a parametric formulation. It rules out a gentle chemical differentiation though diffusion. Metals segregation (Sn, Nb, Ta) into pegmatite and greisen are the ultimate products of ore formation. Models based on the bulk composition of rocks (granite, pegmatites, greisens) reveal inadequate since they do not incorporate fluids in enough quantity. The physical parameters are also bracketed by the chemical descriptors (chemical potential, hardness) that rule melt and matrix evolution. The combined investigation of the physical context and chemical attractivity provides new insights into such ore formation in a magmatic context. 275 w.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108200"},"PeriodicalIF":2.5,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144781690","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":"Distinct P–T evolution of Pan-African HT–LP metamorphism recorded by paragneisses from the Larsemann Hills, East Antarctica, and tectonic implications: Phase equilibria and geochronological constraints","authors":"Jinrui Zhang ,&nbsp;Xuanlong Shan ,&nbsp;Nan Zhang ,&nbsp;Pavel Talalay ,&nbsp;Chunjing Wei ,&nbsp;Yidan Wang ,&nbsp;Shuang Tang ,&nbsp;Yuan Li","doi":"10.1016/j.lithos.2025.108202","DOIUrl":"10.1016/j.lithos.2025.108202","url":null,"abstract":"<div><div>Different types of paragneisses are exposed in the Larsemann Hills and adjacent region, East Antarctica. We conducted a detailed study of a sillimanite–cordierite–biotite gneiss (sample AZSZ-08) and garnet–sillimanite–biotite gneiss (sample AZSZ-09), based on petrographic observations, phase equilibria modelling, and geochronology. Both samples preserve typical high-temperature and low-pressure (HT–LP) mineral assemblages, but record different clockwise <em>P–T</em> paths, including near-isobaric heating in sample AZSZ-08, and cooling and decompression in sample AZSZ-09. The peak <em>P–T</em> conditions were 4–5 kbar/780–800 °C and ∼ 11 kbar/∼900 °C, respectively. U<img>Pb dating of zircon, monazite, and rutile in sample AZSZ-08 yielded ages concentrated in three clusters at 2697–2568, 2496–2384, and 1003–822 Ma, and a definitive metamorphic age of ca. 535 Ma. Mica Rb<img>Sr dating of this sample yielded a cooling age of ca. 445 Ma. Zircon U<img>Pb dating of sample AZSZ-09 yielded detrital zircon ages concentrated at 1164–599 Ma, peak metamorphic ages of 560–540 Ma, and cooling ages of <em>ca</em>. 516 and 496–456 Ma. The detrital zircon age population indicates that sample AZSZ-08 was likely derived from Precambrian terranes located near the Larsemann Hills, while sample AZSZ-09 is similar to previously reported samples and has a Grenvillian protolith age. The metamorphic <em>P–T</em> paths and age data record Pan-African tectonothermal events that lasted for a relatively long period of time (560–450 Ma). Combined with a previous petrological study of the Prydz Belt, including determination of <em>P–T</em> paths and age data, the distinct <em>P–T</em> evolution of the HP–LP metamorphism may record processes at different crustal levels during uplift and subsequent extension in the Pan-African Orogeny.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108202"},"PeriodicalIF":2.5,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144721871","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":"Large-scale rare metal pegmatite formation via tectonic-induced pulsed injection of fractionated felsic magma in the Mufushan granite–pegmatite system, South China","authors":"Hao-Xiang Zhang ,&nbsp;Shao-Yong Jiang ,&nbsp;Wei Zhang ,&nbsp;Hui-Min Su","doi":"10.1016/j.lithos.2025.108189","DOIUrl":"10.1016/j.lithos.2025.108189","url":null,"abstract":"<div><div>The evolving understanding of magma reservoirs has challenged traditional models of pegmatite formation. The mechanisms by which granitic crystal mush is remobilized to extract pegmatitic melt remain enigmatic. Here, an integrated petrological study of the Cretaceous Mufushan batholith—focusing on two-mica monzogranite, muscovite monzogranite, barren pegmatites, and rare metal pegmatites—reveals distinct associations: (1) co-occurrence of NYF and LCT pegmatites spatially linked to two-mica monzogranite in the Duanfengshan region, and (2) barren pegmatite crusts and dikes associated with muscovite monzogranite in the Guanyuan region. Based on combined Sm-Nd isotopic and mica geochemistry data, we propose a tectonically driven melt extraction model in which crystal mush is remobilized by tectonic activity. Faults and fissures generated by tectonic activities generate the pressure gradients to remobilize overcooled granitic crystal mush, facilitating the extraction of granitic melt. The high degree of overcooling conditions results in the formation of pegmatitic textures. Melt migration along faults and fissures promotes fractional crystallization, concentrating rare metals to form mineralized pegmatites. This multiphase melt extraction initiated chemical fractionation within pegmatites. The muscovite monzogranite and its associated pegmatite crusts/dikes represent the final products of the Mufushan magma reservoir, which interacted with exsolved magmatic volatile phases. Our findings highlight the critical role of tectonically controlled remobilization of crystal mush in both the generation and extraction of pegmatite melts.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108189"},"PeriodicalIF":2.5,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144757098","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":"The state and fate of noble metals in bornite and digenite","authors":"Samuel A. King ,&nbsp;Cristiana L. Ciobanu ,&nbsp;Nigel J. Cook ,&nbsp;Ashley D. Slattery ,&nbsp;Sarah E. Gilbert ,&nbsp;J. Richard Kyle ,&nbsp;Kathy Ehrig ,&nbsp;Jie Yao","doi":"10.1016/j.lithos.2025.108198","DOIUrl":"10.1016/j.lithos.2025.108198","url":null,"abstract":"<div><div>The role of bornite and digenite as carriers of noble metals (Au, Ag, Pd) is assessed based on study of skarn ores from the Ertsberg East Skarn System, Ertsberg-Grasberg district, Papua, Indonesia. Characterisation of petrography, mineralogy, and geochemistry at the micron- and nanoscale answer the long-standing question of whether noble metals occur in solid solution in Cu-(Fe)-sulphides, or as nanoparticles (NPs), and how these distributions change as the ore cools. Endo- and exoskarn Cu<img>Au ores display a wide range of lamellar bornite-digenite intergrowths that are heterogeneous in high-magnification images. These intergrowths are interpreted to form by coarsening of nanoscale basket-weave textures composed of four species: bornite 2<em>a</em>, digenite 1<em>a</em>, anilite, and a phase we interpret as a variety of rhombohedral digenite. Monoclinic chalcocite is not present. These basket-weave textures are considered to result from bornite-digenite solid solutions in the system Cu-Fe-S. The diverse range of subtly different bornite-digenite intergrowth types, grain sizes, and morphologies are attributed to multiple generations of precipitates from bornite-digenite solid solution. Various Au-Ag-Pb-Te-(Se) phases and merenskyite occur as (sub)-micron inclusions throughout the lamellar intergrowths, indicating that the bornite-digenite precipitates are significant carriers of noble metals and accompanying elements. Bornite from forsterite skarn contains tens of ppm Au measured by LA-ICP-MS. Nanoscale imaging reveals the presence of Au-Ag-Te nanoparticles. Lattice-bound Au is estimated at &lt;10 ppm; the reworking of lamellar bornite-digenite intergrowths assists formation of nanoparticles and even micron-sized gold from initially lattice-bound Au and Ag. The nucleation of NPs containing Au, Ag, and Te alongside Cu, but not S, appears to be promoted during transformation of parent digenite 1<em>a</em> into lower temperature polymorphs. Among these phases is an enigmatic Cu₂Te phase, which may be a catalyst for precious metal enrichment in bornite-digenite ores. Merenskyite is also intergrown with the Cu₂Te phase, and contains trace Au, further emphasising the role of bornite-digenite solid solutions in scavenging noble metals from fluids in deposits like skarns formed at relatively high temperatures. The new evidence underpins a new model of noble metal entrapment via Cu<img>Te melts formed during phase transition in Cu-Fe-sulphide minerals with wide application in ore petrology.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108198"},"PeriodicalIF":2.5,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144721870","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":"Crystal-melt separation and mush rejuvenation in the Sanbaishan volcanic system, Southeast China: Evidence from geochemistry and Sr-Nd-Hf-Ba isotopes","authors":"Ming-Yao Zuo ,&nbsp;Kui-Dong Zhao ,&nbsp;Qian Li ,&nbsp;Zhi-Yong Zhu ,&nbsp;Wei Chen ,&nbsp;Shao-Yong Jiang","doi":"10.1016/j.lithos.2025.108196","DOIUrl":"10.1016/j.lithos.2025.108196","url":null,"abstract":"<div><div>The precise identification and understanding of crystal-melt segregation and mush rejuvenation have long been central themes in volcanological research. The Sanbaishan tuff (ST) in Southeast China consists of high-silica rhyolite (HSR; ∼20 vol% phenocrysts, &gt;70 wt% SiO₂) and crystal-rich trachyte (CRT; ∼40 vol% phenocrysts, &lt;67 wt% SiO₂). These two lithologies exhibit complementary compositional variations and distinct compositional gaps. LA-ICP-MS zircon dating reveals that the ST formed at 138–140 Ma, and both the HSR and the CRT share nearly identical Sr-Nd-Hf isotopic compositions (ε_Nd(t) = −8.1 to −7.7; (⁸⁷Sr/⁸⁶Sr)_<em>i</em> = 0.71133 to 0.71411; ε_Hf(t) = −11.3 to −7.0), indicating that the magma originated from the same shallow crustal mush reservoir. Zircon saturation thermometry and rhyolite-MELTS simulations suggest that the high-silica melts were extracted from a crystal-rich cumulate mush at depths of 13–14 km (340–420 MPa) under temperatures of 800–900 °C. Subsequently, the residual crystal cumulates underwent reheating, partial dissolution, and eventual rejuvenation. This evolutionary history is recorded in the disparities between the HSR and the CRT in terms of elemental compositions of phenocrysts and matrix, crystal-fraction differences, and temperature conditions. The HSR has slightly heavier Ba isotopic compositions (δ^138/134Ba = 0.01 to 0.03 ‰) compared to the CRT (δ^138/134Ba = −0.04 to −0.01 ‰), further reinforcing the interpretation that the HSR represents melt extracted from the crystal mush, whereas the CRT corresponds to eruptive material derived from the cumulates. The Sr-Nd-Hf isotopic homogeneity and the absence of mafic microgranular enclaves suggest that the recharge magma primarily supplied heat and volatile components. Our findings suggest that mush rejuvenation likely played a crucial role in triggering the eruption of crystal-rich volcanic rocks.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108196"},"PeriodicalIF":2.5,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144722973","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}