Precambrian Research最新文献

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Titanite petrochronology, phase equilibria modelling and the role of amphibole during decompression: Insights from the Shabogamo Domain, central Grenville Province 榍石岩石年代学、相平衡模型和闪石在减压过程中的作用:格勒尼维尔省中部沙博加莫岩域的启示
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-09-14 DOI: 10.1016/j.precamres.2024.107571
{"title":"Titanite petrochronology, phase equilibria modelling and the role of amphibole during decompression: Insights from the Shabogamo Domain, central Grenville Province","authors":"","doi":"10.1016/j.precamres.2024.107571","DOIUrl":"10.1016/j.precamres.2024.107571","url":null,"abstract":"<div><p>In this contribution, we present new petrochronological results from samples collected the Shabogamo Domain, of the Grenville Province, Québec, Canada. The Shabogamo domain has a distinct geophysical signature and has been proposed to be linked with the well-studied allochthonous Manicouagan Imbricate Zone. We document a Pressure-Temperature-time (P-T-t) path for an amphibolite sample by combining several approaches including: i) an ordinary least square model able to estimate P-T conditions from amphibole composition using a previously semi-quantitative amphibole thermobarometer ii) titanite petrochronology; iii) phase equilibria modelling; iv) trace element thermometry. We show that single element thermobarometry on titanite and amphibole pairs yield the information necessary to reconstruct a decompression P-T path from peak P-T conditions of 1.8 GPa – 775 °C down to 1.2 GPa – 750 °C and are consistent with results of phase equilibria modelling. Titanite U-Pb geochronology results indicate growth between 987 ± 16 Ma and 969 ± 17 Ma. These results are consistent with U-Pb geochronology on zircon from a dyke that crosscuts the amphibolite and from a deformed leucosome sampled in the domain’s footwall. Zircon from the crosscutting dyke appear to have grown at 985 ± 18 Ma without interaction with garnet, whereas zircon from the deformed leucosomes grew at 972 ± 16 Ma during high-pressure metamorphism. Integrating the results of this study into the regional context outlines the exhumation of a second high-P allochthonous nappe, most likely by ductile extrusion, coeval with the burial of the parautochthonous footwall. This study further supports the growing body of evidence for a major tectonic event during the later phase of the Grenvillian Orogeny.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301926824002845/pdfft?md5=6e00525bbec50fafd2f17a638052236b&pid=1-s2.0-S0301926824002845-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142232740","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}
引用次数: 0
The presences of water in the generation of calc-alkaline I-type granitic magmas at continental arc: Insight from Neoproterozoic Ailaoshan magmatism at the southwestern margin of the Yangtze Block, South China 水在大陆弧钙碱性I型花岗岩岩浆生成过程中的存在:华南扬子地块西南缘新新生代爱罗山岩浆活动的启示
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-09-14 DOI: 10.1016/j.precamres.2024.107567
{"title":"The presences of water in the generation of calc-alkaline I-type granitic magmas at continental arc: Insight from Neoproterozoic Ailaoshan magmatism at the southwestern margin of the Yangtze Block, South China","authors":"","doi":"10.1016/j.precamres.2024.107567","DOIUrl":"10.1016/j.precamres.2024.107567","url":null,"abstract":"<div><p>Water is crucial in generating granitic systems; however, its role (i.e., dehydration, low to high water-fluxed melting) in granitic magmatism in continental arcs remains unsettled and poorly understood. Neoproterozoic arc-related igneous rocks are uncovered along the western margin of the Yangtze Block, presenting a complex compositional array ideal for deciphering the influence of water content within the continental arc and its geodynamic significance. The Jinping granites, in the Ailaoshan zone, are emplaced at 750 ± 4 Ma, as determined by zircon U-Pb dating. These medium to coarse-grained granites consist predominantly of plagioclase, quartz, K-feldspar, muscovite, and biotite. Characterized by high SiO<sub>2</sub> (71.2–73.5 wt%), alkalis (K<sub>2</sub>O+Na<sub>2</sub>O=7.54–9.56 wt%) and low Fe<sub>2</sub>O<sub>3</sub><sup>T</sup> (1.01–1.66 wt%), MgO (0.53–0.85 wt%), and CaO (0.15–0.93 wt%) concentrations, they exhibit high-K calc-alkaline signatures. The negative correlation between P<sub>2</sub>O<sub>5</sub> and SiO<sub>2</sub>, alongside the positive correlation between Rb and Y, typifies the Jinping granites as I-type granites. Low La/Nb (1.96–3.43) and Nb/Ta (8.57–11.3) ratios, but high Th/La (0.28–0.46) and Zr/Sm (30.5–47.7) ratios, as well as whole rock ε<sub>Nd(t)</sub> (−0.4 to +1.3) and zircon ε<sub>Hf(t)</sub> values (+5.25 to +8.53) of the studied granites are similar to synchronous mafic rocks at the western margin of the Yangtze Block. These features suggest partial melting origin from the mafic lower crust. Thermodynamic modeling posits that the Neoproterozoic Ailaoshan I-type granitic rocks may have formed through water-fluxed melting (2.0–3.5 wt% H<sub>2</sub>O) under medium pressure conditions (9 kbar). It is postulated that slab rollback could have prompted water (as hydrous melt or fluids) release from hydrous minerals in the underlying cumulate mafic rocks, subsequently triggering water-fluxed melting in the lower crust. In contrast, high water-fluxed melting-generated adakitic granites with low K<sub>2</sub>O/Na<sub>2</sub>O ratios (&lt;0.8) in the region, spatially and temporally associated with the Jinping granites, reflect higher water content in the deeper crust. This supports the notion that water was conveyed from depths to surface, facilitating the conversion of adakitic rocks into I-type granites as water content diminished. Thus, water content within the lower crust plays a pivotal role in the genesis of granitic rocks with varied compositions in a continental arc setting.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142232047","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}
引用次数: 0
Comment on: “Passive continental margin subducted to mantle depths: Coesite-bearing metasedimentary rocks from the neoproterozoic Brasília Orogen, west Gondwana margin” 评论"被动大陆边俯冲至地幔深处:来自冈瓦纳西部边缘新近纪巴西利亚造山带的含薏苡岩的变质岩"
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-09-05 DOI: 10.1016/j.precamres.2024.107558
{"title":"Comment on: “Passive continental margin subducted to mantle depths: Coesite-bearing metasedimentary rocks from the neoproterozoic Brasília Orogen, west Gondwana margin”","authors":"","doi":"10.1016/j.precamres.2024.107558","DOIUrl":"10.1016/j.precamres.2024.107558","url":null,"abstract":"","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142148039","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}
引用次数: 0
Climatic-hydrologic influence on redox condition in the Cryogenian interglacial Nanhua Basin: Insights from the Datangpo Formation in the northwestern Yangtze Block, South China 气候-水文对冰期南华盆地氧化还原条件的影响:华南西北部扬子地块大塘坡地层的启示
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-09-04 DOI: 10.1016/j.precamres.2024.107557
{"title":"Climatic-hydrologic influence on redox condition in the Cryogenian interglacial Nanhua Basin: Insights from the Datangpo Formation in the northwestern Yangtze Block, South China","authors":"","doi":"10.1016/j.precamres.2024.107557","DOIUrl":"10.1016/j.precamres.2024.107557","url":null,"abstract":"<div><p>Tracking climatic and oceanic redox changes throughout the Neoproterozoic Cryogenian is crucial to a better understanding of the coevolution of life and environment in geological history. However, the processes and driven mechanisms of redox evolution in the Cryogenian interglacial ocean still remain uncertain. Here, we present a combined study of geochemical proxies, such as paleoclimatic proxies (CIA and Zr/Al) and paleosalinity proxies (B/Ga and Sr/Ba), from the interglacial Datangpo Formation in the shallow-water Zuojiawan section exposed in the northwestern Yangtze Block, to constrain climatic and hydrologic changes on redox conditions. Our data indicate that two apparently climatic cycles from warming to cooling occurred during the deposition of the Datangpo Formation, supplementing the monotonous climatic warming in previous research during the Cryogenian interglaciation. The low B/Ga and Sr/Ba ratios throughout Datangpo Formation suggest a continuous freshwater condition, which is in contrast to a transition of marine condition to brackish condition in relatively deep-water sections. Compiled salinity reconstructions at different paleo-depths imply the salinity gradient in the Nanhua Basin with a density stratification like modern Baltic Sea, at least during the early Cryogenian interglacial period. We find that the climate-driven local riverine freshwater input may be a significant driver for maintaining long-term freshwater condition in the Zuojiawan section. Accompanied by synchronously climatic warming, the progressive desalinization with declining B/Ga and Sr/Ba ratios in the middle to upper deposition of the Datangpo Formation are probably attributed to the persistent freshwater input to a nearshore shallow-water paleogeographic setting. Combined the improving oceanic oxygenation backdrop with the elevating seawater sulfate concentration in the Nanhua Basin in this period, we conclude that the continuous dilution of seawater in the restrict (semi-) Nanhua Basin could attenuate the density stratification and enhance the vertical mixing of watermass, favoring the ventilation of deepwater and penetration of sulfate. This contribution provides a new insight for the study of salinity changes on redox conditions in the Yangtze Block during the Cryogenian interglacial period, and provides new data for supporting a systematic understanding of the evolutional mechanism of oceanic redox state.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142136644","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}
引用次数: 0
Growth of the Central Orogenic Belt, North China Craton through accretion of different Neoarchean arc terranes: Perspective from the Linshan complex 华北克拉通中央造山带在不同新元古代弧形陆相的增生过程中的成长:林山复合体的视角
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-08-31 DOI: 10.1016/j.precamres.2024.107555
{"title":"Growth of the Central Orogenic Belt, North China Craton through accretion of different Neoarchean arc terranes: Perspective from the Linshan complex","authors":"","doi":"10.1016/j.precamres.2024.107555","DOIUrl":"10.1016/j.precamres.2024.107555","url":null,"abstract":"<div><p>The onset of plate tectonics and crustal growth processes in the early Earth have been controversial scientific issues in the geoscience. The North China Craton (NCC) preserves widespread 3.8–2.5 Ga rocks, providing an ideal place to understand early continent formation and evolution. The Linshan complex located in the southern segment of the Central Orogenic Belt (COB) of the NCC, is mainly composed of TTG (tonalite-trondhjemite-granodiorite)-diorite gneisses and metamorphic volcanic-sedimentary units dominated by gabbro, basalt, basaltic andesite and biotite-plagioclase gneiss. Detailed mapping on the scale of 1:100 of a structural transect shows that the Linshan complex has mainly experienced two major deformation events including top-to-the-SE thrust faults and late NE-trending high-angle normal faults. Detailed zircon U-Pb dating shows that gabbro, basaltic andesite, and TTG gneiss mainly formed at ca. 2.52–2.50 Ga. Gabbros and basalts display enrichment of LREE and negative Nb and Ta anomalies, and basaltic andesites display mixed MORB-IAT geochemical affinities. Basalts and basaltic andesites are members of the Nb-enriched basalt series with high absolute Nb contents (&gt;6 ppm). TTG gneisses are geochemically divided into high-pressure and low-pressure TTGs. High-pressure TTGs are characterized by high ratios of La/Yb<sub>cn</sub> (26.29–45.73) and fall into the adakitic region in the La/Yb<sub>cn</sub>-Yb<sub>cn</sub> diagram. Considering the close contact with Nb-enriched basaltic series, it is proposed that high-pressure TTGs may have formed by partial melting of a subducting oceanic slab with garnet and amphibole and/or rutile as residues. Low-pressure TTGs are characterized by low ratios of La/Yb<sub>cn</sub> and Sr/Y with marked negative Eu anomalies, indicating partial melting at shallow crustal levels. Regional tectonic relations have defined the Neoarchean Dengfeng island arc-forearc accretionary complex to the east of the Linshan complex. Thus, we propose that the gabbros-basalts-basaltic andesites in the Linshan complex mostly formed in a Neoarchean suprasubduction back-arc basin by rifting of a TTG-dominated island arc terrane. The final closure of the back-arc basin resulted in their tectonic juxtaposition forming thrust-imbricated structures. There may have been several Neoarchean “forearc-island-arc-backarc” systems in the NCC that are similar to modern accretionary tectonic orogens, indicating that plate tectonics has been in operation since at least 2.55–2.50 Ga.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142098069","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}
引用次数: 0
1.38 Ga magmatism and the extension tectonics in East Kunlun, northern Tibetan Plateau 青藏高原北部东昆仑1.38 Ga岩浆活动与延伸构造
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-08-28 DOI: 10.1016/j.precamres.2024.107551
{"title":"1.38 Ga magmatism and the extension tectonics in East Kunlun, northern Tibetan Plateau","authors":"","doi":"10.1016/j.precamres.2024.107551","DOIUrl":"10.1016/j.precamres.2024.107551","url":null,"abstract":"<div><p>Numerous Paleo- to Mesoproterozoic magmatic rocks were emplaced during the assembly, accretion and break-up of the Columbia supercontinent, and are keys to illustrating the supercontinent circle. The geological, petrological, geochronological and geochemical data of the newly discovered <em>meta</em>-felsic and <em>meta</em>-mafic magmatic rocks from the Wulonggou area are presented in this study to shed light on the Mesoproterozoic geodynamic setting of the Central Kunlun Belt and the Qaidam Block. Zircon U-Pb geochronological results indicate that the crystallization ages of the <em>meta</em>-felsic samples are 1385–1376 Ma, and the <em>meta</em>-mafic is 1379 ± 25 Ma (MSWD=0.17). Samples from the <em>meta</em>-felsic unit have SiO<sub>2</sub> contents of 68.37–73.03 wt% and belong to the high-K calc-alkaline series. They exhibit similar REE distribution patterns and display enrichment in light rare earth elements (LREES) and negative Eu anomalies. Enrichments in Rb, Ba, Th, U and K, depletion in Nb, Ta, Sr, P and Ti are seen in the primitive mantle-normalized trace element pattern diagram. Magmatic zircons from different <em>meta</em>-felsic samples yield variable <em>ε</em><sub>Hf</sub>(<em>t</em>) values of −8.14 to + 9.37 corresponding to ca. 1.7–2.0 Ga two-stage Hf model ages. Samples from the <em>meta</em>-mafic unit have low SiO<sub>2</sub> concentrations of 49.87–50.43 wt%, high contents of Fe<sub>2</sub>O<sub>3</sub><sup>T</sup>, MgO, CaO and TiO<sub>2</sub>, and Mg# values of 52–58. They show low total REE concentrations of 19.8–30.4 µg/g, and depletion in LREES, flat HREES distribution patterns with (La/Yb)<sub>N</sub> of 0.27–0.53 and insignificant Eu anomalies. Flat distribution pattern of high field strength elements (HFSEs) is observed in the primitive mantle-normalized trace element pattern diagram. They display similar immobile elements’ concentrations and distribution patterns, low Ti/Y, Nb/Y, La/Yb, and high Nb/La ratios, comparable with the present-day normal middle ocean ridge basalt. Zircons from the <em>meta</em>-mafic sample have mostly positive <em>ε</em><sub>Hf</sub>(<em>t</em>) values ranging from −0.10 to + 4.10 with a single stage Hf model ages of ca. 1.7–2.0 Ga. The geochemical result implies that the <em>meta</em>-felsic unit was generated by partial melting of the Paleoproterozoic juvenile mafic lower-crustal material with mantle attributions, and the <em>meta</em>-mafic unit was probably from partial melting of the lithospheric mantle. Synthesizing the above evidences, Wulonggou Mesoproterozoic <em>meta</em>-magmatic rocks are a bimodal suite formed in a continental extensional tectonic setting which is probably related to the break-up of the Columbia supercontinent.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142089669","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}
引用次数: 0
Pressure–temperature evolution, protolith characteristics and tectonic setting of granulite facies rocks from Laojinchang area in the Longgang Block, China 中国龙岗区块老金厂地区花岗岩面岩石的压力-温度演化、原岩特征和构造背景
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-08-27 DOI: 10.1016/j.precamres.2024.107552
{"title":"Pressure–temperature evolution, protolith characteristics and tectonic setting of granulite facies rocks from Laojinchang area in the Longgang Block, China","authors":"","doi":"10.1016/j.precamres.2024.107552","DOIUrl":"10.1016/j.precamres.2024.107552","url":null,"abstract":"<div><p>The Archean supracrustal rock series in the Laojinchang area of Jilin Province, China provide valuable insights into the Precambrian geological evolution of the North China Craton. This study presents new results on petrography, geochemistry, mineralogy, isotope geochronology and phase equilibrium modeling of the Laojinchang granulite facies metamorphic rocks. The protolith ages of garnet two-pyroxene granulite and amphibolite from Sidaolazihe Formation, and two-pyroxene granulite from Laoniugou Formation are 2565 ± 5.9 Ma, 2512 ± 17 Ma, and 2509.2 ± 8.6 Ma, respectively, with the metamorphic age recorded by amphibolite being 2475.6 ± 9 Ma. New geochemical data indicates that TTGs (tonalite-trondhjemite-granodiorite) weathering in an island arc environment formed the protolith of argillaceous gneiss of Sidaolazihe Formation. Basaltic andesite, formed under an island arc environment, was the protolith of garnet two-pyroxene granulite of Sidaolazihe Formation; while calc-alkaline basalt was the protolith of amphibolite from the same formation and two-pyroxene granulite from Laoniugou Formation. All these Archean supracrustal rocks exposed in the Laojinchang area have recorded nearly isobaric cooling (IBC) anticlockwise P-T paths with distinct prograde, peak and post-peak stages. The peak P-T conditions reached granulite facies, suggesting a heat source from underplated magmas. A tectonic model involving an island-arc setting is proposed for the evolution of these Neoarchean supracrustal rocks in Laojinchang area.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142083362","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}
引用次数: 0
Stratigraphic-chemostratigraphic assessment of early dolomitization and associated phosphogenesis of the Ediacaran-Cambrian Salitre Formation, Irecê Basin, Brazil 巴西伊雷塞盆地埃迪卡拉-寒武纪萨利特尔地层早期白云石化及相关磷化作用的地层-化合地层评估
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-08-27 DOI: 10.1016/j.precamres.2024.107541
{"title":"Stratigraphic-chemostratigraphic assessment of early dolomitization and associated phosphogenesis of the Ediacaran-Cambrian Salitre Formation, Irecê Basin, Brazil","authors":"","doi":"10.1016/j.precamres.2024.107541","DOIUrl":"10.1016/j.precamres.2024.107541","url":null,"abstract":"<div><p>During the Precambrian − Cambrian transition, the occurrence of phosphogenesis and the rise in atmospheric oxygen levels are closely linked to the proliferation of life. However, the mechanisms associated with these phenomena and their underlying causes are not well understood. The Irecê Basin represents the remnants of intracratonic marine environments that document the Neoproterozoic sea flooding of West Gondwana. This study presents an integrated analysis of sedimentary facies and chemostratigraphy through high-resolution sampling of pristine limestones and dolomites from the Salitre Formation in east-central Brazil. The aim is to explore the relationship between environmental settings and phosphatized stromatolites by combining detailed facies descriptions with isotopic and geochemical data. A total of fifteen lithofacies types are identified and grouped into seven major facies associations. These associations reveal a depositional stacking pattern defined by flooding surfaces and transgressive–regressive cycles, allowing for the division of the Salitre Formation into two depositional sequences. The basal sequence includes sedimentary phosphorite deposits intimately associated with widespread dolomitization levels at the top. Here, we describe a combination of two major processes for the dolomitization model of the Salitre Formation, with a contribution of evaporative environment settings related to a sabkha, and the influence of a meteoric mixing zone. Furthermore, three stages of phosphogenesis have been identified, with two of them interpreted as early diagenetic deposition associated with stromatolites and early cementation, and the last one associated with a late stage of phosphogenesis. The combined analysis of REY patterns, <sup>87</sup>Sr/<sup>86</sup>Sr ratios, and geochemical results suggests a significant continental influence on both dolomitization and phosphogenesis. The identification of depositional settings and stratigraphic patterns for these deposits is crucial for the understanding of phosphogenesis during the Ediacaran, which may have been influenced by the continentalization of the marine environments forced by the intracratonic marine setting and the tectonic evolution at the end of the Neoproterozoic Era.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142083360","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}
引用次数: 0
SIMS U-Pb dating of baddeleyite-zircon pairs in mafic rocks to determine the ages of magmatic mineralization and hydrothermal remobilization in a Ni-Cu-(PGE) deposit 对岩浆岩中的巴德磊石-锆石对进行 SIMS U-Pb 测定,以确定一个镍-铜(PGE)矿床中岩浆成矿和热液再移动的年龄
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-08-27 DOI: 10.1016/j.precamres.2024.107556
{"title":"SIMS U-Pb dating of baddeleyite-zircon pairs in mafic rocks to determine the ages of magmatic mineralization and hydrothermal remobilization in a Ni-Cu-(PGE) deposit","authors":"","doi":"10.1016/j.precamres.2024.107556","DOIUrl":"10.1016/j.precamres.2024.107556","url":null,"abstract":"<div><p>Ni-Cu-(PGE) sulfide deposits associated with mafic–ultramafic rocks are the most important sources of Ni and platinum-group elements (PGE) in the world. These deposits also contain significant amounts of Cu. Such deposits are generally considered to have formed by multiple stages of primary magmatic concentration and secondary hydrothermal remobilization. However, constraining the ages of Ni-Cu-(PGE) sulfide deposits has proven challenging, particularly those that have experienced post-magmatic hydrothermal overprinting and remobilization. The lack of robust geochronology data has hindered understanding of the geological controls on this important type of mineralization. The Chibaisong Ni-Cu-(PGE) sulfide deposit in the North China Craton is characterized by disseminated and net-textured ores formed by magmatic processes and overprinted by hydrothermal Cu-rich vein stockwork. The Cu-rich vein stockwork is fracture-controlled, and contains a mineral assemblage of Ni-Cu sulfides (chalcopyrite, pyrrhotite, pentlandite), amphibole and quartz. Chalcopyrite in the hydrothermal stockwork is relatively depleted in Ni but enriched in Ag and Cd compared with disseminated magmatic chalcopyrite, typical of hydrothermal superimposed ores as documented elsewhere. We identified baddeleyite-zircon pairs associated with Ni-Cu sulfides in hydrothermal superimposed ores of the Chibaisong deposit, in which the baddeleyite is unequivocally of primary igneous origin whereas the zircon represents the replacement product of baddeleyite during hydrothermal alteration. <em>In situ</em> SIMS U-Pb dating of baddeleyite and zircon yielded weighted mean <sup>207</sup>Pb/<sup>206</sup>Pb ages of 2181 ± 21 Ma and 1892 ± 33 Ma, respectively, interpreted as the timing of magmatic mineralization and subsequent hydrothermal remobilization of the Ni-Cu-(PGE) deposit. Our results explain the large discrepancies in sulfide Re-Os ages previously obtained from this deposit. This study demonstrates that on the basis of detailed BSE imaging, <em>in situ</em> SIMS U-Pb dating of baddeleyite-zircon pairs can provide robust age constraints for both magmatic mineralization and hydrothermal remobilization of Ni-Cu-(PGE) sulfide deposits hosted in mafic–ultramafic intrusions, although further studies are needed to test whether the formation of such deposits commonly entails multiple stages of hydrothermal remobilization. Since baddeleyite or baddeleyite-zircon pairs are common accessory minerals in Ni-Cu-(PGE)-bearing mafic–ultramafic rocks, the dating approach employed in this study may be applicable to similar deposits elsewhere.</p></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142083361","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}
引用次数: 0
Comment on “Subsurface distribution of granites and greenstones in the paleoarchean east Pilbara terrane from 3-D gravity inversion” 关于 "从三维重力反演看古近纪东皮尔巴拉地层中花岗岩和绿岩的地下分布 "的评论
IF 3.2 2区 地球科学
Precambrian Research Pub Date : 2024-08-25 DOI: 10.1016/j.precamres.2024.107539
{"title":"Comment on “Subsurface distribution of granites and greenstones in the paleoarchean east Pilbara terrane from 3-D gravity inversion”","authors":"","doi":"10.1016/j.precamres.2024.107539","DOIUrl":"10.1016/j.precamres.2024.107539","url":null,"abstract":"","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142058167","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}
引用次数: 0
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