Oxygen Isotopes of Iron Oxides as a Diagnostic Tool for Iron Formation-Hosted High-Grade Magnetite-Hematite Deposits

Research Article| May 01, 2004 THE ORIGIN OF HEMATITE IN HIGH-GRADE IRON ORES BASED ON INFRARED MICROSCOPY AND FLUID INCLUSION STUDIES: THE EXAMPLE OF THE CONCEIÇÃO MINE, QUADRILÁTERO FERRÍFERO, BRAZIL Carlos Alberto Rosière; Carlos Alberto Rosière Instituto de Geociências, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte MG, Brazil †Corresponding author: email, crosiere@dedalus.lcc.ufmg.br Search for other works by this author on: GSW Google Scholar Francisco Javier Rios Francisco Javier Rios Fluid Inclusion and Metallogenic Laboratory (EC1), Centro de Desenvolvimento da Tecnologia Nuclear (CDTN-CNEN), Cx. Postal 941, 30123-970 Belo Horizonte MG, Brazil Search for other works by this author on: GSW Google Scholar Author and Article Information Carlos Alberto Rosière Instituto de Geociências, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte MG, Brazil Francisco Javier Rios Fluid Inclusion and Metallogenic Laboratory (EC1), Centro de Desenvolvimento da Tecnologia Nuclear (CDTN-CNEN), Cx. Postal 941, 30123-970 Belo Horizonte MG, Brazil †Corresponding author: email, crosiere@dedalus.lcc.ufmg.br Publisher: Society of Economic Geologists Received: 20 Nov 2001 Accepted: 16 Dec 2003 First Online: 02 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 Economic Geology Economic Geology (2004) 99 (3): 611–624. https://doi.org/10.2113/gsecongeo.99.3.611 Article history Received: 20 Nov 2001 Accepted: 16 Dec 2003 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Carlos Alberto Rosière, Francisco Javier Rios; THE ORIGIN OF HEMATITE IN HIGH-GRADE IRON ORES BASED ON INFRARED MICROSCOPY AND FLUID INCLUSION STUDIES: THE EXAMPLE OF THE CONCEIÇÃO MINE, QUADRILÁTERO FERRÍFERO, BRAZIL. Economic Geology 2004;; 99 (3): 611–624. doi: https://doi.org/10.2113/gsecongeo.99.3.611 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract Petrographic and textural analysis combined with fluid inclusion studies by infrared microscopy of high-grade (>65% Fe) hematite ore samples from the Conceição deposit, in the northeastern part of the Quadrilátero Ferrífero, Brazil, indicate a complex process of oxidation and mineralization during two orogenic events, each developed under different conditions and involving distinct fluids. The earliest mineralization formed massive magnetite-rich orebodies under relatively reducing conditions in the early stages of the Transamazonian orogeny. Magnetite was oxidized (martitized) with the development of porous hematite crystals (hematite I). Possibly during this stage, new hematite crystals were also formed from low-temperature, low- to medium-salinity fluids, as indicated by two-phase fluid inclusions. The origin of these fluids is still uncertain but tentatively interpreted as being modified surface water. The fluids were transported along normal faults and fractures during post-tectonic collapse following the Transamazonian orogeny (2.1–2.0 Ga) and creation of the dome-and-keel structural pattern of the Quadrilátero Ferrífero. These solutions were also likely responsible for the initial oxidation of the iron formations and the development of hematite I. Subsequent uplifted hot basement rocks or post-tectonic plutons were probable heat sources for the regional metamorphism and development of a granoblastic fabric of hematite II grains in the iron formations and high-grade orebodies. However, the ore was only partially recrystallized, as several relics of the early magnetite, martite, and hematite are still preserved in the granular hematite II crystals. During the Brasiliano-Pan-African orogeny (0.8–0.6 Ga), high-salinity fluids, with temperatures varying from ~120° to a maximum of approximately 350°C, penetrated the iron formations along shear zones, crystallizing initially tabular and thereafter platy hematite crystals (hematite III and specularite) forming schistose orebodies. Quartz veins that cut across the ore and envelop specularite plates and ore fragments formed from late-stage, high-temperature, and low-salinity fluids containing CO2. These later fluids did not alter the ore.Each of these stages of mineralization produced orebodies with distinct features. Recurrent hydrothermal mineralization is thought to have been responsible for the development of giant, high-grade iron ore deposits in structurally favorable sites. Fold hinges with enhanced permeability and deep faults able to conduct the fluids to the surface, repeatedly over time, should be important targets for exploration of new resources. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Hetai goldfield is one of the largest gold mining districts in the South China Block. A complex paragenesis consists of three mineralization stages: syntectonic metamorphic stage, hydrothermal stage, and supergene stage. The syntectonic metamorphic stage is characterized by banded quartz (Q1) and invisible Au in mylonites. The hydrothermal stage, which is the main gold mineralization stage, can be divided into three substages: an early substage characterized by coarse‐grained quartz (Q2) + pyrite + arsenopyrite + pyrrhotite, an intermediate substage characterized by gray fine‐grained quartz (Q3) + electrum + poly‐sulphides + sericite + chlorite and a late substage with predominate white quartz (Q4) + calcite as well as lesser sulphides. During the supergene stage, malachite, covellite, and limonite were formed. Four types of fluid inclusions (FIs) in these types of quartz were identified: aqueous FIs (type 1), CO2‐bearing aqueous FIs (type 2), CO2‐rich FIs (type 3), and solid‐bearing FIs (type 4). Q1 only contains type 1 FIs; Q2 contains types 2 and 4 FIs; Q3 contains types 2 and 3 FIs; and Q4 only contains type 1 FIs. Microthermometric results show that the homogenization temperatures of fluid inclusions range from 350°C to 400°C for Q1, 250°C to 320°C for Q2, 138°C to 245°C for Q3, and 110°C to 207°C for Q4. Salinities of fluid inclusions range from 3.4 to 5.7 wt.%, 2.6 to 12.9 wt.%, 0.5 to 11.5 wt.%, and 0.2 to 7.3 wt.% for Q1, Q2, Q3, and Q4, respectively. Alteration minerals (sericite and chlorite) from the main mineralization stage have δDH2O‐VSMOW values of −62‰ to −98‰ and calculated δ18OH2O‐VSMOW values of 6.3‰ to 4.4‰. The in situ sulphur isotope analysis of pyrite yields a narrow δ34SCDTrange of −1.5‰ to −5.2‰ (average −3.4‰), combined with the Pb isotopic compositions of the sulphides, wall rocks, and Wucun pluton, revealing that the ore‐forming material was mainly derived from magmatic source. The mineralization age (sericite40Ar/39Ar: 159.3 ± 0.8 Ma) is close to the emplacement age of Wucun biotite monzonitic granite pluton (LA‐ICP‐MS zircon U–Pb age: 158.1 ± 1.9 Ma). These geochemical and geochronological data suggest that the main phase of gold mineralization in the Hetai goldfield is genetically related to the granitic activities in the Late Jurassic rather than the mylonitization event in the Late Triassic to Early Jurassic.

<strong class="journal-contentHeaderColor">Abstract.</strong> The incorporation of water isotopologues into the hydrology of general circulation models (GCMs) facilitates the comparison between modeled and measured proxy data in paleoclimate archives. However, the variability and drivers of measured and modeled water isotopologues, as well as the diversity of their representation in different models, are not well constrained. Improving our understanding of this variability in past and present climates will help to better constrain future climate change projections and decrease their range of uncertainty. Speleothems are a precisely datable terrestrial paleoclimate archives and provide well-preserved (semi-)continuous multivariate isotope time series in the lower latitudes and mid-latitudes and are therefore well suited to assess climate and isotope variability on decadal and longer timescales. However, the relationships of speleothem oxygen and carbon isotopes to climate variables are influenced by site-specific parameters, and their comparison to GCMs is not always straightforward. Here we compare speleothem oxygen and carbon isotopic signatures from the Speleothem Isotopes Synthesis and Analysis database version 2 (SISALv2) to the output of five different water-isotope-enabled GCMs (ECHAM5-wiso, GISS-E2-R, iCESM, iHadCM3, and isoGSM) over the last millennium (850–1850 CE). We systematically evaluate differences and commonalities between the standardized model simulation outputs. The goal is to distinguish climatic drivers of variability for modeled isotopes and compare them to those of measured isotopes. We find strong regional differences in the oxygen isotope signatures between models that can partly be attributed to differences in modeled surface temperature. At low latitudes, precipitation amount is the dominant driver for stable water isotope variability; however, at cave locations the agreement between modeled temperature variability is higher than for precipitation variability. While modeled isotopic signatures at cave locations exhibited extreme events coinciding with changes in volcanic and solar forcing, such fingerprints are not apparent in the speleothem isotopes. This may be attributed to the lower temporal resolution of speleothem records compared to the events that are to be detected. Using spectral analysis, we can show that all models underestimate decadal and longer variability compared to speleothems (albeit to varying extents). We found that no model excels in all analyzed comparisons, although some perform better than the others in either mean or variability. Therefore, we advise a multi-model approach whenever comparing proxy data to modeled data. Considering karst and cave internal processes, e.g., through isotope-enabled karst models, may alter the variability in speleothem isotopes and play an important role in determining the most appropriate model. By exploring new ways of analyzing the relationship between the oxygen and carbon isotopes, their variability, and co-variability across timescales, we provide methods that may serve as a baseline for future studies with different models using, e.g., different isotopes, different climate archives, or different time periods.

Published and unpublished iron isotope data from banded iron formations (BIF) and their BIF-hosted hypogene (hydrothermal) iron ores from the Quadrilátero Ferrífero (itabirites), Corumbá, and Carajás iron districts in Brazil, as well as from the Hamersley province in Australia are presented and discussed. BIF constitutes a typically thinly bedded or laminated chemical sedimentary rock, with ≥ 15% Fe and layers of chert, chalcedony, jasper, or quartz, whereas itabirite is considered a laminated, metamorphosed iron formation rich in iron oxides, which may contain carbonate minerals, amphiboles, and abundant quartz. For the Paleoproterozoic Quadrilátero Ferrífero district, the range in δ56Fe values of hypogene iron ores is similar to that of the metamorphosed BIFs, and iron isotope variations are better distinguished in different regional deformational domains. Light isotopic compositions dominate in the low deformation domain (δ56Fe = −0.42 ± 0.12 to 0.29 ± 0.04‰), whereas the eastern, high-strain domain is characterized by heavy values (δ56Fe = −0.09 ± 0.08 to 0.37 ± 0.06‰; Mendes et al., Mineral Deposita 52:159–180, 2017). Iron isotope composition for the Neoproterozoic iron formations of the Corumbá region (hematitic, dolomite-rich: −1.83 and −0.83‰; cherty-hematite: δ56Fe −0.49‰) are controlled by: (1) primary seawater signature, (2) microbial activity, and (3) supergene goethite alteration. Hydrothermal alteration is reflected in the oxygen isotope data, but apparently not in the iron isotope fractionation. Iron and oxygen isotope pairing shows that δ56Fe values increase, while δ18O values decrease. In the Archean jaspilites of Carajás, hypogene ores tend to display lighter δ56Fe values than their host BIF counterparts. Also, there is a correlation between coupled iron and oxygen isotope values that is clearer towards lighter isotopic values, especially for δ18O. In the Paleoproterozoic Hamersley deposits, correlation between δ18O and δ56Fe values suggests a direct correlation of both isotope systems during low-grade, greenschist-facies metamorphism. On the other hand, despite the evident shift to negative δ18O values and apparent preservation of the metamorphic δ56Fe signature, iron ore and hydrothermally modified BIF show a correlation between δ18O and δ56Fe values. In contrast, in supergene-modified samples a negative correlation is apparent. The Carajás (+1.24 to + 0.44; one sample − 0.30‰) and Hamersley (+ 1.02 to − 0.29‰) hypogene ores display δ56Fe in a similar interval, reaching positive values, whereas ores from the Quadrilátero Ferrífero show a tendency towards lower values (to − 0.80‰). This review indicates that the application of iron isotopes in exploration is presently limited mainly due to the restricted dataset available for ore samples. Nevertheless, and despite all local differences, there is a general tendency for hypogene ores to display moderately lighter δ56Fe values for all deposits compared to precursor BIF. In contrast, a strong supergene imprint in ore leads to moderately heavier δ56Fe values. As more data become available, and if these trends are confirmed, the use of this tool may be valuable in the future, for instance to decipher the hypogene or supergene origin of specific ore zones, and as a consequence the probable depth extension or interpretation of concealed, deep orebodies.

Fluid inclusion, H–O isotope and Pb–Pb age constraints on the genesis of the Yongping copper deposit, South China

Fluid evolution and metallogenic mechanism of the Xianghualing skarn-type Sn deposit, South China: Evidence from petrography, fluid inclusions and trace-element composition of cassiterite

&amp;lt;p&amp;gt;Oxygen isotope analysis of plant material, such as sugars in different tissues, provides an important tool to understand how plants function, interact with their environment and also cope with climate change. Knowing how to extract and purify carbohydrates without artificially altering their oxygen isotope ratio (&amp;lt;em&amp;gt;&amp;amp;#948;&amp;lt;/em&amp;gt;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O) is therefore essential.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We aimed to resolve the impact of different steps on sugars' &amp;lt;em&amp;gt;&amp;amp;#948;&amp;lt;/em&amp;gt;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O values during their extraction and purification from leaf and phloem tissue. More precisely, we investigated (1) different drying processes (oven- vs freeze-drying), and (2) how extraction and purification affect leaf sugars. To clearly see fractionation and exchange processes, these experiments were performed using &amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O-labelled water. We further examined (3) the influence of different EDTA media and immersion times to facilitate sugar exudation and subsequent yield from twig phloem tissue. Finally, we analysed (4) the sugar phloem composition, as well as the individual compounds&amp;amp;#8217; carbon isotopic signatures (&amp;lt;em&amp;gt;&amp;amp;#948;&amp;lt;/em&amp;gt;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C).&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Comparison of freeze- and oven-dried sugars showed lower &amp;lt;em&amp;gt;&amp;amp;#948;&amp;lt;/em&amp;gt;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O memory effects and more consistent oxygen isotopic signatures across different sugars, indicating lyophilisation as the more reliable method. The extraction and purification can be conducted without significant oxygen isotope fractionation. However, &amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O-depletion was observed when sugars were dissolved and dried multiple times. This suggests that additional dissolution and drying steps should best be avoided whenever possible. Different immersion times and exudation media during twig phloem extraction revealed to have a substantial influence on the phloem sugars' overall oxygen isotopic signature, their composition, and the individual compounds' &amp;lt;em&amp;gt;&amp;amp;#948;&amp;lt;/em&amp;gt;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C values.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Our research illustrates which precautions during sample preparation &amp;amp;#8211; from drying to extracting and purifying &amp;amp;#8211; need to be taken when plant sugars and their oxygen isotopic signature are of interest. Regarding the preservation of the phloem sugars' original &amp;lt;em&amp;gt;&amp;amp;#948;&amp;lt;/em&amp;gt;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O values and stabilising their composition (prevention of sucrose degradation) as much as possible, we recommend a short immersion time of approx. 1 hour. After a thorough initial rinse of the tissue, the sap should be eluted in pure water without any additives (no EDTA). This further reduces the possibility of hexoses to exchange oxygen with that of the surrounding water.&amp;lt;/p&amp;gt;

The Marcona–Mina Justa deposit cluster, hosted by Lower Paleozoic metaclastic rocks and Middle Jurassic shallow marine andesites, incorporates the most important known magnetite mineralization in the Andes at Marcona (1.9 Gt at 55.4% Fe and 0.12% Cu) and one of the few major iron oxide–copper–gold (IOCG) deposits with economic Cu grades (346.6 Mt at 0.71% Cu, 3.8 g/t Ag and 0.03 g/t Au) at Mina Justa. The Middle Jurassic Marcona deposit is centred in Ica Department, Peru, and the Lower Cretaceous Mina Justa Cu (Ag, Au) prospect is located 3–4 km to the northeast. New fluid inclusion studies, including laser ablation time-of-flight inductively coupled plasma mass spectrometry (LA-TOF-ICPMS) analysis, integrated with sulphur, oxygen, hydrogen and carbon isotope analyses of minerals with well-defined paragenetic relationships, clarify the nature and origin of the hydrothermal fluid responsible for these contiguous but genetically contrasted deposits. At Marcona, early, sulphide-free stage M-III magnetite–biotite–calcic amphibole assemblages are inferred to have crystallized from a 700–800°C Fe oxide melt with a δ18O value from +5.2‰ to +7.7‰. Stage M-IV magnetite–phlogopite–calcic amphibole–sulphide assemblages were subsequently precipitated from 430–600°C aqueous fluids with dominantly magmatic isotopic compositions (δ34S = +0.8‰ to +5.9‰; δ18O = +9.6‰ to +12.2‰; δD = −73‰ to −43‰; and δ13C = −3.3‰). Stages M-III and M-IV account for over 95% of the magnetite mineralization at Marcona. Subsequent non-economic, lower temperature sulphide–calcite–amphibole assemblages (stage M-V) were deposited from fluids with similar δ34S (+1.8‰ to +5.0‰), δ18O (+10.1‰ to +12.5‰) and δ13C (−3.4‰), but higher δD values (average −8‰). Several groups of lower ( 200°C) fluids can be recognized in the main polymetallic (Cu, Zn, Pb) sulphide stage M-V and may record the involvement of modified seawater. At Mina Justa, early magnetite–pyrite assemblages precipitated from a magmatic fluid (δ34S = +0.8‰ to +3.9‰; δ18O = +9.5‰ to +11.5‰) at 540–600°C, whereas ensuing chalcopyrite–bornite–digenite–chalcocite–hematite–calcite mineralization was the product of non-magmatic, probably evaporite-sourced, brines with δ34S ≥ +29‰, δ18O = 0.1‰ and δ13C = −8.3‰. Two groups of fluids were involved in the Cu mineralization stage: (1) Ca-rich, low-temperature (approx. 140°C) and high-salinity, plausibly a basinal brine and (2) Na (–K)-dominant with a low-temperature (approx. 140°C) and low-salinity probably meteoric water. LA-TOF-ICPMS analyses show that fluids at the magnetite–pyrite stage were Cu-barren, but that those associated with external fluids in later stages were enriched in Cu and Zn, suggesting such fluids could have been critical for the economic Cu mineralization in Andean IOCG deposits.

The Qiubudong silver deposit on the western margin of the Fuping ore cluster in the central North China Craton is a representative breccia-type deposit characterized by relatively high-grade ores, thick mineralized zones, and extensive alteration, indicating considerable potential for economic resource development and further exploration. Previous studies on this deposit have not addressed its genetic mineralogical characteristics. This study focuses on pyrite and quartz to investigate their typomorphic features, such as crystal morphology, trace element composition, thermoelectric properties, and luminescence characteristics, and their implications for ore-forming processes. Pyrite crystals are predominantly cubic in early stages, while pentagonal dodecahedral and cubic–dodecahedral combinations peak during the main mineralization stage. The pyrite is sulfur-deficient and iron-rich, enriched in Au, and relatively high in Ag, Cu, Pb, and Bi contents during the main ore-forming stage. Rare earth element (REE) concentrations are low, with weak LREE-HREE fractionation and a strong negative Eu anomaly. The thermoelectric coefficient of pyrite ranges from −328.9 to +335.6 μV/°C, with a mean of +197.63 μV/°C; P-type conduction dominates, with an occurrence rate of 58%–100% and an average of 88.78%. A weak–low temperature and a strong–high temperature peak characterize quartz thermoluminescence during the main mineralization stage. Fluid inclusions in quartz include liquid-rich, vapor-rich, and two-phase types, with salinities ranging from 10.11% to 12.62% NaCl equiv. (average 11.16%) and densities from 0.91 to 0.95 g/cm3 (average 0.90 g/cm3). The ore-forming fluids are interpreted as F-rich, low-salinity, low-density hydrothermal fluids of volcanic origin at medium–low temperatures. The abundance of pentagonal dodecahedral pyrite, low Co/Ni ratios, high Cu contents, and complex quartz thermoluminescence signatures are key mineralogical indicators for deep prospecting. Combined with thermoelectric data and morphological analysis, the depth interval around 800 m between drill holes ZK3204 and ZK3201 has high mineralization potential. This study fills a research gap on the genetic mineralogy of the Qiubudong deposit and provides a scientific basis for deep exploration.

The Sijiaying iron deposit is located in the Eastern Hebei area of the southern section of the northern margin of the North China Craton (NCC) and is the largest single iron deposit in China. The deposit contains many banded iron formations (BIFs) and was proven to have more than 3 million tons of high-grade iron ore resources. This study carried out geochemistry and zircon U–Pb analysis of normal-grade iron ore, high-grade iron ore, and wall rock (biotite–leptynite, chlorite–sericite schist) in the Sijiaying deposit and discussed the genesis and metallogenic age of high-grade iron ore. BIFs have low concentrations of Al2O3 and TiO2 and high field strength element (HFSE) depletion, indicating almost no contamination via terrestrial debris. The standardized post-Archean Australian shale (PAAS) rare earth element (REE) distribution pattern indicates that the iron formation exhibits positive Eu, Y, and heavy rare earth element (HREE) anomalies and lacks negative Ce anomalies, indicating that the Sijiaying BIF was enriched with iron sources via high-temperature hydrothermal fluids from the seabed and deposited in an anoxic ancient marine environment. In addition, geological field work identified two types of high-grade iron ore in the mining area: primitive sedimentary and hydrothermally altered high-grade iron ore. Further ore geochemical research showed that the primitive sedimentary-type iron ore is similar in geochemistry to the BIF. In addition to low Eu/Eu* values, the hydrothermally altered high-grade iron ore shows geochemical characteristics similar to those of the BIF, suggesting that they share the same iron source but did not form at the same time. The total large ion lithophile element (LILE) (Sr, Ba, Pb) contents in primitive sedimentary-type high-grade iron ore are higher than those in hydrothermally altered high-grade iron ore, indicating that LILEs are carried away via fluids during the hydrothermal alteration process in normal-grade iron ore. The geochemical characteristics of biotite–leptynite and chlorite–sericite schist include high contents of SiO2 and Al2O3, light rare earth elements (LREEs), LILE enrichment (Rb, Ba, Sr, Zr), and HFSE depletion (Nb, Ta, P, Ti), characteristics that are similar to island arc volcanic rocks. The reconstruction of the original rock indicates that the wall rock is a product of volcanic sedimentary cycles in an island arc setting. Zircon cathodoluminescence images and LA–ICP–MS zircon U–Pb dating can be divided into four age groups (3283 Ma, 2547 Ma, 2500 Ma, and 2407 Ma), which correspond to the earliest volcanic activity in eastern Hebei, the main mineralization age of the Sijiaying BIF (the mineralization age of primitive sedimentary high-grade iron ore), a regional tectonic–metamorphic event, and the occurrence of migmatization (the mineralization age of hydrothermally altered high-grade iron ore), respectively. Therefore, the Sijiaying BIF and primitive sedimentary high-grade iron ores were deposited and mineralized at 2547 Ma, and the iron orebody was later altered via the hydrothermal solution at 2407 Ma, forming large-scale high-grade iron ores.

The Wangjiazhuang Cu (‐Mo) deposit, located within the Zouping volcanic basin in western Shandong Province, China, is unique in this area for having an economic value. In order to expound the metallogenetic characteristics of this porphyry‐like hydrothermal deposit, a detailed fluid inclusion study has been conducted, employing the techniques of representative sampling, fluid inclusion petrography, microthermometry, Raman spectroscopy, LA‐ICP‐MS analysis of single fluid inclusions, as well as cathode fluorescence spectrometer analysis of host mineral quartz. The deposit contains mainly two types of orebodies, i.e. veinlet‐dissemination‐stockwork orebodies in the K‐Si alteration zone and pegmatitic‐quartz sulfide veins above them. In addition, minor breccia ore occurs locally. Four types of fluid inclusions in the deposit and altered quartz monzonite are identified: L‐type one‐ or two‐phase aqueous inclusions, V‐type vapor‐rich inclusions with V/L ratios greater than 50%–90%, D‐type multiphase fluid inclusions containing daughter minerals or solids and S‐type silicate‐bearing fluid inclusions containing mainly muscovite and biotite. Ore petrography and fluid inclusion study has revealed a three‐stage mineralization process, driven by magmatic‐hydrothermal fluid activity, as follows. Initially, a hydrothermal fluid, separated from the parent magma, infiltrated into the quartz monzonite, resulting in its extensive K‐Si alteration, as indicated by silicate‐bearing fluid inclusions trapped in altered quartz monzonite. This is followed by the early mineralization, the formation of quartz veinlets and dissemination‐stockwork ores. During the main mineralization stage, due to the participation and mixing of meteoric groundwater with magmatic‐sourced hydrothermal fluid, the cooling and phase separation caused deposition of metals from the hydrothermal fluids. As a result, the pegmatitic‐quartz sulfide‐vein ores formed. In the late mineralization stage, decreasing fluid salinity led to the formation of L‐type aqueous inclusions and chalcopyrite‐sulfosalt ore. Coexistence of V‐type and D‐type inclusions and their similar homogenization temperatures with different homogenization modes suggest that phase separation or boiling of the ore‐forming fluids took place during the early and the main mineralization stages. The formation P‐T conditions of S‐type inclusions and the early and the main mineralization stages were estimated as ca. 156–182 MPa and 450–650°C, 350–450°C, 18–35 MPa and 280–380°C, 8–15 MPa, respectively, based on the microthermometric data of the fluid inclusions formed at the individual stages.

Paleoceanographic changes during the early Cretaceous (Valanginian–Hauterivian): evidence from oxygen and carbon stable isotopes

The Xiong’ershan district is situated on the southern margin of the North China Craton (NCC) and located within the Qinling–Dabieshan Orogen’s orogenic zone. It is adjacent to the XiaoQinling mining district and exhibits very favorable geological conditions for mineralization, as the district contains numerous gold deposits, positioning it as one of the key gold-producing areas of China. The Miaoling gold deposit is a hydrothermal deposit and is controlled by the Mesozoic nearly NS-trending fault. The ore bodies are hosted in the Mesoproterozoic Xiong’er Group of the Changcheng System of volcanic rocks, with reserves reaching large-scale levels. Pyrite is the main gold-bearing mineral and can be classified into four generations: early-stage fine- to medium-grained euhedral to subhedral cubic pyrite (Py1); medium- to coarse-grained euhedral to subhedral cubic granular pyrite in quartz veins (Py2a); fine-grained subhedral to anhedral disseminated pyrite in altered rocks (Py2b); and late-stage anhedral granular and fine-veinlet pyrite in later quartz veins (Py3). Through in situ trace element analysis of the pyrite using LA-ICP-MS, a positive correlation between Au and As was observed during the main mineralization stage; gold mainly exists as a solid solution within the pyrite lattice, and the ablation signal curve reflecting the intensity of trace element signals showed that gold also occurs as micron-scale mineral inclusions. The trace element content suggested a gradual increase in oxygen fugacity from Stage 1 to Stage 2, followed by a decrease from Stage 2 to Stage 3. The Co/Ni values in the pyrite (0.56 to 62.02, with an average of 12.34) exhibited characteristics of magmatic hydrothermal pyrite. The in situ sulfur isotope analysis of the pyrite using LA-MC-ICP-MS showed δ34S values of 4.24‰ for Stage 1, −6.63‰ to −13.79‰ for Stage 2, and −4.31‰ to −5.15‰ for Stage 3. Considering sulfur isotope fractionation, the δ34S value of the hydrothermal fluid during the main mineralization stage was calculated to be between 0.31‰ and 2.68‰.

Metallogeny of the Northern Norrbotten Ore Province, northern Fennoscandian Shield with emphasis on IOCG and apatite-iron ore deposits

Strontium and oxygen isotopes of individuals from El Hundido and Valdescusa (north of Spain) sites, corresponding to the Bell Beaker culture, were analysed in order to determine mobility patterns and provenance areas. Strontium and oxygen isotope ratios in three teeth from two individuals at El Hundido and two teeth from the five individuals at Valdescusa were studied. The analyses were performed in both dentine and enamel fractions. 87Sr/86Sr ratios of El Hundido individuals indicate one was of foreign origin and the other was local whereas at Valdescusa were all of foreign provenance. Calculated δ18Ow values of El Hundido suggest a provenance from the geographical area close to the site while the Valdescusa would come from a warmer region. The comparison of oxygen and strontium isotope signatures indicate the west of the Iberian Peninsula (Zamora or the east of Leon regions) as the provenance area for the foreign individual at El Hundido and southwest France (Garonne basin) as the region of provenance for the Valdescusa.