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The mafic-ultramafic intrusion in the XV anomaly area, contains magmatic Fe-Ti ox-ides±(p) ore, is located in the Bafq mining district in the Central Iran. It consists of cumulate and layered Fe-Ti-bearing gabbros and pyroxenites. The mineral assemblages include clinopyroxene, Fe-Ti oxides, plagioclase, amphibole, apatite and sulfides (pyrite and chalcopyrite). The Fe-Ti oxides mainly consist of magnetite-titanomagnetite and ilmenite, which occurred as disseminated, intergrowth, lamellae (trellis and sandwich textures) and inclusions. Magnetite in the gabbroic rocks is from the near end-member of Fe3O4 (<1 wt.% TiO2) to titanomagnetite containing up to 8 wt.% TiO2 (about 3.73 wt.% to 26.84 wt.% Ulvospinel (XUsp)). Magnetite in pyroxenite rocks is characterized with TiO2 range from 0.46 wt.% to 3.14 wt.% (XUsp varied from 1.76 wt.% to 10.46 wt.%). The abundances of V2O3 range from 0.03 wt.% to 1.29 wt.% and 0.24 wt.% to 1.00 wt.% for gabbro and pyroxenite, respectively. XUsp contents of magnetite show insignificant correlations with Al2O3 and MgO. The average XIlm in the ilmenite of gabbro is 92%, whereas it is 90.37% in the pyroxenite rocks. The MgO and V2O3 contents show a slightly positive correlation with TiO2 in ilmenite. The composition of clinopy-roxenes in gabbro and pyroxenite rocks fall in the diopside to augite field with Mg# ranging from 67 to 98 and 74 to 96, respectively. In both rock types, amphiboles are mainly pargasite and rarely actin-olite. Plagioclase in pyroxenite rocks is clustered in the labradorite to andesine fields with a compositional ranges of An46–69 and in gabboic rocks fall in two fields with compositional ranges of albite with An0.65–5.95 and labradorite with An50–63. The δ 34S isotopic values cover a limited range from +3.15‰ to +4.10‰ V-CDT consistent with magmatic origin. Fe-Ti mineralization is formed in two stages, minor inclusions of Fe-Ti oxide minerals in the pyroxene and plagioclase crystallized in the early magmatic stage, whereas interstitial oxides formed by fractional crystallization processes that accumulated by gravitational settling in the later stage as intercumulus phase. Gravitational settling process is supported by the observation of decreasing the amount of Fe-Ti oxides from Fe-Ti oxide-rich pyroxenite to weak mineralized gabbro (base to top). The high contents of H2O, phosphorate and high initial Ti-Fe in parental magma are the crucial factors controlling the Fe-Ti oxides enrichment and mineralization. [ABSTRACT FROM AUTHOR]

The destruction of the cratonic root has been documented for multiple cratons worldwide and is characterized by severe lithospheric thinning, extensive extensional deformation, and intense thermal activity. Here, we present detailed petrography accompanied by comprehensive geochemical and isotopic data for peridotites, pyroxenites, and eclogites from the SW margin of the São Francisco Craton that has also been severely thinned. The diamond-bearing Canastra-1 kimberlite represents a Cretaceous intrusion from the Alto Paranaíba Igneous Province and hosts garnet-bearing mantle xenoliths from different mantle sources, revealing a complex history of metasomatism/refertilization related to superimposed tectonic events since the cratonic consolidation. Eclogites (T = 978–982°C; P ~ 4.0 GPa) and pargasite-bearing websterites (T = 875–926°C; P = 2.0–3.0 GPa) represent the shallower and colder cratonic lithosphere. Mantle-derived high-MgO eclogitic clinopyroxenes show a light rare earth element (LREE)-enriched pattern (Ce/YbN = 60.90–93.63) while both clinopyroxene and garnet present high 87Sr/86Sr ratios (0.70842–0.70912) and negative εNd values (−5.6 to −7.3). These features, supported by the reconstructed whole-rock composition, suggest a mafic protolith probably metasomatized by fluid/melt derived from the overlying sedimentary rocks. Pargasite websterites are cumulates from an evolved (SiO2-rich) and hydrated basaltic andesitic magma. These xenoliths are characterized by high concentration of LREE relative to heavy-REE (HREE) in clinopyroxene (Ce/YbN = 10.52–50.61) and pargasite (Ce/YbN = 10.26–57.06), and by the presence of Al-rich orthopyroxene. As observed in eclogites, clinopyroxene and garnet from pargasite websterites display high 87Sr/86Sr ratios (0.70894–0.71094) and strong negative εNd values (−7.2 to −13.3). Trace elements (i.e. Zr, Ti, and Y) in garnets of both rock types indicate the role of a depleted component affected by a metasomatic agent. Although we were unable to date the formation of these rocks or the metasomatic events, we suggest a possible relationship with the consolidation of Gondwana during the Neoproterozoic. Sheared lherzolites, clinopyroxenites, anhydrous websterites, and dunite are deeper fragments from the lithosphere-asthenosphere boundary (LAB: 1191–1290°C; 5.3–5.6 GPa). They have abundant kelyphitic rims around garnet grains, which indicate metasomatism promoted by the percolation of a high-temperature proto-kimberlite melt enriched in Ti, Zr, and Y. The presence of kelyphitic phlogopite with high-Ti-Cr contents reinforces this assumption. LREE-enriched clinopyroxenes (Ce/YbN = 12.06–48.02) confirm the enriched character of the silicate melt responsible for the refertilization process within the cratonic root. The proto-kimberlite metasomatism is further supported by the preferential enrichment of 87Sr/86Sr ratios (0.70560–0.70869) accompanied by positive εNd values (+1.8 to +10.10). Two-point clinopyroxene-garnet Sm–Nd isochrons yielded an average age of 120 ± 5 Ma, representing the kimberlite eruption/emplacement age of the host kimberlite. These deeper LAB xenoliths reveal intense lithospheric thinning triggered by percolation of a high-temperature proto-kimberlite melt since the early stages of Gondwana break-up during the Cretaceous, shortly before the kimberlite emplacement at 120 Ma. Therefore, they provide remarkable evidence of the destruction of the São Francisco Craton through thermal-mechanical erosion that triggered its rejuvenation. [ABSTRACT FROM AUTHOR]

The Hongnipo deposit, a newly discovered large copper deposit in the Kangdian Fe-Cu metallogenic belt of southwest China, is hosted in the Paleoproterozoic metavolcanic and metasedimentary rocks of the Hekou group. The deposit comprises five strata-bound ore bodies and is associated with sporadically distributed gabbroic intrusions. Four stages of mineralization and alteration have been identified: sodic alteration (I), banded sulfide (II), magnetite (III), and sulfide vein/stockwork (IV). Extensive sodic alteration of stage I is confirmed by the composition of feldspars. Trace element analysis of magnetite suggests a formation temperature of 400 ± 50 °C and has a characteristic of IOCG deposits, while high δ18O values (8.3–11.0‰) of fluids from stage III indicate a magmatic water origin. Sulfide δ34SVCDT values from stages II and IV range from −2.6 to 10.9‰ and −1.5 to 9.9‰, respectively, suggesting a mixed sulfur source from magmatic H2S and reduced seawater sulfate. Chalcopyrite from Hongnipo shows a narrow δ65Cu range of −0.135 to 0.587‰, indicating formation at high temperatures. The lack of correlation between δ65Cu and δ34SVCDT values suggests distinct geochemical behaviors in mineralization. In summary, the Hongnipo deposit is classified as a Cu-rich section of a typical IOCG deposit. [ABSTRACT FROM AUTHOR]

Intermediate sulfidation epithermal deposits represent significant reservoirs of precious metals, playing a crucial role in global mining operations. The Anatolian Peninsula, predominantly characterized by relatively young (Tertiary) lithologies, hosts numerous occurrences of epithermal base and precious metal mineralization. Within the realm of research in Northeastern Anatolia, several hydrothermal alteration zones have emerged as indicators of concealed epithermal mineralization, with the Bahçecik mineralization standing out as a recent focal point. The Bahçecik mineralization represents an intermediate sulfidation epithermal Au-Ag system, hosted by Late Cretaceous andesitic rocks, as well as Eocene dacitic lava and tuffs. Employing U-Pb LA-ICP-MS zircon dating of the dacitic host rocks, the mineralization is estimated to have occurred during the Lutetian epoch (43.61 ± 0.35 Ma) or later. The genesis of the Bahçecik deposit is believed to be linked to postcollisional regional extensional tectonics, primarily controlling its structural arrangement. Comprising pyrite, chalcopyrite, low-Fe sphalerite, galena, tetrahedrite/tennantite, enargite-luzonite, and gold-silver minerals, the deposit is accompanied by prominent gangue minerals such as Mn- and Ca-carbonates, quartz, and barite. Microprobe measurements have identified a majority of Au-Ag minerals (krennerite, buckhornite, and nagyagite) closely associated with sulphide minerals. Fluid inclusion data reveal that mineralization and fluid transportation occurred at temperatures ranging from 153 to 327°C, with solutions exhibiting salinity levels consistent with those of intermediate sulfidation deposits (1.7–7.3 wt.% NaCl). This study unequivocally classifies the Bahçecik mineralization as an intermediate sulfidation deposit, contrary to the conclusions drawn in previous research. Moreover, our investigation has unveiled the presence of a substantial ore resource, totalling 7.84 million tons, featuring 1.76 g/t Au and 2.24 g/t Ag. As an intermediate-type deposit, it shares characteristics with other subtypes within the epithermal class, bridging the realms of both high and low sulfidation systems. [ABSTRACT FROM AUTHOR]

Garnets are observed as phenocrysts in blocky rhyolites of Cumaovası Volcanites and are reddish-blackish in color, show vitreous luster, and have dodecahedron forms varying between 0.5 and 2.0 cm in size. In optical microscope investigations, they exhibit fractured structures and contain quartz, hematite, chlorite, and acicular rutile inclusions. Garnet phenocrysts are highly consistent with spessartine-type garnet end members in the Raman spectrum. This result is supported by the mineral chemistry results determined as spessartine (Sps)0.50–0.52 almandine (Alm)0.47–0.48 grossular (Grs)0.01–0.02. In the chondrite, primitive mantle, and Mid-Oceanic Ridge Basalt normalized multi element variation diagrams, garnet phenocrysts show enrichment in all elements (except Sr, K, P, and Ti). In contrast, in the upper continental crust normalized multi element variation diagram, garnet phenocrysts show depletion in large ion lithophile elements (Rb, Ba, K, and Sr) relative to high field strength elements. They exhibit slight enrichment in light rare earth elements ((La/Sm)N = 0.11–1.07) relative to heavy rare earth elements ((Sm/Yb)N=0.78–0.97). Furthermore, garnet phenocrysts have significant negative europium (Eu) ((Eu/Eu*)N = 0.01–0.02) and mildly positive cerium ((Ce/Ce*)N = 2.43–13.77) anomalies indicating hot and reduced magma conditions. The Y/Ho ratios have ranged from 18.9 to 20.3 and are close to the chondrite value. The zircon saturation temperatures (TZr) of the garnet's host rock was determined to be 756 °C. As a result of mineralogical, geochemical and gemological studies, it was concluded that Görece garnet phenocrysts have glassy luster and semi-transparent dodecahedral crystal shapes, so they can be classified as semi-precious gemstones. In addition, the rare earth element content of the garnet phenocrysts is similar to that of industrial garnet sands and it is thought that they may have potential. [ABSTRACT FROM AUTHOR]

The mineral chemistry, whole-rock geochemistry, 40Ar / 39Ar dating and Sr-Nd-Pb-Hf isotopes of the Eocene Narman (Erzurum) Volcanic rocks in the southeast of the Eastern Pontides Orogenic Belt (EPOB, NE Türkiye) were investigated. The Narman Volcanites consist of basaltic dyke, basaltic lava, and basaltic volcanic breccia facies. Volcanites contain plagioclase (An34-80), clinopyroxene (Wo38-47En41-50Fs5-18), and olivine (Fo68-90) as phenocrystals with magnetite/titanomagnetite microphenocrysts. New 40Ar-39Ar ages suggest that these volcanic rocks erupted between 44.5 ± 0.1 and 43.4 ± 0.1 Ma, within the Middle Eocene (Lutetian). Narman Volcanites have calcalkaline character, with medium-high K content. Volcanites are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), while they are depleted in terms of high field strength elements (HFSE). Chondrite-normalized rare earth element distributions have concave shape with moderate enrichment (LaN/LuN = 2.78–7.99), leading to consideration that the magmas forming the volcanics derived from similar sources. Isotopically, the rocks in the Narman Volcanites have low-medium initial 87Sr/86Sr values (0.70405–0.70485), initial 143Nd/144Nd values (0.512606–0.512848) and positive Ndi (+0.5 – +5.2). Depleted mantle Nd model ages were TDM1 = 0.29–0.62 Ga and TDM2 =0.43–0.83 Ga. (206Pb/204Pb)i, (207Pb/204Pb)i, and (208Pb/204Pb)i values vary in the ranges of 18.246–18.709, 15.578–15.616, and 38.225–38.791, respectively. The initial (176Hf/177Hf)i ratios for the volcanites are between 0.282770 and 0.283013, while the εHf values range from +7.6 to +9. All the evidence supports the conclusion that the parental magma for the rocks probably derived from an enriched lithospheric mantle, previously metasomatized by fluids derived from subducted slab during asthenospheric upwelling, due to fragmented asymmetric delamination in a postcollisional extensional tectonic environment. [ABSTRACT FROM AUTHOR]

The subduction-related Sunda-Banda arc hosts several giant and major Cu–Au–Mo porphyry and epithermal Au systems, making it one of the most important magmatic-related metallogenic belts in Indonesia. They are accompanied by a number of smaller systems, one of which is the recently discovered Randu-Kuning porphyry Cu-Au deposit on Java Island. The present study investigates the geochemical characteristics of this deposit through whole-rock and mineral geochemistry and mineral geothermobarometry, focusing on three sequential dioritic intrusions that make up the host igneous complex, two barren and the third mineralized. Moreover, a comparative analysis is performed between other porphyry deposits in the Sunda-Banda arc and with Grasberg in Papua. This study shows that the older porphyry deposits have mostly similar geochemical characteristics to the younger deposits, suggesting the same magma source, which is mantle-derived oxidized I-type magma. Amphibole geothermobarometry shows that the formation of syn-ore intrusion in the older porphyry was higher in temperature and pressure than those at the younger porphyry. The halogen and oxygen fugacities inferred from biotite and amphibole chemistry indicate an oxidized, water- and halogen-rich melt. Our study shows that combining amphibole and biotite chemistry and whole-rock geochemical data is useful to fingerprint the magmatic-hydrothermal processes, especially where multiple magmatic phases occur. This research also provides valuable insights into the magmatic-hydrothermal physiochemical conditions during the formation of the mineralized system. [ABSTRACT FROM AUTHOR]

This paper investigates the mineralogical and geochemical characteristics, as well as the possible sources, of gold, silver, platinum group elements (PGE), copper, and lead found in the beach sands along Egypt's Mediterranean coast. Using scanning electron microscopy and electron probe micro-analysis, this study determines the morphology and micro-chemistry of separated grains to assess their economic potential and how various minerals respond to different transport distances. The analysis reveals that gold grains are of high purity (94.11 to 98.55 wt.%; average 96 wt.% Au) and are alloyed with Ag (1.28–2.32 wt.%) and Cu (0.16–3.15 wt.%). Two types of gold grains were identified, indicating differences in transport distances. Variations in morphology, surface features, inclusion types, rims, and chemistry of the native metals, including gold grains, suggest differences in composition, weathering degree, transport distance, deposit types, and host rocks. The average Ag concentration in gold grains (1.86 wt.%) suggests a link to mesothermal or supergene deposits. Most silver, copper, and lead grains are spherical, with some variations in shape. Silver grains have 71.66–95.34 wt.% Ag (avg. 82.67 wt.%). Copper grains have 92.54–98.42 wt.% Cu (avg. 94.22 wt.%). Lead grains contain 74.22–84.45 wt.% Pb (avg. 79.26 wt.%). The identified platinum group minerals (PGM) belong to the Pt–Fe alloys and sperrylite, both of which are PPGE-bearing minerals. These metals likely originate from the weathering of upstream Nile tributaries surrounded by igneous and metamorphic rocks from Ethiopian and Central African regions, with a minor contribution from the Egyptian Eastern Desert Mountains. [ABSTRACT FROM AUTHOR]

Elazığ volcanites, defined within the Eastern Anatolian Volcanic Province, are distributed in three regions (Cip, Harput, Yeniköy) around the center of Elazığ. While the lava of volcanites consisting of effusive and explosive volcanism products do not form thick stacks, pyroclastics, which generally form basaltic slag cones, have a relatively much thicker thickness. Petrographic examinations of the lavas have shown that the main mineral composition consists of weakly altered, porphyritic, vesicular and flow-textured olivine basalts consisting of plagioclase, olivine and pyroxene minerals, and alkaline basalts containing nepheline and leucite. According to mineral chemistry analysis data, while labradorite is the most common plagioclase mineral in all samples, a change from anorthite to sanidine is observed in Yeniköy samples and from andesine to sanidine in Harput samples. Pyroxene minerals have a bronzite and diopside composition and appear to crystallize from a system with high Mg and Ca content. In the variation diagrams related to minerals, weak differences are observed between the samples depending on their mineral composition. In terms of olivine mineral content, Cip village samples are relatively poorer in Al, Mn and Ca than pyroxene minerals, but richer in Fe and Mg, although they are particularly weak in Mg and rich in Ca content, compared to Harput samples. The orientations of the element contents of petrographic and mineral compositions indicate that these volcanics may be the product of two differentiated magmas formed under low pressure conditions, affected by the magma mixture along with fractionation. The fact that amphiboles also have magmatic and metamorphic properties suggests that metasomatism and the subduction components that because it may be important in magma differentiation. [ABSTRACT FROM AUTHOR]

Upper Cretaceous–Miocene alkaline SiO2-undersaturated volcanic rocks in the southern Central European Volcanic Province (CEVP) comprise two distinct rock series: (i) Upper Cretaceous–Eocene (~73–47 Ma) olivine nephelinites, basanitic nephelinites, and nepheline basanites have moderate to high MgO (8–16 wt. %), CaO, Ni, Co, Cr, Nb, and Ba, coupled with low F and SiO2 concentrations. These rocks contain abundant clinopyroxene and variable amounts of olivine macrocrysts as well as nepheline, K-dominated F-poor mica, and hydroxyapatite. Evolved and less common apatite-rich (phonolitic) haüynites/noseanites and haüyne nephelinites (~68–62 Ma) represent differentiated counterparts within this older group, showing higher alkali, Al2O3, P2O5, Nb, Zn, REE, and SO3 concentrations at low MgO (4–6 wt. %), CaO, Ni, Co, and Cr contents. (ii) Oligocene–Miocene (~27–9 Ma) olivine melilitites and melilite-bearing olivine nephelinites are characterized by even higher MgO (10–22 wt. %), CaO, Ni, Co, Cr, Nb, Ba, and high F contents at lower SiO2 concentrations, as reflected by the presence of abundant olivine macrocrysts, melilite, perovskite, Cr-rich spinel, F- and Ba-rich mica, and fluorapatite in addition to clinopyroxene and nepheline. Distinct mineral assemblages, crystallization trends, and various xenocrysts indicate different melt sources, a varying extent of enrichment, retention, and loss of volatiles (including timing of H2O and CO2 saturation), and limited wall rock interaction for the two rock groups. Partly resorbed, Fo-depleted olivine cores in the younger rocks and green-core pyroxenes in the older ones suggest early magma mixing. The nephelinitic–basanitic magmas derived from up to 6% partial melting of amphibole-bearing garnet/spinel lherzolite at or just above the lithosphere–asthenosphere boundary. This source was metasomatized involving hydrous melts or fluids. On the other hand, the melilite-bearing rocks probably originated in the upper asthenosphere by less than 3.5% partial melting of amphibole ± phlogopite-bearing garnet wehrlite, previously generated by subduction-related metasomatism with high CaO/MgO and CO2/(CO2 + H2O) ratios. Infiltration and storage of the metasomatic agents occurred in the former lower lithosphere, following continuous recycling of oceanic crust, comprising the release of Ca, CO2, H2O, further volatiles, and incompatible elements. Both volcanic episodes coincide with topographic uplift, erosion, rifting, and reactivation of lithosphere-scale faults, probably related to phases of strong mechanical coupling between Alpine orogen and European foreland. The first period overlapped with an era of prolonged N-directed intraplate compressional stress due to the Adriatic-Eurasian collision, provoking large-scale deformation, isostatic compensation, erosion, and consequent lithosphere thinning in the future CEVP. The second period is associated with the Oligocene–Miocene main stage of the European Cenozoic Rift System. Onset of volcanism was accompanied by a change in deformation in the Upper Rhine Graben from (W)NW extension to (E)NE extension and transtension by a complex interplay of evasive movements responding to shortening in Alps and Jura. Magma compositions, barely magmatic graben structures, volcanic activity outside rifts, and extensive exhumation suggest that in response to rifting, passive asthenospheric doming also contributed to magmatism by causing strong lithosphere–asthenosphere interaction and providing heat. [ABSTRACT FROM AUTHOR]

The Neoproterozoic pyroxene gabbros and gabbronorites in the El-Baroud mafic intrusion in the Northern Eastern Desert (NED) of Egypt host Fe-Ti oxide ore deposits. This study discusses the major and trace elements of both titaniferous iron ores and their host rocks, along with the mineral chemistry (major and in situ trace elements) of interstitial clinopyroxene (Cpx), to gain a deeper understanding of the Fe-Ti oxide genesis. These ores occur as disseminated (55–60 vol.% of Fe-Ti oxides) and massive types (85–95 vol.%) in the form of the dyke, layer, and lens. They are composed of titanomagnetite (80–87 vol.%) with subordinate ilmenite (10–15 vol.%) and magnetite (3–5 vol.%), in accordance with their high Fe2O3 (75.66 wt.% on average) and TiO2 contents (16.30–17.60 wt.%). The Cpx in the investigated ores is diopside composition (Mg#; 0.72–0.83) and exhibits a nearly convex upward REE pattern, similar to Cpxs in the ferropicrite that originated from the primitive mantle. Melts in equilibrium with this Cpx resemble Greenstone ferropicrite melts; the parent melt of El-Baroud gabbros is possibly a ferropicritic melt that was derived from the lithospheric mantle during plume interaction. The El-Baroud gabbroic rocks were generated during the arc rifting and crystallized under a high oxygen fugacity at a temperature of 800–1000 °C and a pressure of 3 kbar with a depth of 12 km. The Fe-Ti oxide ores have been formed from ferropicritic parent melts by two processes, including in situ crystallization that leads to the formation of disseminated Fe-Ti oxides in the iron-rich gabbros at the bottom and liquid immiscibility that is responsible for the formation of thick Fe-Ti ore lenses and layers at the top of the gabbroic intrusion. Initially, titanomagnetite crystallized from the primary Ti-rich oxide melt. As cooling progressed, some of the excess titanium in this melt was exsolved in the form of the exsolution ilmenite lamellae within the titanomagnetite. The Fe-Ti oxide layers in the NED follow the trend of NW-SE (Najd trend), where their distribution is possibly controlled by the composition of parent melts (rich in Ti and Fe), high oxygen fugacity, and the structure related to the Najd fault system. The distribution of Fe-Ti oxide ores increases from the NED to the Southern Eastern Desert (SED), suggesting the dominant mantle plumes and/or shear zones in the SED relative to the NED. [ABSTRACT FROM AUTHOR]

The Shasatpich area hosts an ophiolitic complex located in the south of Kerman, southeast Iran. This ophiolitic complex is composed of lherzolite, harzburgite, and dunite. Olivine is one of the important minerals found in these rocks, which is observed along with pyroxene (orthopyroxene and clinopyroxene) and spinel. The combined range of olivines is forsterite to chrysolite, range of 84 to 92%. NiO with an average amount of about 0.38 wt% and MnO with an average of 0.14 wt% in olivines show the range has related to abyssal peridotites. In addition to serpentinization as a general alteration in the ultramafic rocks, petrographic studies show that evidence of metamorphism in the olivines of some harzburgites along with recrystallized antigorite crystals, which indicate a phase of thermal metamorphism in this harzburgite. These results have been confirmed in mineral chemistry studies too. Metamorphic olivines have an abnormality compared to magmatic olivines with a decrease in CaO. In chemical mineralogical studies, the amounts of forsterite and olivines show a regular increase from lherzolite to harzburgite and dunite. Raman spectroscopy studies on the studied olivines show the relationship between the peak shift of 854 waves/cm and forsterite values ​​of olivine minerals in the study area. [ABSTRACT FROM AUTHOR]

The Caledonian Yuechengling and western Dupangling granites,both located in the western Nanling Range of W-Sn-Cu metallogenic belt,but have different mineralizations.The Yuechengling biotite is mainly composed of iron biotite formed at a relatively low crystallization temperature(avg.,531℃)and high pressure(avg.,277 MPa),showing relatively poor features of magnesium(MgO 8.05%,XMg=0.39),but relatively rich in iron(FeOT 22.4%,IFe=0.61)and aluminum(Al2O316.8%),whereas the western Dupangling biotite is primary magnesium biotite formed at a higher crystallization temperature(avg.,687℃)and lower pressure(avg.,194 MPa),showing features of a relatively rich magnesium(MgO 11.9%,XMg=0.56),but poor in iron(FeOT 17.0%,IFe=0.45)and aluminum(Al2O315.5%).Together with petrography observations and the published whole rock data,it indicates that the Yuechengling granites are S-type granite,probably formed via partial melting of metapelites in the upper continental crust contaminated,and the western Dupangling granites are more like IS type granite formed via partial melting of crust-mantle mixed source.Further research indicates that the Yuechengling granites probably show magmatic features in favor of tungsten and a certain copper ore-forming,such as crust-source,lower oxygen fugacity(log f_(O2)=23.6),high fluorin(F 1.10%,IV(F)=1.62,IV(F/Cl)=6.00,log(f_(H2O)/fHF)fluid=4.78),high iron coefficient(XFe=0.58)and high magma fractionation(log(f_(H2O)/fHCl)fluid=5.10,log(fHF/fHCl)fluid=0.10),and the western Dupangling granites probably have characteristics of crustmantle mixed source,high oxygen fugacity(log f_(O2)=17.3),high chlorine(Cl 0.04%,log(fHF/fHCl)fluid=0.36),moderate iron coefficient(XFe=0.41)and low magmatic fractionation(log(f_(H2O)/fHCl)fluid=4.41,log(fHF/fHCl)fluid=0.36),which are only conducive for iron ore-forming in small scale.Therefore,petrogenesis and magmatic conditions may be the important factors restricting the metallogenetic ability of different types of metals in Yuechengling and western Dupanglingxi granites. [ABSTRACT FROM AUTHOR]

Skarn and Fe-Zn-Pb mineralization at the Wondong deposit located in the Taebaeksan Basin of the central-eastern region of Korean Peninsula occurs along the contact between the Upper Cretaceous quartz-feldspar porphyry (QFP) and carbonate rocks of the Ordovician Makgol Formation. The QFP is relatively fresh and has a sharp contact with the garnet skarn. Skarn is dominant in the carbonate rocks but is rare in the QFP. It consists almost of grandite throughout the skarn but has mineralogical zonation of proximal garnet, intermediate pyroxene, and distal wollastonite with increasing distance from the contact between the QFP and garnet skarn. Garnet becomes Fe-rich, and pyroxene tends to be enriched in Fe and Mn toward the marble front. Massive Fe mineralization, replacing garnet skarn, is restricted proximal to the QFP. In contrast, although the Zn-Pb mineralization is found in all areas it mostly occurs in the carbonate rocks beyond the skarn. Zinc-Pb mineralization occurred as stockwork and vein in the QFP and the garnet skarn consists of sphalerite, galena, Al-rich garnet, and calcite with a minor quantity of arsenopyrite. In contrast, the carbonate replacement of the Zn-Pb mineralization beyond skarn consists of sphalerite, pyrrhotite, galena, diopsidic pyroxene, and calcite with minor minerals such as arsenopyrite, löellingite, and chalcopyrite. Sphalerite, principal ore mineral, becomes darker and Fe- (up to 34.4 mol% FeS) and Mn-rich (up to 1.5 mol% MnS) with increasing distance from the QFP. Arsenopyrite is closely associated with sphalerite tends to be decreased in As away from the QFP. All sulfide minerals from Zn-Pb mineralization in the Wondong deposit have δ34S values ranging from 2.9 to 5.9‰, which are attributed to the magmatic source. In addition, the narrow range and subtle variation of the δ34S values for all sulfides throughout the Wondong deposits are not interpreted to be involved in the mixing of multiple sulfur sources. Geological, petrographic, mineralogical, and isotopic geochemical investigations show that the early skarn was formed in an environment of high fluid: rock ratios at the contact between the QFP and Makgol Formation and it was dominated by grandite, indicating the oxidizing nature of the skarn-forming fluids. The ore deposition began after the formation of the main garnet dominated skarn. The ore-forming fluids responsible for Zn-Pb mineralization are characterized by a less oxidizing nature, as defined by comparatively Al-enriched garnet in vein type mineralization in and around the QFP. Farther, the fluids producing the carbonate replacement of the Zn-Pb mineralization are unlikely to be engaged in external effects such as mixing with multiple sulfur sources even though it travels over long distance. [ABSTRACT FROM AUTHOR]

Textural, mineralogical and mineral compositional observations in a suite of Neoproterozoic aillikite and calcite kimberlite dykes from southern West Greenland point to consistent variations in melt major element compositions amongst these silica-undersaturated magma types. The aillikites have notably higher bulk SiO2/CO2, H2O/CO2 and K2O compared to calcite kimberlite. Bulk rock arrays, together with field and petrographic observations, emphasize that flow sorting of olivine and other crystalline phases during magma emplacement is important in controlling the compositions of individual samples from these ultramafic dykes. Flow sorting together with variable overall proportions of entrained lithospheric mantle material result in scatter on element–element plots, which makes the interpretation of regional scale major and trace element geochemical datasets difficult. We argue that a significant proportion of the regional Ni–MgO variation in the ultramafic dyke suite of SW Greenland is due to variation in the proportion of an entrained refractory lithospheric mantle component. Therefore, ratios of elements to MgO can be used as proxies for melt compositions. Ratios of SiO2, TiO2, Al2O3, FeO and K2O over MgO are systematically higher, and CO2/MgO lower, in aillikites compared to calcite kimberlites. The trace element patterns of the calcite kimberlite and aillikite dykes show strong similarities in incompatible element concentrations, resulting in overlapping ratios for the highly to moderately incompatible elements. However, differences in Zr-Hf concentrations between rock types imply differences in mantle source mineralogy. Guided by our observations, we present mixing models that demonstrate that partial flux-melting of phlogopite–ilmenite metasomes within the cratonic mantle lithosphere is capable of produce the geochemical characteristics of aillikites and mela-aillikites in West Greenland. Fusion of cratonic metasomes was initiated by infiltrating asthenosphere-derived carbonatitic melts previously identified as the parental liquids to calcite kimberlite. [ABSTRACT FROM AUTHOR]

During the Late Precambrian, the North Eastern Desert of Egypt underwent significant crustal evolution in a tectonic environment characterized by strong extension. The Neoproterozoic alkali feldspar granite found in the Homret El Gergab area is a part of the Arabian Nubian Shield and hosts significant rare metal mineralization, including thorite, uranothorite, columbite, zircon, monazite, and xenotime, as well as pyrite, rutile, and ilmenite. The geochemical characteristics of the investigated granite reveal highly fractionated peraluminous, calc–alkaline affinity, A-type granite, and post-collision geochemical signatures, which are emplaced under an extensional regime of within-plate environments. It has elevated concentrations of Rb, Zr, Ba, Y, Nb, Th, and U. The zircon saturation temperature ranges from 753 °C to 766 °C. The formation of alkali feldspar rare metal granite was affected by extreme fractionation and fluid interactions at shallow crustal levels. The continental crust underwent extension, causing the mantle and crust to rise, stretch, and become thinner. This process allows basaltic magma from the mantle to be injected into the continental crust. Heat and volatiles were transferred from these basaltic bodies to the lower continental crust. This process enriched and partially melted the materials in the lower crust. The intrusion of basaltic magma from the mantle into the lower crust led to the formation of A-type granite. [ABSTRACT FROM AUTHOR]

Bhilangana granitoid is a batholithic size body exposed in Bhilangana Valley and later thrusted over rocks of Lesser Himalaya. It comprises mylonitized porphyritic granite gneiss, psammitic gneiss, and its variants, containing primary biotite and muscovite, and S-type in nature. Bhilangana granitoid is intruded by basic intrusive. The variation in chemical signatures and associated petrogenetic issues of Bhilangana granitoid are dealt with detailed petrographic, geochemical and mineral chemical study. In the vicinity of basic intrusive, the porphyritic granite gneiss shows enrichment of MgO, whereas its evolved part, psammitic gneiss shows more boron enrichment with the presence of tourmaline nodules surrounded by quartzo-feldspathic rim. The major mineral assemblage in Bhilangana granitoid is quartz–K-feldspar–plagioclase–biotite–muscovite with tourmaline, epidote, zircon, ilmenite, apatite and monazite. The granite is peraluminous with ASI values always >1. Biotite shows variation from Fe-rich siderophyllitic to Mg-rich eastonitic composition, indicating involvement of both Al-rich crustal and Mg-rich mafic sources, inferring source heterogeneity or mixing of felsic-mafic magma. Granitoid melt was buffered below QFM to NNO and partly above HM, indicating a strong reducing to the oxidizing condition of melt. The melt was saturated with the presence of 3.3–6.8 wt.% H2O content. The crystallization temperature of Bhilangana granitoid (TZr) ranges between 697° and 807°C with a solidification pressure of about 2.92–4.31 kbar, implying crystallization at a depth of 8.76–13 km. The presence of greisens assemblage of quartz–mica–tourmaline–epidote, along with the presence of fluorite, is a representative greisens assemblage for Sn–W mineralization. Thus, the Bhilangana granitoid represents the fertile nature and potentiality of Sn–W minerals. Research highlights: Bhilangana granitoid is S-type, peraluminous granitoid, formed by anatexis of crustal material The biotite chemistry reveals the variation in the redox condition and modification in the oxidation state, preserved in the different variant of granite representing the magma mixing or source heterogeneity in protolith. The Bhilangana granitoid has attended the crystallization temperature (TZr) of 697–807 °C under pressure of about 2.92–4.31 kb implying the depth of crystallization of 8.76–13 km. The presence of greisenization favours the potential of Sn–W minerals. The geochemical results shows abnormal enrichment of W and Sn in the Bhilangana granitoid. The Bhilangana granitoid appears to have fertile nature for Sn–W mineral potential. [ABSTRACT FROM AUTHOR]

Rapakivi granite is characterized by its unique structure, which has important implications for tectonic settings, magmatic processes, and crust–mantle interactions. In this study, we conducted a combined analysis of the petrography, mineral chemistry, geochemistry, and zircon U–Pb dating and Lu–Hf isotopic compositions of the Niujiaoshan Early Paleozoic rapakivi-textured granite from the North Qinling Belt. Zircon U–Pb dating yielded a crystallization age of 447 ± 7 Ma, which is younger than the ultra-high-pressure (UHP) metamorphic age (~ 500 Ma) but similar to the granulite facies retrograde age (~ 450 Ma) of UHP eclogites and felsic gneisses in the North Qinling Belt. The rapakivi feldspar phenocrysts have ovoid K-feldspar cores, which are rich in mineral inclusions, such as amphibole, biotite, quartz, and plagioclase, indicating early crystallization. The ovoid K-feldspar cores are mantled by oligoclase, whreras the matrix comprises biotite, amphibole, and coarse-grained plagioclase. The amphibole and biotite in the granite are rich in Mg and are indicative of a crust–mantle origin. The εHf (t) values of the zircons range from − 2.04 to + 3.63, suggesting formation via crust–mantle interactions. The rapakivi-textured granite displays high-K meta-aluminous I-type granite affinity, with high SiO2, K2O, and Na2O contents. Based on the geological background and results of this study, we propose that the Niujiaoshan rapakivi-textured granite was formed via the mixing of crustal materials induced by upper mantle magma during the exhumation of the North Qinling UHP metamorphic terrane, which occurred in a post-orogenic setting. [ABSTRACT FROM AUTHOR]

Tourmaline is a valuable forensic mineral that contains a wide range of elemental components capable of reconstructing its geologic evolution. In this study, we developed detailed petrographic and geochemical research on tourmaline-bearing rocks and tourmalinites found surrounding the ca. 3.30 Ga rhyolite of the Gavião Block, northern São Francisco Craton. Two distinct types of mineral assemblages in the tourmaline-bearing rocks are recognized based on the presence of sulfides, oxide minerals, and carbonaceous matter. Along with these tourmaline-bearing rocks, tourmalinite samples are found. The mineral chemistry of tourmalines from the two types of tourmaline-bearing rocks reveals mainly schorl-dravite as tourmaline from a mineral assemblage containing quartz, tourmaline, pyrite, and hematite, and a diverse composition ranging from schorl-dravite, feruvite-uvite, and schorl-feruvite solid solutions for tourmalines present in the mineral assemblage that contains quartz, pyrite, and carbonaceous matter. The tourmaline composition is essentially foitite-schorl in tourmalinite samples. Most of the metasedimentary rocks studied have felsic and mafic source compositions. The interaction of hydrothermal fluid was crucial for the formation of sulfide and tourmaline minerals. However, distinct tourmaline origins are recognized in tourmaline-rich rocks, pointing out the relevance of sedimentary and metamorphic processes. [ABSTRACT FROM AUTHOR]

The studied Miocene volcanic rocks are observed in the Örenköy, Fındıkköy, and Kızılkaya Tepe regions in and around the Kütahya area. The Örenköy volcanic rocks consist of augite basalt, basaltic andesite and andesite, and show hyalo-microlitic porphyritic and cumulophyric texture, and contain plagioclase (An70-82Ab17-29Or1-2), clinopyroxene (Wo40-44En41-52Fs6-16), orthopyroxene (Wo1-4En64-71Fs27-34) olivine (Fo86-90) and Fe-Ti oxide. The Fındıkköy volcanic rocks include augite trachybasalt, augite basaltic trachyandesite and trachyandesite, and show hyalo-microlitic porphyritic and intersertal texture, and generally contain plagioclase (An58-88Ab12-38Or1-5), clinopyroxene (Wo44-48En38-47Fs8-17), olivine (Fo41-63) and Fe-Ti oxide, while the andesitic ones also contain biotite. The Kızılkaya Tepe volcanic rocks contain augite basalt, augite basaltic andesite and trachyandesite, and exhibit hyalomicrolitic porphyritic, vesicular, intersertal and trachytic texture, and include plagioclase (An53-85Ab14-44Or0-3), clinopyroxene (Wo39-46En41-52Fs8-16), orthopyroxene (Wo2-3En73-75Fs21-25), olivine (Fo52-82) and Fe-Ti oxide. In addition, the pre-eruptive crystallization conditions of the volcanic rocks were estimated using mineral chemistry analyses and thus it was determined that the magmas of the volcanic rocks have evolved by fractionation in magma chambers of the upper continental crust. [ABSTRACT FROM AUTHOR]

Attempts to geochemically distinguish between metamorphic-hydrothermal systems that form orogenic gold deposits and both reduced and oxidized magmatic-hydrothermal systems using isotopes or metal associations have proven ambiguous, particularly for orogenic gold and reduced intrusion-related gold systems. The absence of conclusive geochemical discriminators and the overlap in geologic characteristics have led to gold deposit models being potentially incorrectly applied, which in turn negatively affect regional mineral exploration and mine planning. In this study, in situ electron microprobe geochemical analyses of hydrothermal monazite and xenotime crystals associated with different types of gold-bearing deposits are shown to be effective geochemical discriminators. There are notable differences in mineral chemistry such as rare earth element (REE) profiles, total light REE, Dy, Er, Pr, Y, Nd/Sm, and La/Sm that distinguish monazite precipitated from metamorphic-hydrothermal fluids that form orogenic gold deposits and those precipitated from magmatic-hydrothermal fluids that form both porphyry Cu-Mo-Au and reduced intrusion-related gold deposits. Notable differences in overall xenotime abundances and concentrations of heavy REEs, Ca, and Sc are distinctive between the different deposit classes for xenotime. The origin of the controversially classified Pogo gold deposit, Tintina gold province, Alaska, which has been characterized as both a reduced intrusion-related and an orogenic gold deposit, is tested based upon the noted chemical differences associated with these hydrothermal phosphates. The findings of this study have implications for exploration and mine development in the Tintina gold province and other areas that contain deposits that are controversially classified as either orogenic or as magmatic-hydrothermal gold deposits. [ABSTRACT FROM AUTHOR]

We present a geochemical dataset and cathodoluminescence images of apatite from the Neoarchean (2610 Ma) glimmerite-carbonatite rocks from the Siilinjärvi complex, Eastern Finland. The subhedral, tapered prismatic grains are compositionally fluorapatite, with limited substitution of Ca by Sr, Na and low REE and Si contents. The Sr/Y ratios are among the highest in a global apatite comparison, comparable to those from other calcite carbonatites, dolomite carbonatites, and phoscorites. Some grains show evidence of late- or post-magmatic interaction with a carbonatite magma or a hydrothermal fluid, resulting in REE-rich overgrowth rims or recrystallized grains with abundant fluid inclusions. We interpret the high Sr/Y ratios combined with low REE contents and depleted heavy REE+Y to represent crystallization from a mantlederived carbonatite parental magma. We show that the Siilinjärvi apatite is chemically heterogeneous but with a limited range in compositions. There are noticeable compositional differences on all spatial scales from micrometer to tens of meters, i.e., within a single crystal, between crystals in a sample, between samples and the two individual sampling locations. We conclude that the intra-crystal geochemical variability in apatite is a suitable tracer of the magmatic and post-magmatic evolution of carbonatite complexes.

Introduction Mineral chemistry data as well as petrography provide a comprehensive picture of magma crystallization conditions that support the conclusions based on geochemical data. In addition, the chemical composition of minerals such as clinopyroxene, olivine, biotite, feldspar, and Fe-Ti oxides reflect physicochemical parameters (pressure, temperature, and oxygen fugacity), crystal growth history, and melt origin. The pressure, temperature and oxygen fugacity parameters are estimated from chemical data of various rock-forming minerals to provide information regarding the crystallization of magmas. The essential purposes of present study are to determine the physicochemical conditions (temperature and pressure), to identify the tectonic environment and to propose an emplacement model for Pargeh mafic magmas formation.Regional GeologyThe Pargeh area is a part of the Central Alborz Magmatic Belt (AMB) (Figure 1). There are extensive magmatic sections in this zone including the Cenozoic calc-alkaline and alkaline (potassic) magmatism generated in an arc and back-arc setting in an extensional environment (post collision). This belt is mainly composed of Upper Precambrian to Eocene sedimentary and volcanic sequences intruded by Mesozoic to Cenozoic plutons, in the central and western parts of the belt. The igneous rocks of the north and northeast of Qazvin were formed during three volcanic phases, of which only two phases can be seen in the study area. These Late Eocene-Oligo-Miocene plutonic rocks are related to post-collisional magmatic activities originated in back-arc extensional basins and have calc-alkaline to high-potassium shoshonitic characteristics. According to U–Pb dating, the age of the syenite and monzonite rocks is Late Eocene. But the exact age of the Pargeh gabbroic rocks is not known, considering that these intrusions were injected into Eocene tuffs, they are Late Eocene and possibly Oligocene.Analytical MethodsThe main minerals were analyzed by an electron microprobe at the Queen’s Facility for Isotope Research (QFIR), Queens University, Kingston, Canada. Operating conditions were as follows: the acceleration voltage was 15 kV, the beam current was 20 nA, and the diameter of the probe was 3 µm (Tables 1 to 6).PetrographyField and petrographic observation show that most of the Pargeh pluton is monzogabbro and olivine gabbros make up only a small part of the pluton. Olivine gabbro is a medium- to coarse-grained mesocratic-melanocratic rock. Olivine gabbro and monzogabbro are texturally varied. In both samples, intergranular, poikilitic, sub-ophitic and granular textures were identified. Olivine gabbro are dominated by olivine (20-25%vol), clinopyroxene (15-20 %vol), plagioclase (50-55 %vol), biotite (~ 5 %vol) and K-feldspar (~ 5 %vol). Accessory minerals include apatite and Fe-Ti oxides. Monzogabbros are characterized by a high proportion of plagioclase (55-60 %vol) and clinopyroxene (20-25 %vol), biotite (5-10%vol) and K-feldspar (8-10%vol).. Fe-Ti oxides and apatite are common accessory minerals in monzogabbros.DiscussionBased on research on the distribution of Ti in silicates and oxides of magmatic rocks, Verhoogen (1962) proposed that the crystallization temperature of clinopyroxene is positively correlated with its Ti content. Therefore, the higher clinopyroxene, crystallization temperature, the more Ti clinopyroxene likely to contain. The TiO2 content of clinopyroxenes in olivine gabbros is slightly higher than that of monzogabbros, pointing to the clinopyroxenes in olivine gabbro having a relatively higher crystallization temperature compared to that of clinopyroxenes in monzogabbro. In the 9-A and B diagram, all the samples are in the range of alkaline basalt, so the parental magma can be an alkaline magma. As mentioned above, clinopyroxenes have high amounts of Al and Ti, consistent with the evolution of an alkaline magma. High amounts of calcium in the studied clinopyroxenes indicate that the parental magma may have an alkaline nature. This tectonic setting discrimination diagram can distinguish basaltic clinopyroxenes from volcanic arc basalt (VAB), ocean floor basalt (OFB), intraplate tholeiite (WPT) and intraplate alkaline environments (WPA). In the F1-F2 tectonic environment discrimination diagram, all the study samples fall within the range of volcanic arc basalts (VAB+OFB), which shows that these rocks are probably formed in a volcanic arc and arc-related tectonic setting environment. In general, all tectonic discrimination diagrams based on clinopyroxene chemistry indicate an arc-related environment for the parental magma.ConclusionThe mafic rocks of Pargeh are composed of olivine gabbro and monzogabbro which are characterized by the presence of olivine, plagioclase, clinopyroxene, biotite and K-feldspar. The mineral chemistry results show the role of fractional crystallization as the main process in the formation of the parental magma of the rocks under study The chemical features of clinopyroxenes point that the parental magma must belong to a silica under-saturated alkaline series, characterized by high temperature, low pressure, low Si and high Ca contents possibly formed in a volcanic arc tectonic setting environment. As the xamined thermobarometers data show, the olivine gabbros generated at higher temperature and pressure than that of monzogabbros indicating that the olivine gabbros probably crystallized at a greater depth.

The Igla Ahmr region in the Central Eastern Desert (CED) of Egypt comprises mainly syenogranites and alkali feldspar granites, with a few tonalite xenoliths. The mineral potential maps were presented in order to convert the concentrations of total rare earth elements (REEs) and associated elements such as Zr, Nb, Ga, Y, Sc, Ta, Mo, U, and Th into mappable exploration criteria based on the line density, five alteration indices, random forest (RF) machine learning, and the weighted sum model (WSM). According to petrography and geochemical analysis, random forest (RF) gives the best result and represents new locations for rare metal mineralization compared with the WSM. The studied tonalites resemble I-type granites and were crystallized from mantle-derived magmas that were contaminated by crustal materials via assimilation, while the alkali feldspar granites and syenogranites are peraluminous A-type granites. The tonalites are the old phase and are considered a transitional stage from I-type to A-type, whereas the A-type granites have evolved from the I-type ones. Their calculated zircon saturation temperature TZr ranges from 717 °C to 820 °C at pressure < 4 kbar and depth < 14 km in relatively oxidized conditions. The A-type granites have high SiO2 (71.46–77.22 wt.%), high total alkali (up to 9 wt.%), Zr (up to 482 ppm), FeOt/(FeOt + MgO) ratios > 0.86, A/CNK ratios > 1, Al2O3 + CaO < 15 wt.%, and high ΣREEs (230 ppm), but low CaO and MgO and negative Eu anomalies (Eu/Eu* = 0.24–0.43). These chemical features resemble those of post-collisional rare metal A-type granites in the Arabian-Nubian Shield (ANS). The parent magma of these A-type granites was possibly derived from the partial melting of the I-type tonalitic protolith during lithospheric delamination, followed by severe fractional crystallization in the upper crust in the post-collisional setting. Their rare metal-bearing minerals, including zircon, apatite, titanite, and rutile, are of magmatic origin, while allanite, xenotime, parisite, and betafite are hydrothermal in origin. The rare metal mineralization in the Igla Ahmr granites is possibly attributed to: (1) essential components of both parental peraluminous melts and magmatic-emanated fluids that have caused metasomatism, leading to rare metal enrichment in the Igla Ahmr granites during the interaction between rocks and fluids, and (2) structural control of rare metals by the major NW–SE structures (Najd trend) and conjugate N–S and NE–SW faults, which all are channels for hydrothermal fluids that in turn have led to hydrothermal alteration. This explains why rare metal mineralization in granites is affected by hydrothermal alteration, including silicification, phyllic alteration, sericitization, kaolinitization, and chloritization. [ABSTRACT FROM AUTHOR]

Beryl mineralization in the Nugrus-Sikait domain in the South Eastern Desert (SED) of Egypt occurs as disseminated crystals in granitic pegmatite and quartz, as well as pegmatite veins crosscutting mélange schist and ophiolitic rocks. When granitic pegmatite comes into contact with the ophiolitic rocks, phlogopite and amphibole schists are formed due to K metasomatism. The ophiolitic mélange is intruded by leucogranite and related pegmatite along the NNW to NW Nugrus shear zone. Beryl samples have been collected from Um Sleimat, Madinat Nugrus, Wadi Abu Rusheid, and Wadi Sikait. Major oxides and in situ trace and rare earth elements (REEs) of beryl and associated minerals were analyzed through EPMA and LA-ICP-MS, respectively. The investigated beryl, based on its color and chemical compositions, can be classified into the two following types: pegmatitic beryl (type I) and schist-related beryl (type II). The former is colorless to pale green, and is mainly restricted in pegmatite veins; it is poor in Cr2O3 (up to 0.03 wt%) and MgO (Nil). The latter, deep green in color, is rich in Cr2O3 (up to 0.27 wt%) and MgO (up to 2.71 wt%), and occurs within quartz veins, phlogopite schists, and tremolite schists. The abundant beryl mineralization in phlogopite schists and their related quartz veins suggests that granite and associated pegmatite are the source rocks for the Be-bearing fluids that migrate along the NW-SE trending deep-seated tectonic zone, such as the Nugrus shear zone. Therefore, the formation of beryl in schists is attributed to the interaction of granitic/pegmatitic-derived Be-bearing fluids with serpentinite and gabbro interlayered with mélange schists. Variations in the trace and REE contents of both beryl types (I and II) indicate their two-stage formation from different compositions of Be-rich fluids, where light REEs, Zr, Nb, Ba, and Th decrease from type I beryl to type II. These two phases of beryl could be attributed to the magmatic/hydrothermal fluids associated with the pegmatite emplacement. The early phase of the late-stage magmatic-derived fluids was closely related to magma evolution and pegmatite formation, forming euhedral type I beryl. The late phase of pegmatite-derived fluids was mixed with serpentinite/schist-derived fluids that cause high V and Cr content in type II beryl. The composition of parent magmas of felsic rocks, the high degree of magma fractionation or the late stage melts, fluid compositions (rich in Be, Li, Cs, Rb, K), and alkali metasomatism, as well as the linear NW-SE trending deep-seated shear zone, are all factors possibly influencing beryl mineralization in the SED of Egypt. [ABSTRACT FROM AUTHOR]

Mineral chemistry data as well as petrography provide a comprehensive picture of magma crystallization conditions that support the conclusions based on geochemical data. In addition, the chemical composition of minerals such as clinopyroxene, olivine, biotite, feldspar, and Fe-Ti oxides reflect physicochemical parameters (pressure, temperature, and oxygen fugacity), crystal growth history, and melt origin. The pressure, temperature and oxygen fugacity parameters are estimated from chemical data of various rock-forming minerals to provide information regarding the crystallization of magmas. The essential purposes of present study are to determine the physicochemical conditions (temperature and pressure), to identify the tectonic environment and to propose an emplacement model for Pargeh mafic magmas formation. [ABSTRACT FROM AUTHOR]

Mantle xenoliths hosted in volcanic rocks from the island of Lutao offer a glimpse into the nature of the mantle beneath the northern Luzon volcanic arc. The xenoliths are spinel-bearing and composed mostly of harzburgite with one lherzolite and one olivine orthopyroxenite. The olivine (Fo92.5–88.9), orthopyroxene (Mg# = 94.6–89.2), and clinopyroxene (Wo49.1–38.1En57.0–45.4Fs3.0–11.0) compositions are similar to those of abyssal peridotites. The spinel compositions are variable and can be principally divided into high-Al (Cr# < 45) and low-Al (Cr# > 45) groupings. The whole rock compositions are similar to abyssal peridotite (Al2O3 = 0.95–2.07 wt %; Mg# = 88.5–90.9) and have U-shaped chondrite normalized rare earth element patterns. The Sr-Nd isotopes of the xenoliths are broadly chondritic (87Sr/86Sri = 0.704400–0.707908; εNd(t) = 0.0 − +1.5). The two-pyroxene equilibrium temperatures range from 900 to 1200 °C with the majority of temperature estimates >1000 °C. The olivine-orthopyroxene-spinel oxygen barometry estimates yielded ΔFMQ values from 0 to +2 and correspond to moderately oxidizing to oxidizing conditions. The xenoliths are likely derived from the Philippine Sea Plate lithospheric mantle that was modified by melt extraction and/or fluid enrichment processes. Trace element and isotopic mixing modeling indicate that 1–2% contamination by subducted South China Sea sediment can explain the Sr-Nd isotopic enrichment and Th and U elemental variability within the xenoliths assuming an initial composition similar to enriched depleted mid-ocean ridge mantle (E-DMM). The anomalously high two-pyroxene equilibrium temperatures of the Lutao xenoliths relative to other regions of the northern Luzon volcanic arc (Iraya <1000 °C) indicate that they were affected by a high-temperature event that was likely a consequence of recent intra-arc rifting that occurred after collision (<6 Ma) between the Luzon arc and the Eurasian margin. [ABSTRACT FROM AUTHOR]

Here, we present comprehensive electron probe micro analysis, laser Raman spectroscopic and X-ray diffraction (XRD) studies on the Mahadevpur H4/5 chondrite. The calculated full width at half maximum (FWHM) value of ~14-17 cm-1 for the Raman peaks in the Mahadevpur meteorite is in accordance with the shock stage of S4 with medium shock pressure regime of 30-35 GPa. The nanodiamonds were characterized with the observation of Raman peaks at 1333-1358 cm-1 and 1600 cm-1. The FWHM value of the Raman peaks reflects shock metamorphism in the meteorite. The XRD technique provides further independent validation of the nanodiamonds. [ABSTRACT FROM AUTHOR]

An integrated morphological and chemical analysis of Arctic aerosols was undertaken for Icelandic dust and Svalbard aerosols to be compared by scanning electron microscopy coupled with EDS microanalysis (SEM–EDS) via imaging and chemical analysis techniques. Results of the characterization of the particles from both surface sediments and suspended dust from desert areas in Iceland confirmed that volcanic glass is an excellent marker of Icelandic dust origin. Classification diagrams of particle chemical composition clearly distinguished the volcanic glass particles from the local surface sediments at Hornsund, Svalbard. In the same diagrams, a few particles were found in the aerosols from Hornsund which were morphologically and chemically similar to the Icelandic volcanic glass particles. Such properties, in principle, cannot be considered exclusive to volcanic glass. However, since Iceland is the largest and the most active source of long-range transported dust in the northern European high latitudes, and air mass trajectories reaching Hornsund did, actually, pass Iceland before the aerosol collection in the period under consideration, these particles likely originated in Iceland. On the other hand, the comparison with local and Icelandic sediments revealed the presence in the aerosols from Hornsund of particle types that cannot be attributed to either local or Icelandic dust. This observation highlights the possibility of extending and validating the application of the proposed geochemical criterion to different dust sources across the Arctic and the sub-Arctic, provided a consistent geochemical databank of representative dust sources from these areas is arranged. [ABSTRACT FROM AUTHOR]

The Ozren ophiolite complex (OOC) of the Dinaridic Ophiolite Belt is one of the six ophiolite complexes in Bosnia and Herzegovina. This paper deals with the mineral chemistry of amphiboles determined by electron probe micro-analysis and micro-Raman spectroscopy. The detected amphibole generations and types in mafic, ultramafic, and metamorphic rocks suggest a polystage evolution and are therefore useful petrogenetic indicators of the investigated OOC. Most gabbroic rocks and dolerites contain primary magmatic amphibole1 (magnesio-hornblende to pargasite, occasionally hastingsite) and prismatic to needle-like aggregates of late magmatic amphibole2 (magnesio-hornblende), while plagiogranite contains ferri-winchite and ferro-ferri-winchite as primary magmatic amphibole. Post-magmatic amphiboles were detected in dolerites, troctolites, and lesser in peridotites. The Na-(Ti)-rich amphibole3 (ferri-winchite and ferro-ferri-winchite to katophorite and ferri-katophorite) with amphibole4 (grunerite) rim formed along the grain boundaries of clinopyroxene, amphibole1, and plagioclase in dolerites. A part of these amphiboles grows into amphibole1, 2. Kaersutite to ferri-kaersutite, associated with phlogopite, occur in troctolites and dunites, while Mhbl was detected in harzburgite. The ultramafic rocks (lherzolites, harzburgites, and dunites) and the gabbroic layer are crosscut by clinopyroxene–plagioclase gabbroic and clinopyroxene–plagioclase–amphibole gabbro–dolerite dykes, suggesting 'dry' and 'hydrated' percolating melts generated in inferred subridge and supra-subduction settings, respectively. The amphibole3 and 4 in gabbros and dolerites and similar amphibole types in ultramafic rocks could be related to inferred arc-type basaltic and plagiogranitic percolating melts and fluids. Low-Al amphibole5 (tremolite and actinolite) and associated chlorite, albite, and clinozoisite represent the ocean-floor alterations in mafic rocks. Amphibole6 (magnesio-hornblende to pargasite) was identified in metamorphic sole amphibolites. Micro-Raman spectroscopy provided typical Raman spectra for the studied amphiboles, highlighting distinct features such as bands related to CMg content, CFe3+ presence, TO4 ring-breathing mode, TiO6 stretching mode, presence > 0.3 apfu of CTi, and TO4 stretching indicating CFe2+ in the structure. Applied amphibole geothermobarometry revealed the formation P–T conditions of amphibole (Amp)1 (avg. 863 °C at 0.23 GPa), Amp2 (avg. 747 °C at 0.17 GPa), Amp in the mantle rocks (avg. 853 °C at 0.64 GPa), Amp5 (avg. 349 °C at 0.03 GPa), and Amp6 (avg. 694 °C at 0.46 GPa). [ABSTRACT FROM AUTHOR]

The Asal–Ghoubbet Rift area comprises basaltic rocks with similar compositions that were formed by volcanic eruptions. To gain insight into the magmatic processes of these volcanic formations, we investigated the mineral chemistry of plagioclase macrocrysts and microcrysts found in the basaltic rocks by using an electron probe micro-analyzer (EPMA). These basaltic rocks contain olivine, pyroxene, euhedral plagioclase macrocrysts, and euhedral to subhedral plagioclase microcrysts. These plagioclase macrocrysts reach up to 4 cm in length in the form of giant crystals as plagioclase ultraphyric basalts (PUBs). They have a mineral composition varying from bytownite to labradorite with anorthite content ranging from An53 to An86. Also, the microcrysts of all these volcanic rocks are characterized by labradorite and andesine compositions with An22–80. According to the calculated plagioclase thermobarometry, the crystallization temperature of the plagioclase macrocrysts and microcrysts is 1082 to 1216 °C and 1072 to 1203 °C, respectively, and the pressure is 3.92 to 14.51 kbar for the macrocrysts and 2.99 to 14.84 kbar for the microcrysts. Based on these thermobarometry results for the plagioclases, we conclude that the volcanic formations located in the Asal–Ghoubbet area would have come from different eruptions from a single magmatic chamber. [ABSTRACT FROM AUTHOR]

Based on detrital monazite dating, mineral chemistry of tourmaline and rutile, bulk rock geochemistry, modal analysis of petrographic and palaeocurrent data, this study tracks the source of quartzose sandstone within the Cretaceous succession of the Cambay Basin primarily to rocks within the Aravalli‐Delhi Fold Belt. Monazite geochronology shows predominant peaks around 506 ± 11 Ma, 905 ± 12 Ma and a minor peak at 750 ± 20 Ma, 1485 ± 30 Ma relating sediment sources to the Aravalli‐Delhi orogeny and Pan‐African orogeny. The petrographic modal analysis of the moderate‐to‐well‐sorted Himmatnagar Sandstone indicates at least 91% quartz, with minor feldspar and rock fragments. The mineral chemistry of tourmalines in Himmatnagar Sandstone matches with Li‐ and Ca‐poor granitoid, pegmatites, metapelites and quartz tourmaline rocks. The trace element content of rutiles in sandstones corresponds to metapelitic sources. Detrital monazite dates and mineral chemistry of tourmalines and rutiles pinpoint the sediment source to the South Delhi Supergroup of rocks. The dominance of rounded zircons and tourmalines and abraded quartz overgrowth in the Himmatnagar Sandstone indicate the recycling of sediments, possibly from the Marwar Supergroup. Palaeoclimatic proxies based on mineralogy and geochemistry, particularly, the high value (93–97) of mineralogical index alteration, indicate intense chemical weathering of the source rocks under humid climatic conditions. Therefore, the combination of factors, including the quartzo‐feldspathic source rocks, intense chemical weathering under humid climatic conditions and the recycling of sediments facilitated the formation of quartzose sandstone within the Himmatngar Sandstone in the Cambay Basin. [ABSTRACT FROM AUTHOR]

Abstract The Cachoeirinha Sn ± (Nb-Ta) deposit is an important producer of the Rondônia Tin Province. It is inserted in the regional unit named Rondônia Intrusive Suite (995–956 Ma) and hosts granular accumulations of columbite group minerals (CGM) embedded in thick Cenozoic colluvial-alluvial covers. Cachoeirinha CGM have subrounded to angular grains, with irregular to regular internal zoning, micro-inclusion, and exsolution features. They have columbite-(Fe) as the dominant mineral phase, with variation in the Ta/(Ta+Nb) ratio and with Sn, Ti, W, U, Ba, Cr, REE, and V as chemical impurities. It has high total REE content (LREEN depleted, HREEN enriched, Ce and Eu anomalies), δ18O = 2.78‰, and with two U-Pb age groups: 1052 ± 6 and 909 ± 7 Ma. This information indicates that physicochemical oscillations favored the ionic substitutions and resorption mechanisms between Nb ↔ Ta, as well as coupled substitutions with the entry of geochemical impurities, according to the equation: 3(Sn, Ti, U, Si)4+ + (W, Cr)6+ ↔ 2(V, Nb, Ta)5+ + 2(Al, REE)3+ + (Fe, Mn, Ba)2+, at the temperature range between 400° and 500°C. Finally, the Cachoeirinha Sn ± (Nb-Ta) alluvial deposit host ore is related to at least two Neo-Mesoproterozoic magmatic pulses.

The Bundelkhand Craton (BuC) represents a significant Archean terrane within the northern Indian Craton and yet its tectono-metamorphic evolutionary history remains relatively understudied. Our investigation involves detailed petrography, geochemistry, and bulk composition modeling of both garnet-bearing and garnet-absent amphibolites with a two-fold objective: (i) to constrain the protolithic nature and tectonic settings involved in the genesis of these rocks, and (ii) to propose a tectono-metamorphic evolutionary history for the BuC. The BuC amphibolites originate from basalt and andesitic-basalt protoliths. Their trace element compositions reveal negative anomalies in Nb, Ta, and Ti, while their rare earth element (REE) normalized patterns indicate enrichment in light REEs over heavy REEs. The basaltic protolith is interpreted to have formed during orogeny in a compressional tectonic regime at the active margins of island arcs in a subduction-related setting. This interpretation is supported by various discrimination plots for amphibolites, such as Nb/Th vs Zr/Nb, Zr vs Zr/Y, and Th/Nb vs Ce/Nb, as well as high Th/Yb and low Nb/Yb contents— all of which suggest an island arc setting influenced by subduction. These amphibolites have undergone three distinct phases of metamorphism, as evidenced by petrography, mineral chemistry, and bulk composition modeling. This interpretation is further supported by geochemical discrimination diagrams which indicate that a subduction tectonic setting was active during peak metamorphism. During the pre-peak phase, the garnet-bearing amphibolites experienced pressure and temperature conditions ranging from 6.25 to 6.5 kbar and 580 to 590ºC, while the garnet-absent amphibolites underwent conditions from 5.0 to 5.8 kbar and 400 to 450ºC. Peak metamorphism was observed at pressures ranging from 6.8 to 7.4 kbar and temperatures from 760 to 805ºC for the garnet-bearing amphibolites, and at pressures from 7.0 to 7.4 kbar and temperatures from 785 to 810ºC for the garnet-absent amphibolites. The metamorphic retrograde conditions for the garnet-bearing amphibolites are defined by P-T conditions ranging from 4.45 to 4.75 kbar and 585 to 615ºC, while for the garnet-absent amphibolites, it ranges from 3.1 to 4.0 kbar and 620 to 710ºC. The mineral assemblages and P-T conditions delineate a clockwise P-T path for both, garnet-bearing and garnet-absent amphibolites from the Babina and Mauranipur regions. This suggests that the rocks underwent a burial process amid subduction tectonic settings in an arc-related environment, followed by a decompression stage that brought them to the surface.

This is an article in the field of earth sciences. To reveal the mineral chemistry characteristics and metamorphic temperature of garnet in the Liwu Group due to core of Jianglang dome, the major, trace and rare earth elements of garnet were analyzed at different locations in this paper. The results show that the major-element composition of garnet in schist from the Jianglang dome is mainly Alm. ICP-MS (average content 85.82%) and LA-ICP-MS (average content 83.51%) is basically consistent within the error range of the Alm content obtained.The total content of rare earth elements (REE) is high, and show obvious LREE-depleted and HREE-enriched left-declined REE distribution patterns, with unobvious Eu anomalies and negative Ce anomalies, Enriched in large ionic strength elements (U, Ta, Hf)and depleted high field lithophile elements (K, Sr, Ba). In addition, the formation temperature of garnet in schist from the Jianglang dome is 512～583 ℃, and the formed metamorphic pressure is relatively low. It is a negative correlation between the metamorphic temperature and the distance to the Xinhuoshan granite. In conclusion, the Jianglang dome experienced “Barrovian-type” metamorphism of high greenschist facies.

The Steel Mountain complex in western Newfoundland is one of several possible peri-Gondwanan basement slivers that have been emplaced along the northwestern margin of the Appalachian Orogen. The complex includes feldspathic anorthosite, gabbronorite, and magnetite-ilmenite ore. Megacrysts of plagioclase (andesine), orthopyroxene (hypersthene) and amphibole (hornblende) were analyzed by electron microprobe and they are of similar composition to the groundmass minerals. The ferromagnesian megacrysts have exsolution lamellae of Fe-Ti oxides, magnesio–hornblende, and clinopyroxene. The hornblende megacrysts and the lack of plagioclase in the exsolution lamellae are unusual for Proterozoic anorthosites and result from unusual abundance of water in the parental magma. Whole-rock Nd-Sm isotope determinations give an isochron age of ~1.2 Ga. Ar-Ar dating of biotite rims on hornblende shows an early Ordovician plateau age and the final heating step suggests a ~0.8 Ga age for the amphibole itself. Taken together with published zircon geochronology, these data suggest a provenance in the southern peri-Gondwanan Appalachians. [ABSTRACT FROM AUTHOR]

The Port Radium U-Cu-Ni-Co-Ag deposit in northwestern Canada is hosted within a mineral system that has generated a variety of mineralization styles from iron oxide-copper-gold to iron oxide-apatite, porphyry, skarn, and epithermal. Their genesis is linked to an extensive subduction-related magmatism that formed widespread dacite-rhyodacite-andesite volcanic and volcanoclastic sequences (~1.87 Ga), which have been intruded by their equivalent intrusive plutons. Pervasive and intensive hydrothermal alterations, including albitic, magnetite-actinolite-apatite, potassic ± albitic, phyllic, and propylitic occurred before the main sulfide, sulfarsenide, and uraninite vein-type mineralization. Although scarce sulfide minerals formed at the beginning of the hydrothermal activity, the main polymetallic arsenide-sulfarsenide-sulfide ± uraninite vein-type mineralization occurred during the epithermal stage. In addition to the common arsenides and sulfarsenides including nickeline, cobaltite, rammelsbergite, safflorite, skutterudite, gersdorffite, and arsenopyrite, three unique sulfarsenides were also found: Co0.67Ni0.32Fe0.02S0.19As2.80, which could be a sulfur-rich skutterudite, Ni0.85Co0.15S0.39As1.60, and Ni0.69Co0.31S0.47As1.52, which are chemically comparable to the Port Radium rammelsbergite with substantial addition of S and Co; they could be the solid solution product of gersdorffite-cobaltite or safflorite-rammelsbergite. [ABSTRACT FROM AUTHOR]

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Spinel is a precious stone with a long history. In ancient societies spinel was considered to be an imitation of ruby. With the depletion of ruby mineral resources, gem—grade spinel has attracted more and more attention from consumers. In the last decade, as the popularity of spinel in the global colored gem market continues to rise, plenty of domestic and foreign jewelry brands have launched spinel based jewelry. This study takes spinels from Burma, Vietnam, Sri Lanka, and Tanzania as its research objects and performs a series of tests to obtain their gemological characteristics, spectral characteristics, and chemical composition, with the aim of comparing the differences between spinels with different colors from different areas and exploring the chromogenic mechanism of spinels. Only Burmese red spinels have a typical Cr spectrum. The types of inclusions and the contents of trace elements are the main differences between spinels from the four areas. Burmese spinel is characterized by an octahedral negative crystal filled with dolomite or a mixture of dolomite and calcite. Magnesite is present in Sri Lankan spinels, and dolomite is present in Tanzanian spinel. Dislocation systems and the presence of titanite and talc inclusions are strongly indicative features of Vietnamese spinel. Sri Lankan spinel is characterized by abundant gas–liquid inclusions, such as the beaded healing fissure. The trace element contents of the four areas are different. Burmese spinel is poor in Fe and Zn (Fe: 135.68–3925 ppm; Zn: 338.58–1312 ppm), while Burmese red spinel is rich in Cr (up to 7387 ppm). Vietnamese spinel is rich in Fe (3669.63–19,425 ppm) and poor in Ti content (<89 ppm), while Tanzanian spinel is rich in Zn (5129.96–7008 ppm). High content of Cr + V can lead to the red color in spinel, and the contents of Cr and V change obviously with color. Spinels appear red when Cr content is higher than V, while spinels appear orange when V content is higher than Cr. The red, pink, and orange spinels are colored by Cr3+ and V3+, showing a wide absorption band centered at 400 nm and 550 nm. Fe plays a dominant role in purple spinels. The purple spinel is colored by Fe3+ and Fe2+. [ABSTRACT FROM AUTHOR]

Magnetite-(apatite) ore deposits are interpreted as being formed by the crystallization of iron-rich ultrabasic melts, dominantly generated by the interaction of silicate melts with oxidized P-F-SO4-bearing sedimentary rocks. This hypothesis is supported by geologic evidence, experimental studies, numerical modeling, stable and radiogenic isotope geochemistry, mineralogy, and melt- and mineral-inclusion data. Assimilation of crustal rocks during ascent promotes separation from a silicate magma of Fe-rich, Si-Al-poor melts with low solidus temperatures and viscosities, allowing coalescence, migration, and emplacement at deep to subaerial crustal environments. When the iron-rich melt attains neutral buoyancy, fractional crystallization leads to melt immiscibility similar to that observed in industrial blast furnaces, which promotes separation of massive magnetite ore overlain by different types of "slag" containing actinolite or diopside ± phosphates ± magnetite ± feldspar ± anhydrite ± scapolite, commonly enriched in high field strength elements. The mineralogy and morphology of this iron-depleted cap strongly depend on the depth of emplacement and composition of the iron-rich magma. Most of these systems exhibit high oxygen fugacity, which inhibits the precipitation of significant sulfide mineralization. The initially high fO2 of these systems also promotes the formation of low-Ti (< 1 wt%) magnetite: Ti acts as an incompatible component and is enriched in the iron-poor caps and in the hydrothermal aureole. High fluid-phase pressures produced during massive crystallization of magnetite from the melt further facilitate the exsolution of magmatic-hydrothermal fluids responsible for the formation of aureoles of alkali-calcic-iron alteration with hydrothermal replacement-style iron mineralization. On the whole, these systems are dramatically different from the magmatic-hydrothermal systems related to intermediate to felsic igneous rocks; they are more akin to carbonatite and other ultramafic rocks. [ABSTRACT FROM AUTHOR]

Objective The Fuxingtun deposit is a recently discovered large Ag-Pb-Zn polymetallic deposit in Horqin Right Wing Front area, Inner Mongolia. However, the researches on the deposit are very scarce. The study investigates occurrence characteristics of ore-forming elements, precipitation mechanism and genetic type of the deposit, in order to provide theoretical basis for the genesis of the deposit. Methods This study focused on sphalerite in different stages of the Fuxingtun Ag-Pb-Zn polymetallic deposit, and obtained metallography, major and trace elemental compositions of sphalerite, in order to discuss the precipitation mechanism of ore-forming elements and the genetic types of this deposit. Results Combined with field investigation and metallography observations, the metallogenic process of the Fuxingtun deposit can be divided into three stages: Cu-Zn sulfide stage (Stage Ⅰ), Pb-Zn sulfide stage (Stage Ⅱ) and Pb-Zn sulfide stage (Stage Ⅲ). The results of electron probe microanalysis show that the content of Fe in sphalerite varies greatly, and there is an obvious negative correlation between Fe and Zn. The results of LA-ICP-MS analysis showed that, the contents of Fe, Mn and In in sphalerite decreased gradually from Stage Ⅰ to Ⅲ, whereas those of Ga, Ge and Sb increased slightly. Based on the diagrams of laser ablation signal curve and the correlation among different elements, this study constrained that Fe, Mn, Cd, Cu In, and Ag in sphalerite are present as the form of isomorphism. On the other hand, Pb exists in the form of micro-inclusions, while Bi and Sb mainly occur as galena micro-inclusions in sphalerite. The trace element compositions of sphalerite grains also show that the periodic pressure fluctuation in the ore-forming process is responsible for the formation of oscillatory zone in sphalerite. We proposed that the multiple decompression and cooling of ore-forming fluids are the main mechanism of mineral precipitation in the Fuxingtun deposit. Conclusion Combined with the geological characteristics of the deposit and the trace element characteristics of sphalerite, it is proposed that the Fuxingtun Ag-Pb-Zn polymetallic deposit is a medium-sized, epithermal sulfide deposit.

Hercynite-rich spinel is a typical mineral of both quartz-bearing and quartz-free metapelitic rocks that form under low-pressure high-temperature conditions in the granulite facies (Sengupta et al., 1991) or upper-amphibolite facies of regional and contact metamorphism (Pattison and Tracy, 1991). Temperature-pressure estimation of metamorphic terrains is necessary to understand how large-scale crust evolution has occurred. High-temperature phase equilibrium cannot be properly evaluated solely based on normal cationic couple geothermobarometers, as ferromagnesian cationic exchange undergoes processes related to retrogression during cooling after peak metamorphism. Instead, key mineral parageneses are preserved and standard petrogenetic grids study based on reaction textures and mineral chemistry can be very helpful in better estimating temperature pressure.Regional GeologyDorbeh's contact aureole is formed in West Azerbaijan province, south of Urmia, north of Oshnavieh, and the Sanandaj-Sirjan zone around Dorbeh diorite. The intrusion is one of the components of the Urmia Plutonic Complex (UPC) which is spread along with granites and alkali syenites/granites at the northwest end of the Sanandaj-Sirjan zone in the south of Urmia. This diorite intruded sedimentary units of shale and carbonate belonging to Permian to Triassic-Jurassic including the Doroud and Ruteh Formations and have metamorphosed them in contact aureole, causing hornfels and calc-silicate to sometimes scarn deposits in the area (Modjarrad and Mohamed, 2015). This intrusion is covered by Miocene units (Ghalamghash, 2009). The observed parageneses in Dorbeh aureole including Cld + Chl, Ctd + And, Alm + Cld, And+Alm, Hc+Alm, Chl + Hc + And + Sil, Alm + And + Sil, Alm + And + Sil + Hc. The peak metamorphism assemblage is Alm + And + Sil + Hc. The reactions responsible for the parageneses productions were introduced in the previous studies (Modjarrad and Mohamed, 2015).Materials and Methods 50 microscopic thin sections were prepared and petrographically examined. A reagent sample with the highest number of parageneses and experienced peak metamorphism was analyzed by JEOL JXA-8200 microprobes electron device for garnet, chlorite, chloritoid, spinel, iron oxide, aluminosilicate, and apatite at the University of Potsdam, Germany. For whole rock chemistry, several metapelite samples were analyzed by XRF at the ALS-Chemex Laboratory of Canada.Discussion and ConclusionsThe main purpose of the present paper is to investigate the parageneses, the mineral chemistry, and the temperature-pressure estimation in the metamorphic contact aureole around Dorbeh intrusive. This intrusion consists of amphibole, plagioclase, and clinopyroxene, is a part of the Urmia Intrusive Complex (UPC), and with dioritic composition was intruded the Upper Cretaceous into the Paleozoic pelitic and limestone sedimentary rocks and metamorphosed them. The metapelite section of the aureole has exhibited interesting parageneses due to the exceptional iron-rich composition of the protolith. The hornfels part of the Dorbeh aureole is dominated by chlorite + chloritoid + garnet + aluminosilicates + spinel + opaque minerals and less quartz in the matrix. Mineral chemistry studies showed that Fe-chlorite between Repidolite to Bronswigite, Fe-chloritoid, Almandine garnet, Hercynitic spinel, and ilmenite are the minerals composition which is in agreement with the Fe-rich content of the parent rock. There was no specific zoning pattern in the metapelites garnet grains. It was also found that there is a reverse relationship between Si content and iron, magnesium, titanium, and chromium in chlorite and aluminosilicate structures. The metamorphic conditions for Dorbeh aureole by the multi-equilibria method by THERMOCALC software have been estimated at 570±7°C, at a pressure of 2.8±0.2 kbar.Detailed investigation of phase relationships of metamorphic rocks can be considered a desirable method along with quantitative data-based methods to evaluate the occurrence of progressive metamorphism. This method is based on direct observation of reaction textures and is more objective in estimating metamorphic conditions by the method of the intersection of equilibrium reactions. Most of the time, secondary cationic exchanges penetrate from the mineral boundary to a considerable stratum and question the accuracy of the temperature and pressure calculated on the cationic couple's geothermometers to a large extent. The contact aureole with higher than normal temperatures specific to the margins of dry mafic intrusives is sometimes associated with the formation of special parageneses such as Grt+Sil+And+Hc. This paragenesis has also been reported from high-temperature (granolithic) regional metamorphic terrains, but its production conditions are more limited in contact aureoles and require a high molar fraction of iron/aluminum or mass dryness and/or aureole. Therefore, the composition of all ferromagnesian minerals is very close to the final iron end member and no specific temperature fluctuation in the aureole is understood from the garnet zoning pattern. Although staurolite has not been seen in the studied sections, the evidence suggests that hercynite in the area was caused by staurolite breakdown. With precision in the composition of analyzed chlorites, it was found that there is a direct relationship between Si and alkaline content in chlorite structure, but titano-ferromagnesian content is in contrast with Si content. An almost similar relationship was observed in the aluminosilicate crystals. The inverse relationship between silica and Fe, Ti, and Cr oxides prevails.

The compositions (mineralogy, major- and trace-element chemistry of rocks and minerals, and Sr-Nd-Hf isotope systematics) of two kimberlite bodies, the Obnazhennaya pipe and the Velikan dyke from the Kuoika field, Yakutian kimberlite province (YaKP), which are close to each other (1 km distance) and of the same Upper Jurassic age, are presented. The kimberlites of the two bodies are contrastingly different in composition. The Obnazhennaya pipe is composed of pyroclastic kimberlite of high Mg and low Ti composition and is characterized by high saturation of clastic material of the lithospheric mantle (CMLM). The pyroclastic kimberlite contains rare inclusions of coherent kimberlite from previous intrusion phases. The Velikan dyke is represented by coherent kimberlite of relatively high Fe and high Ti composition, having neither mantle xenoliths nor olivine xenocrysts. The similarity of the isotopic geochemical characteristics for kimberlites from both bodies and their spatial and temporal proximity suggest that their formation is associated with the presence of a single primary magmatic source located in the asthenosphere. It is proposed that the asthenospheric melt differentiated into two parts: (1) a predominantly carbonate composition and (2) a carbonate–silicate composition, which, respectively, formed (a) low Fe and (b) Mg-Fe and high Fe-Ti petrochemical types of kimberlites. Both parts of the melt had different capabilities to capture the xenogenic material of the mantle rocks. The greater ability to destroy and, subsequently, capture CMLM belongs to the melt, which formed a high Mg type of kimberlite and which, according to the structural–textural classification, more often corresponds to the pyroclastic kimberlite. It is suggested that the primary kimberlite melt of asthenospheric origin is similar in composition to the high Fe, high Ti, coherent kimberlite from the Velikan dyke (in wt. %: SiO2–21.8, TiO2–3.5, Al2O3–4.0, FeO–10.6, MnO–0.19, MgO–21.0, CaO–17.2, Na2O–0.24, K2O–0.78, P2O5–0.99, CO2–12.6). It is concluded that the pyroclastic kimberlite contains only xenogenic Ol, whereas some of the Ol macrocrysts with high FeO content in the coherent kimberlite have crystallized from the melt. The similarity of Sr-Nd-Hf isotope systematics and trace element compositions for kimberlites of different ages (from Devonian to Upper Jurassic) in different parts of the YaKP (in the Kuoika, Daldyn and Mirny fields) indicates a single long-lived homogeneous magmatic asthenospheric source. [ABSTRACT FROM AUTHOR]