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Christina Yan Wang - One of the best experts on this subject based on the ideXlab platform.

  • cathodoluminescence images and trace element compositions of fluorapatite from the hongge Layered Intrusion in sw china a record of prolonged crystallization and overprinted fluid metasomatism
    American Mineralogist, 2017
    Co-Authors: Changming Xing, Christina Yan Wang
    Abstract:

    Cathodoluminescence (CL) and trace element analyses were performed for fluorapatite from the gabbro and Fe-Ti oxide ores in the upper zone of the Hongge Fe-Ti oxide-bearing, mafic-ultramafic Layered Intrusion in SW China. The fluorapatite is closely associated with Fe-Ti oxides and interstitial to plagioclase and clinopyroxene. The fluorapatite grains in one thin section vary from ~10 to 800 μm in width and ~50 to 1200 μm in length. Coarse-grained fluorapatite crystals (>200 in width) in the same thin section show both simple and complex CL images. The coarse-grained fluorapatite crystals with simple CL images show discontinuous, thin dark rims along grain boundaries, whereas those with complex images show clearly bright veinlets across the grains. On the other hand, fine-grained fluorapatite crystals (

  • magnetite rutile symplectite derived from ilmenite hematite solid solution in the xinjie fe ti oxide bearing mafic ultramafic Layered Intrusion sw china
    American Mineralogist, 2015
    Co-Authors: Christina Yan Wang, Changming Xing, Hongping He, Xiaoliang Liang, Huan Dong
    Abstract:

    A unique symplectitic intergrowth of magnetite + rutile is hosted by ilmenite in the gabbro of the Xinjie Fe-Ti oxide-bearing, mafic-ultramafic Layered Intrusion. The crystallization of rutile in the symplectite is probably formed by oxidation of ilmenite-hematite solid solution (Ilm-Hem ss ). Segregation of Fe 3+ in the Ilm-Hem ss at the rutile-host interfaces triggered the crystallization of magnetite along the margin of the growing rutile, and shaped the vermicular morphology of the rutile. The crystallization of magnetite can also locally release Ti 4+ to enhance the progressive growth and subsequent nucleation of rutile in the symplectite. The growth of the symplectite ceased when the temperature decreased to that of the miscibility gap of Ilm-Hem ss and Fe 3+ began to exsolve to form hematite lamellae in the ilmenite.

  • origin of the early permian wajilitag igneous complex and associated fe ti oxide mineralization in the tarim large igneous province nw china
    Journal of Asian Earth Sciences, 2014
    Co-Authors: Christina Yan Wang, Changming Xing, Yigang Xu
    Abstract:

    Abstract The Wajilitag igneous complex is part of the early Permian Tarim large igneous province in NW China, and is composed of a Layered mafic–ultramafic Intrusion and associated syenitic plutons. In order to better constrain its origin, and the conditions of associated Fe–Ti oxide mineralization, we carried out an integrated study of mineralogical, geochemical and Sr–Nd–Hf isotopic analyses on selected samples. The Wajilitag igneous rocks have an OIB-like compositional affinity, similar to the coeval mafic dykes in the Bachu region. The Layered Intrusion consists of olivine clinopyroxenite, coarse-grained clinopyroxenite, fine-grained clinopyroxenite and gabbro from the base upwards. Fe–Ti oxide ores are mainly hosted in fine-grained clinopyroxenite. Forsterite contents in olivines from the olivine clinopyroxenite range from 71 to 76 mol%, indicating crystallization from an evolved magma. Reconstructed composition of the parental magma of the Layered Intrusion is Fe–Ti-rich, similar to that of the Bachu mafic dykes. Syenite and quartz syenite plutons have eNd(t) values ranging from +1.4 to +2.9, identical to that for the Layered Intrusion. They may have formed by differentiation of underplated magmas at depth and subsequent fractional crystallization. Magnetites enclosed in olivines and clinopyroxenes have Cr2O3 contents higher than those interstitial to silicates in the Layered Intrusion. This suggests that the Cr-rich magnetite is an early crystallized phase, whereas interstitial magnetite may have accumulated from evolved Fe–Ti-rich melts that percolated through a crystal mush. Low V content in Cr-poor magnetite (

  • open magma chamber processes in the formation of the permian baima mafic ultramafic Layered Intrusion sw china
    Lithos, 2014
    Co-Authors: Pingping Liu, Changming Xing, Christina Yan Wang, Meifu Zhou, Jianfeng Gao
    Abstract:

    Abstract The Baima mafic–ultramafic Layered Intrusion of the 260-Ma Emeishan Large Igneous Province (ELIP) hosts the second largest Fe–Ti–(V) oxide deposit in the Panxi region, SW China. It is a ~ 1600-m-thick Layered body intruded by slightly younger syenitic and granitic plutons. The Intrusion includes the Lower and Upper Zones. Troctolite and olivine pyroxenite of the Lower Zone contains conformable oxide ore layers, whereas the Upper Zone consists of olivine gabbro and gabbro with abundant apatite in the higher level. The crystallization order of the silicates in the Baima Intrusion is olivine → plagioclase → clinopyroxene. Fe–Ti oxides (titanomagnetite and ilmenite) crystallized after olivine, and possibly plagioclase. The oxide ores in the Lower Zone show slightly LREE enriched patterns with (La/Yb)N values between 2.0 and 6.4, and positive Eu anomalies (Eu/Eu⁎) of 1.0 to 2.7. In contrast, olivine gabbros in the Lower Zone display stronger LREE enrichments (La/YbN = 7.7–14.0) and positive Eu anomalies (Eu/Eu⁎ = 2.8–3.3). Gabbros in the Upper Zone have REE profiles characterized by intermediate LREE enrichments with (La/Yb)N values of 3.2 to 11.2 and positive Eu anomalies of 2.1 to 3.0. Primitive mantle-normalized trace element patterns are characterized by negative La–Ce, Th, Sm and positive Nb–Ta, Ba and Ti anomalies in oxide ores and negative Th–U, Zr–Hf and positive Ba, Sr and Ti anomalies in olivine gabbro and gabbro. Fo of olivine and An of plagioclase remain roughly constant from 0 to ~ 90 m in the Lower Zone, indicating that the magma chamber was continuously filled by compositionally similar magmas during the initial stage. Three magma replenishments occurred afterwards in the upper part of the Lower Zone and the Upper Zone based on compositional reversals of plagioclase, olivine and Sr isotope. Mass balance calculations show that the Baima parental magma can produce all oxide ores under closed system conditions. A wide range of An values of plagioclase within thin sections and disequilibrium Sr isotopic compositions of plagioclase both along the stratigraphic profile (87Sr/86Sri = 0.70312–0.70510) and within thin sections indicate convection and co-accumulation of cumulus plagioclase that had crystallized from different magmas. We propose that the ~ 1600m-thick Baima Intrusion formed in an open and isotopically heterogeneous magma chamber that was periodically recharged by compositionally similar or more primitive magmas. In each replenishment cycle, the magma underwent progressive crustal contamination and fractional crystallization. Convection and sorting of crystals based on density differences result in igneous layering characterized by intervals of oxide ores, troctolite and olivine gabbro.

  • textures and mineral compositions of the xinjie Layered Intrusion sw china implications for the origin of magnetite and fractionation process of fe ti rich basaltic magmas
    Geoscience frontiers, 2013
    Co-Authors: Huan Dong, Changming Xing, Christina Yan Wang
    Abstract:

    Abstract The Xinjie Layered Intrusion in the Panxi region, SW China, hosts both Fe-Ti oxide and platinum-group element (PGE) sulfide mineralization. The Intrusion can be divided, from the base upward, into Units I, II and III, in terms of mineral assemblages. Units I and II are mainly composed of wehrlite and clinopyroxenite, whereas Unit III is mainly composed of gabbro. PGE sulfide-rich layers mainly occur in Unit I, whereas thick Fe-Ti oxide-rich layers mainly occur in Unit III. An ilmenite-rich layer occurs at the top of Unit I. Fe-Ti oxides include magnetite and ilmenite. Small amounts of cumulus and intercumulus magnetite occur in Units I and II. Cumulus magnetite grains are commonly euhedral and enclosed within olivine and clinopyroxene. They have high Cr 2 O 3 contents ranging from 6.02 to 22.5 wt.%, indicating that they are likely an early crystallized phase from magmas. Intercumulus magnetite that usually displays ilmenite exsolution occupies the interstices between cumulus olivine crystals and coexists with interstitial clinopyroxene and plagioclase. Intercumulus magnetite has Cr 2 O 3 ranging from 1.65 to 6.18 wt.%, lower than cumulus magnetite. The intercumulus magnetite may have crystallized from the trapped liquid. Large amounts of magnetite in Unit III contains Cr 2 O 3 ( 2 , 26.9 wt.% of FeO t , 8.2 wt.% of TiO 2 , 13.2 wt.% of CaO, 8.3 wt.% of MgO, 5.5 wt.% of Al 2 O 3 and 1.0 wt.% of P 2 O 5 . The composition is comparable with the Fe-rich melts in the Skaergaard and Sept Iles Intrusions. Paired non-reactive microstructures, granophyre pockets and ilmenite-rich intergrowths, are representative of Si-rich melt and Fe-Ti-rich melt, and are the direct evidence for the existence of an immiscible Fe-Ti-rich melt that formed from an evolved ferro-basaltic magma.

Bernard Charlier - One of the best experts on this subject based on the ideXlab platform.

  • diffusion driven chromium isotope fractionation in ultramafic cumulate minerals elemental and isotopic evidence from the stillwater complex
    Geochimica et Cosmochimica Acta, 2019
    Co-Authors: Yang Bai, Yan Xiao, Chen Chen, Mengmeng Cui, Liping Qin, Bernard Charlier
    Abstract:

    Abstract To investigate chromium diffusion kinetics in ultramafic cumulate minerals, we analyzed the Cr elemental and isotopic compositions of olivine, orthopyroxene, and chromite from the Stillwater Layered Intrusion. Core-to-rim compositional profiles reveal that Cr elemental concentrations decrease from 60 to 20 ppm in olivine and from 5000–4600 to 2700–2400 ppm in orthopyroxene. These zoned Cr distributions in olivine and orthopyroxene suggest that Cr was lost by diffusion into the melt. Olivine and orthopyroxene have δ53Cr values ranging from –0.09 to 0.25‰ and from –0.11 to 0.07‰, respectively, higher than the values of coexisting chromite (–0.23 to –0.07‰). This isotopic disequilibrium can be explained by diffusion-driven kinetic fractionation during cooling. The preferential diffusion of light Cr isotopes from silicate minerals to the melt resulted in isotopically heavier olivine and orthopyroxene, but the kinetic diffusion between chromite and melt negligibly affected the isotopic compositions of chromite grains due to their high Cr concentrations. Modeling results based on the observed Cr contents and isotopic compositions of silicate minerals constrain the cooling time of the Peridotite Zone in the Stillwater magmatic system to have been 10–100 kyr.

  • dual origin of fe ti p gabbros by immiscibility and fractional crystallization of evolved tholeiitic basalts in the sept iles Layered Intrusion
    Lithos, 2012
    Co-Authors: Olivier Namur, Bernard Charlier, M B Holness
    Abstract:

    We present a detailed study of two ca. 200 m-thick apatite-bearing ferrogabbro horizons of the Sept Iles Layered Intrusion (Canada). These rocks are the most evolved cumulates of the megacyclic units (MCU) I and II, and mark the transition between basaltic and silicic magmatism. They are made up of plagioclase (An55–34), olivine (Fo66–21), clinopyroxene (Mg#75–55), ilmenite, magnetite, apatite, ± pigeonite and are a significant source of Fe–Ti–P ore. Ferrogabbros have relatively uniform bulk-rock compositions in MCU I but are bimodal in MCU II. The liquid lines of descent for major elements in equilibrium with cumulates of MCU I and II have been calculated using a forward model formalism. Both trends evolve towards SiO2-enrichment and FeOt-depletion after saturation in Fe–Ti oxides. However, because of magma mixing in MCU II, they do not follow the same path. Evolved liquids from MCU II are shown to enter the experimentally-determined two liquid stability field, while MCU I liquids do not. Immiscibility in MCU II and its absence in MCU I are supported by the presence of contrasted reactive symplectites in cumulate rocks. Apatite-bearing ferrogabbros in MCU II have crystallized from distinct immiscible Fe-rich and Si-rich silicate melts which have physically segregated in the slow-cooling magma chamber. Two different types of cumulate rocks are thus produced: leucocratic and melanocratic gabbros. This is consistent with the presence of Si-rich and Fe-rich melt inclusions in apatite. In contrast, homogeneous ferrogabbros from MCU I were produced by simple fractional crystallization of a homogeneous liquid. Our data suggest that immiscibility could also explain the large geochemical variability of ferrogabbros in the Upper Zone of the Bushveld Complex (South Africa).

  • efficiency of compaction and compositional convection during mafic crystal mush solidification the sept iles Layered Intrusion canada
    Contributions to Mineralogy and Petrology, 2012
    Co-Authors: Olivier Namur, Bernard Charlier
    Abstract:

    Adcumulate formation in mafic Layered Intrusions is attributed either to gravity-driven compaction, which expels the intercumulus melt out of the crystal matrix, or to compositional convection, which maintains the intercumulus liquid at a constant composition through liquid exchange with the main magma body. These processes are length-scale and time-scale dependent, and application of experimentally derived theoretical formulations to magma chambers is not straightforward. New data from the Sept Iles Layered Intrusion are presented and constrain the relative efficiency of these processes during solidification of the mafic crystal mush. Troctolites with meso- to ortho-cumulate texture are stratigraphically followed by Fe–Ti oxide-bearing gabbros with adcumulate texture. Calculations of intercumulus liquid fractions based on whole-rock P, Zr, V and Cr contents and detailed plagioclase compositional profiles show that both compaction and compositional convection operate, but their efficiency changes with liquid differentiation. Before saturation of Fe–Ti oxides in the intercumulus liquid, convection is not active due to the stable liquid density distribution within the crystal mush. At this stage, compaction and minor intercumulus liquid crystallization reduce the porosity to 30%. The velocity of liquid expulsion is then too slow compared with the rate of crystal accumulation. Compositional convection starts at Fe–Ti oxide-saturation in the pore melt due to its decreasing density. This process occurs together with crystallization of the intercumulus melt until the residual porosity is less than 10%. Compositional convection is evidenced by external plagioclase rims buffered at An61 owing to continuous exchange between the intercumulus melt and the main liquid body. The change from a channel flow regime that dominates in troctolites to a porous flow regime in gabbros results from the increasing efficiency of compaction with differentiation due to higher density contrast between the cumulus crystal matrix and the equilibrium melts and to the bottom-up decreasing rate of crystal accumulation in the magma chamber.

  • anorthosite formation by plagioclase flotation in ferrobasalt and implications for the lunar crust
    Geochimica et Cosmochimica Acta, 2011
    Co-Authors: Olivier Namur, Bernard Charlier, Cassian Pirard, Joerg Hermann, Jeanpaul Liegeois, Jacqueline Vander Auwera
    Abstract:

    Abstract The Sept Iles Layered Intrusion (Quebec, Canada) is dominated by a basal Layered Series made up of troctolites and gabbros, and by anorthosites occurring (1) at the roof of the magma chamber (100–500 m-thick) and (2) as cm- to m-size blocks in gabbros of the Layered Series. Anorthosite rocks are made up of plagioclase, with minor clinopyroxene, olivine and Fe–Ti oxide minerals. Plagioclase displays a very restricted range of compositions for major elements (An 68 –An 60 ), trace elements (Sr: 1023–1071 ppm; Ba: 132–172 ppm) and Sr isotopic ratios ( 87 Sr/ 86 Sr i : 0.70356–0.70379). This compositional range is identical to that observed in troctolites, the most primitive cumulates of the Layered Series, whereas plagioclase in Layered gabbros is more evolved (An 60 –An 38 ). The origin of Sept Iles anorthosites has been investigated by calculating the density of plagioclase and that of the evolving melts. The density of the FeO-rich tholeiitic basalt parent magma first increased from 2.70 to 2.75 g/cm 3 during early fractionation of troctolites and then decreased continuously to 2.16 g/cm 3 with fractionation of Fe–Ti oxide-bearing gabbros. Plagioclase (An 69 –An 60 ) was initially positively buoyant and partly accumulated at the top of the magma chamber to form the roof anorthosite. With further differentiation, plagioclase ( 60 ) became negatively buoyant and anorthosite stopped forming. Blocks of anorthosite (autoliths) even fell downward to the basal cumulate pile. The presence of positively buoyant plagioclase in basal troctolites is explained by the low efficiency of plagioclase flotation due to crystallization at the floor and/or minor plagioclase nucleation within the main magma body. Dense mafic minerals of the roof anorthosite are shown to have crystallized from the interstitial liquid. The processes related to floating and sinking of plagioclase in a large and shallow Layered Intrusion serve as a proxy to refine the crystallization model of the lunar magma ocean and explain the vertically stratified structure of the lunar crust, with (gabbro-)noritic rocks at the base and anorthositic rocks at the top. We propose that the lunar crust mainly crystallized bottom-up. This basal crystallization formed a mafic lower crust that might have a geochemical signature similar to the magnesian-suite without KREEP contamination, while flotation of some plagioclase grains produced ferroan anorthosites in the upper crust.

  • differentiation of tholeiitic basalt to a type granite in the sept iles Layered Intrusion canada
    Journal of Petrology, 2011
    Co-Authors: Olivier Namur, Bernard Charlier, Jeanpaul Liegeois, M J Toplis, Michael D Higgins, Veronique Hounsell, Jacqueline Vander Auwera
    Abstract:

    The undeformed 564 Ma Sept Iles Layered Intrusion (Quebec, Canada) is a large igneous body of c. 20 000 km 3 . From the base to the top, it consists of a Layered Series dominated by troctolite and gabbro, an anorthositic Upper Border Series and a dominantly granitic Upper Series. The parent magma of the Layered Series is inferred to be an iron-rich tholeiitic basalt (48 wt % SiO 2 ; 15 wt % FeO t ). Whole-rock compositions from the chilled margin, dykes cross-cutting the Layered Series and silicic rocks from the Upper Series display continuous major and trace element geochemical trends ranging from basalts to ferroan metaluminous A-type granites (77 wt % SiO 2 ). Initial 143 Nd/ 144 Nd (0·51201–0·51207) and 87 Sr/ 86 Sr (0·70353–0·70548) indicate a juvenile-mantle source and minimal contamination by old crust (1–2%) during crystallization. Geochemical modeling, using the MELTS thermodynamic calculator combined with equations predicting mineral–melt equilibria from experiments on tholeiitic basalts, indicate that basaltic to monzonitic melt compositions are in equilibrium with the troctolites and gabbros of the Layered Series. Fe–Ti oxides saturate early in the Layered Series, after 14% fractionation of plagioclase–olivine cumulates. Further fractionation of Fe–Ti oxide-bearing gabbros drives the residual liquids toward silica enrichment and iron depletion. Major and trace element modeling indicates that the A-type granites from the Upper Series were produced by protracted fractional crystallization of an iron-rich basaltic parent magma, at a fraction of residual liquid of only 8%. The observed relative volumes of mafic cumulates and silicic rocks in the Intrusion are in agreement with the calculations. Most of the intermediate compositions correspond to magmatic mafic enclave-bearing granitoids and display geochemical evidence of hybridization. Intermediate compositions produced by fractional crystallization are scarce and a Daly gap occurs from 57 to 67 wt % SiO 2 . This gap could result either from the fractional crystallization process or from silicate–liquid immiscibility during that compositional interval.

Xie-yan Song - One of the best experts on this subject based on the ideXlab platform.

  • apatite geochemistry of the taihe Layered Intrusion sw china implications for the magmatic differentiation and the origin of apatite rich fe ti oxide ores
    Ore Geology Reviews, 2016
    Co-Authors: Xie-yan Song, Liemeng Chen, Yuwei She, Wenqin Zheng
    Abstract:

    Abstract The Taihe Intrusion is one of the Layered Intrusions situated in the central zone of the Emeishan Large Igneous Province (ELIP), SW China. The cyclic units in the Middle Zone of the Intrusion are composed of apatite-magnetite clinopyroxenite at the base and gabbro at the top. The apatite-rich oxide ores contain 6–12 modal% apatite and 20–50 modal% Fe-Ti oxides evidently distinguished from the coeval Intrusions in which apatite-rich rocks are poor in Fe-Ti oxides. Most of apatites of the Taihe Middle and Upper Zones are fluorapatite, although four samples show slightly high Cl content in apatite suggesting that they crystallize from a hydrous parental magma. Compared to the apatite from the gabbro of the Panzhihua Intrusion, situated 100 km to the south of the Taihe Intrusion, the apatite of the Taihe rocks is richer in Sr and depleted in HREE relative to LREE. The calculated magma in equilibrium with apatite of the Taihe Middle and Upper Zones also shows weakly negative Sr anomalies in primitive mantle normalized trace element diagrams. These features indicate that the apatite of the Taihe Middle and Upper Zones crystallizes after clinopyroxene and before plagioclase. The apatite of the Taihe Middle and Upper Zones shows weakly negative Eu anomalies suggesting a high oxygen fugacity condition. The high iron and titanium contents in the oxidizing magma result in crystallization of Fe-Ti oxides. Crystallization of abundant Fe-Ti oxides and clinopyroxenes lowers the solubility of phosphorus and elevates SiO2 concentration in the magma triggering the saturation of apatite. The positive correlations of Sr, V, total REE contents and Ce/Yb ratio in apatite with cumulus clinopyroxene demonstrate approximately compositional equilibrium between these phases suggesting they crystallized from the same ferrobasaltic magma. Early crystallization and accumulation of Fe-Ti oxide together with apatite produced the apatite-rich oxide ores at the base of the cyclic units of the Taihe Middle Zone.

  • variations of trace element concentration of magnetite and ilmenite from the taihe Layered Intrusion emeishan large igneous province sw china implications for magmatic fractionation and origin of fe ti v oxide ore deposits
    Journal of Asian Earth Sciences, 2015
    Co-Authors: Xie-yan Song, Songyue Yu, Hailong He
    Abstract:

    Abstract In situ LA–ICP–MS trace elemental analysis has been applied to magnetite and ilmenite of the Taihe Layered Intrusion, Emeishan large igneous province, SW China, in order to understand better fractionation processes of magma and origin of Fe–Ti–V oxide ore deposits. The periodic reversals in Mg, Ti, Mn in magnetite and Mg, Sc in ilmenite are found in the Middle Zone of the Intrusion and agree with fractionation trends as recorded by olivine (Fo), plagioclase (An) and clinopyroxene (Mg#) compositions. These suggest the Taihe Intrusion formed from open magma chamber processes in a magma conduit with multiple replenishments of more primitive magmas. The V and Cr of magnetite are well correlated with V and Cr of clinopyroxene indicating that they became liquidus phases almost simultaneously at an early stage of magma evolution. Ilmenite from the Middle and Upper Zones shows variable Cr, Ni, V, Mg, Nb, Ta and Sc contents indicating that ilmenite at some stratigraphic levels crystallized slightly earlier than magnetite and clinopyroxene. The early crystallization of magnetite and ilmenite is the result of the high FeOt and TiO2 contents in the parental magma. The ilmenite crystallization before magnetite in the Middle and Upper Zones can be attributed to higher TiO2 content of the magma due to the remelting of pre-existing ilmenite in a middle-level magma chamber. Compared to the coeval high-Ti basalts, the relatively low Zr, Hf, Nb and Ta contents in both magnetite and ilmenite throughout the Taihe Intrusion indicate that they crystallized from Fe–Ti–(P)-rich silicate magmas. Positive correlations of Ti with Mg, Mn, Sc and Zr of magnetite, and Zr with Sc, Hf and Nb of ilmenite also suggest that magnetite and ilmenite crystallized continuously from the homogeneous silicate magma rather than an immiscible Fe-rich melt. Therefore, frequent replenishments of Fe–Ti–(P)-rich silicate magma and gravitational sorting and settling are crucial for the formation the massive and apatite-rich disseminated ores in the Lower and Middle Zones of the Taihe Intrusion.

  • iron isotope fractionation during crystallization and sub solidus re equilibration constraints from the baima mafic Layered Intrusion sw china
    Chemical Geology, 2014
    Co-Authors: Xie-yan Song, Liemeng Chen, Xiangkun Zhu, Xiaoqi Zhang
    Abstract:

    Abstract To better understand Fe isotope fractionation between mafic minerals and oxides during crystallization of mafic magma and sub-solidus re-equilibration, the Fe isotopes of whole-rocks and separated minerals (olivine, clinopyroxene, magnetite and ilmenite) of the Baima mafic Layered Intrusion, SW China, have been investigated. The separated minerals show a systematical decrease in δ 57 Fe values, from magnetite (0.15 to 0.51‰) to olivine (− 0.11 to 0.15‰) and clinopyroxene (− 0.35 to 0.05‰) and then to ilmenite (− 0.82 to − 0.10‰), demonstrating regular fractionation between these minerals. Except for a few of samples, most of the olivine and clinopyroxene are similar to those of mantle xenoliths in Fe isotopes, indicating that Fe isotope equilibrium reached during magma crystallization was well preserved. By contrast, the Fe isotopes of the magnetite and ilmenite may be evidently modified by sub-solidus re-equilibration via the Fe 3 + versus Ti 4 + and Fe 2 + exchange between the oxides. Furthermore, the sub-solidus re-equilibration in Fe isotope is strongly controlled by the proportions of magnetite and ilmenite in rocks. Therefore, although the δ 57 Fe Ilm of the Lower Zone rocks with magnetite/ilmenite ratios as high as 6–10 was reduced evidently by the sub-solidus re-equilibration, the magnetite preserved their original Fe isotope compositions. By contrast, the Fe isotopes of both most magnetite and ilmenite in the Middle Zone had been markedly modified by sub-solidus re-equilibration owing to the moderate magnetite/ilmenite ratios (4–7). The decreases of both δ 57 Fe Mt and δ 57 Fe Ol upwards in the cyclic units of the Lower Zone reveal that extensive early fractional crystallization of the magnetite resulted in depletion of heavier Fe isotopes in the magma. On the other hand, early crystallization of olivine and clinopyroxene gave rise to the slight elevation of δ 57 Fe Ol values upwards in the cyclic units of the Middle and Upper zones. The stratigraphic reversals in the δ 57 Fe Mt and δ 57 Fe Ol values suggest multiple magma recharges. Additionally, the δ 57 Fe Ol values in the base of the Lower Zone (0.10 to 0.15‰) indicate that the parental magma were heavy in Fe isotope due to extensive silicate mineral fractionation at depth. This study indicates fractionation in Fe isotope between silicates and oxides during magma crystallization and sub-solidus re-equilibration.

  • key factors controlling the accumulation of the fe ti oxides in the hongge Layered Intrusion in the emeishan large igneous province sw china
    Ore Geology Reviews, 2014
    Co-Authors: Yan Luan, Xie-yan Song, Wenqin Zheng, Songyue Yu, Xiaoqi Zhang, Liemeng Chen, Xiaolin Tian
    Abstract:

    Abstract The Hongge Layered Intrusion hosts the largest Fe–Ti–V oxide ore deposit in the central part of the Emeishan Large Igneous Province, SW China. It is divided into Lower Zone (LZ), Middle Zone (MZ) and Upper Zone (UZ) from the bottom to the top. For the LZ, relatively higher Cr (250–3000 ppm) and Ni (50–200 ppm) contents of clinopyroxene, lower eNd259Ma and higher (87Sr/86Sr)259Ma values (− 2.82 to − 0.07 and 0.7057–0.7076, respectively) and plenty of hornblende demonstrate a more primitive parental hydrous magma. In contrast, relatively low Cr (

  • chalcophile element geochemistry of the baima Layered Intrusion emeishan large igneous province sw china implications for sulfur saturation history and genetic relationship with high ti basalts
    Contributions to Mineralogy and Petrology, 2013
    Co-Authors: Xiaoqi Zhang, Xie-yan Song, Liemeng Chen, Wei Xie, Yufeng Deng, Jiafei Zhang, Shuguang Gui
    Abstract:

    The Permian Baima mafic Layered Intrusion, believed to be related to the S-undersaturated Emeishan high-Ti basalts, hosts a giant Fe–Ti-V oxide deposit in the lower part of the Intrusion. Uniformly high Cu/Pd (1.9 × 106–6.1 × 104) and low Pd/Zr (<0.1) indicate that the Baima parental magma experienced prior sulfide segregation. Mantle-liked δ34S values and low S/Se values indicate negligible external sulfur addition. Primitive mantle-normalized PGE patterns and MELTS calculations indicate that extensive fractional crystallization (~59 %) of chromite, olivine and pyroxene at depth drove the primitive picritic magma to S saturation. Strong positive correlation between IPGE and PPGE and between PGE and V, Cr and S suggest that magmatic sulfide is the dominant mineral controlling the distribution of PGE in the Baima Intrusion. A positive correlation between S and Cr, FeOT + TiO2 and V content, together with MELTS calculations, indicate that the parental magma of the Baima Intrusion reached a second stage of S saturation in the shallower Baima magma chamber, which was likely triggered by decreasing Fe2+ accompanying magnetite precipitation. Primitive mantle-normalized PGE patterns for Baima Intrusion rocks display similar trends to high-Ti basalts inside the Panxi area, suggesting that they are comagmatic, and following a similar differentiation trend. However, the lavas erupted before they reached sulfide saturation. The more evolved nature of high-Ti basalts outside the Panxi area indicate that they experienced more extensive pre-eruption fractional crystallization. Further fractional crystallization process led these lavas show more PGE fractionated feature.

Liemeng Chen - One of the best experts on this subject based on the ideXlab platform.

  • apatite geochemistry of the taihe Layered Intrusion sw china implications for the magmatic differentiation and the origin of apatite rich fe ti oxide ores
    Ore Geology Reviews, 2016
    Co-Authors: Xie-yan Song, Liemeng Chen, Yuwei She, Wenqin Zheng
    Abstract:

    Abstract The Taihe Intrusion is one of the Layered Intrusions situated in the central zone of the Emeishan Large Igneous Province (ELIP), SW China. The cyclic units in the Middle Zone of the Intrusion are composed of apatite-magnetite clinopyroxenite at the base and gabbro at the top. The apatite-rich oxide ores contain 6–12 modal% apatite and 20–50 modal% Fe-Ti oxides evidently distinguished from the coeval Intrusions in which apatite-rich rocks are poor in Fe-Ti oxides. Most of apatites of the Taihe Middle and Upper Zones are fluorapatite, although four samples show slightly high Cl content in apatite suggesting that they crystallize from a hydrous parental magma. Compared to the apatite from the gabbro of the Panzhihua Intrusion, situated 100 km to the south of the Taihe Intrusion, the apatite of the Taihe rocks is richer in Sr and depleted in HREE relative to LREE. The calculated magma in equilibrium with apatite of the Taihe Middle and Upper Zones also shows weakly negative Sr anomalies in primitive mantle normalized trace element diagrams. These features indicate that the apatite of the Taihe Middle and Upper Zones crystallizes after clinopyroxene and before plagioclase. The apatite of the Taihe Middle and Upper Zones shows weakly negative Eu anomalies suggesting a high oxygen fugacity condition. The high iron and titanium contents in the oxidizing magma result in crystallization of Fe-Ti oxides. Crystallization of abundant Fe-Ti oxides and clinopyroxenes lowers the solubility of phosphorus and elevates SiO2 concentration in the magma triggering the saturation of apatite. The positive correlations of Sr, V, total REE contents and Ce/Yb ratio in apatite with cumulus clinopyroxene demonstrate approximately compositional equilibrium between these phases suggesting they crystallized from the same ferrobasaltic magma. Early crystallization and accumulation of Fe-Ti oxide together with apatite produced the apatite-rich oxide ores at the base of the cyclic units of the Taihe Middle Zone.

  • iron isotope fractionation during crystallization and sub solidus re equilibration constraints from the baima mafic Layered Intrusion sw china
    Chemical Geology, 2014
    Co-Authors: Xie-yan Song, Liemeng Chen, Xiangkun Zhu, Xiaoqi Zhang
    Abstract:

    Abstract To better understand Fe isotope fractionation between mafic minerals and oxides during crystallization of mafic magma and sub-solidus re-equilibration, the Fe isotopes of whole-rocks and separated minerals (olivine, clinopyroxene, magnetite and ilmenite) of the Baima mafic Layered Intrusion, SW China, have been investigated. The separated minerals show a systematical decrease in δ 57 Fe values, from magnetite (0.15 to 0.51‰) to olivine (− 0.11 to 0.15‰) and clinopyroxene (− 0.35 to 0.05‰) and then to ilmenite (− 0.82 to − 0.10‰), demonstrating regular fractionation between these minerals. Except for a few of samples, most of the olivine and clinopyroxene are similar to those of mantle xenoliths in Fe isotopes, indicating that Fe isotope equilibrium reached during magma crystallization was well preserved. By contrast, the Fe isotopes of the magnetite and ilmenite may be evidently modified by sub-solidus re-equilibration via the Fe 3 + versus Ti 4 + and Fe 2 + exchange between the oxides. Furthermore, the sub-solidus re-equilibration in Fe isotope is strongly controlled by the proportions of magnetite and ilmenite in rocks. Therefore, although the δ 57 Fe Ilm of the Lower Zone rocks with magnetite/ilmenite ratios as high as 6–10 was reduced evidently by the sub-solidus re-equilibration, the magnetite preserved their original Fe isotope compositions. By contrast, the Fe isotopes of both most magnetite and ilmenite in the Middle Zone had been markedly modified by sub-solidus re-equilibration owing to the moderate magnetite/ilmenite ratios (4–7). The decreases of both δ 57 Fe Mt and δ 57 Fe Ol upwards in the cyclic units of the Lower Zone reveal that extensive early fractional crystallization of the magnetite resulted in depletion of heavier Fe isotopes in the magma. On the other hand, early crystallization of olivine and clinopyroxene gave rise to the slight elevation of δ 57 Fe Ol values upwards in the cyclic units of the Middle and Upper zones. The stratigraphic reversals in the δ 57 Fe Mt and δ 57 Fe Ol values suggest multiple magma recharges. Additionally, the δ 57 Fe Ol values in the base of the Lower Zone (0.10 to 0.15‰) indicate that the parental magma were heavy in Fe isotope due to extensive silicate mineral fractionation at depth. This study indicates fractionation in Fe isotope between silicates and oxides during magma crystallization and sub-solidus re-equilibration.

  • key factors controlling the accumulation of the fe ti oxides in the hongge Layered Intrusion in the emeishan large igneous province sw china
    Ore Geology Reviews, 2014
    Co-Authors: Yan Luan, Xie-yan Song, Wenqin Zheng, Songyue Yu, Xiaoqi Zhang, Liemeng Chen, Xiaolin Tian
    Abstract:

    Abstract The Hongge Layered Intrusion hosts the largest Fe–Ti–V oxide ore deposit in the central part of the Emeishan Large Igneous Province, SW China. It is divided into Lower Zone (LZ), Middle Zone (MZ) and Upper Zone (UZ) from the bottom to the top. For the LZ, relatively higher Cr (250–3000 ppm) and Ni (50–200 ppm) contents of clinopyroxene, lower eNd259Ma and higher (87Sr/86Sr)259Ma values (− 2.82 to − 0.07 and 0.7057–0.7076, respectively) and plenty of hornblende demonstrate a more primitive parental hydrous magma. In contrast, relatively low Cr (

  • chalcophile element geochemistry of the baima Layered Intrusion emeishan large igneous province sw china implications for sulfur saturation history and genetic relationship with high ti basalts
    Contributions to Mineralogy and Petrology, 2013
    Co-Authors: Xiaoqi Zhang, Xie-yan Song, Liemeng Chen, Wei Xie, Yufeng Deng, Jiafei Zhang, Shuguang Gui
    Abstract:

    The Permian Baima mafic Layered Intrusion, believed to be related to the S-undersaturated Emeishan high-Ti basalts, hosts a giant Fe–Ti-V oxide deposit in the lower part of the Intrusion. Uniformly high Cu/Pd (1.9 × 106–6.1 × 104) and low Pd/Zr (<0.1) indicate that the Baima parental magma experienced prior sulfide segregation. Mantle-liked δ34S values and low S/Se values indicate negligible external sulfur addition. Primitive mantle-normalized PGE patterns and MELTS calculations indicate that extensive fractional crystallization (~59 %) of chromite, olivine and pyroxene at depth drove the primitive picritic magma to S saturation. Strong positive correlation between IPGE and PPGE and between PGE and V, Cr and S suggest that magmatic sulfide is the dominant mineral controlling the distribution of PGE in the Baima Intrusion. A positive correlation between S and Cr, FeOT + TiO2 and V content, together with MELTS calculations, indicate that the parental magma of the Baima Intrusion reached a second stage of S saturation in the shallower Baima magma chamber, which was likely triggered by decreasing Fe2+ accompanying magnetite precipitation. Primitive mantle-normalized PGE patterns for Baima Intrusion rocks display similar trends to high-Ti basalts inside the Panxi area, suggesting that they are comagmatic, and following a similar differentiation trend. However, the lavas erupted before they reached sulfide saturation. The more evolved nature of high-Ti basalts outside the Panxi area indicate that they experienced more extensive pre-eruption fractional crystallization. Further fractional crystallization process led these lavas show more PGE fractionated feature.

  • fractional crystallization and the formation of thick fe ti v oxide layers in the baima Layered Intrusion sw china
    Ore Geology Reviews, 2012
    Co-Authors: Xiaoqi Zhang, Xie-yan Song, Wenqin Zheng, Liemeng Chen, Wei Xie, Yufeng Deng, Jiafei Zhang, Shuguang Gui
    Abstract:

    Abstract The Baima Layered Intrusion is located in the central part of the Emeishan Large Igneous Province (ELIP). The N–S striking Intrusion is ~ 24 km long and ~ 2 km thick and dips to the west. Based on variations in modal proportions and cumulus mineral assemblages, the Intrusion from the base to the top is simply subdivided into a lower zone (LZ) with most of the economic magnetite layers, and an upper zone (UZ) with apatite-bearing troctolite and gabbro. The rock textures suggest crystallization of the Fe–Ti oxide slightly later than plagioclase (An67-54) but relatively earlier than olivine (Fo74-55), followed by clinopyroxene and finally apatite. Relatively low olivine forsterite content and abundant ilmenite exsolution lamellae in clinopyroxene indicate that the Baima parental magma is a highly evolved Fe–Ti-rich magma. Via MELTS model, it demonstrates that under a closed oxygen system, extensive silicate mineral fractionation of a picritic magma might lead to Fe and Ti enrichment and oxygen fugacity elevation in the residual magma. When such Fe–Ti-rich magma ascends to the shallower Baima Intrusion, the Fe–Ti oxides may become an early liquidus phase. Well-matched olivine and plagioclase microprobe data with the results of MELTS calculation, combined with relatively low CaO content in olivine (0.02–0.08 wt.%) indicate that wall-rock contamination probably plays a weak role on oxygen fugacity elevation and the early crystallization of Fe–Ti oxides. Several reversals in whole-rock chromium and plagioclase anorthite contents illustrate that multiple recharges of such Fe–Ti-rich magma mainly occurred along the lower part of the Baima magma chamber. Frequent Fe–Ti-rich magma replenishment and gravitational sorting and settling are crucial for the development of thick Fe–Ti oxide layers at the base of the Baima Layered Intrusion.

Xiaoqi Zhang - One of the best experts on this subject based on the ideXlab platform.

  • iron isotope fractionation during crystallization and sub solidus re equilibration constraints from the baima mafic Layered Intrusion sw china
    Chemical Geology, 2014
    Co-Authors: Xie-yan Song, Liemeng Chen, Xiangkun Zhu, Xiaoqi Zhang
    Abstract:

    Abstract To better understand Fe isotope fractionation between mafic minerals and oxides during crystallization of mafic magma and sub-solidus re-equilibration, the Fe isotopes of whole-rocks and separated minerals (olivine, clinopyroxene, magnetite and ilmenite) of the Baima mafic Layered Intrusion, SW China, have been investigated. The separated minerals show a systematical decrease in δ 57 Fe values, from magnetite (0.15 to 0.51‰) to olivine (− 0.11 to 0.15‰) and clinopyroxene (− 0.35 to 0.05‰) and then to ilmenite (− 0.82 to − 0.10‰), demonstrating regular fractionation between these minerals. Except for a few of samples, most of the olivine and clinopyroxene are similar to those of mantle xenoliths in Fe isotopes, indicating that Fe isotope equilibrium reached during magma crystallization was well preserved. By contrast, the Fe isotopes of the magnetite and ilmenite may be evidently modified by sub-solidus re-equilibration via the Fe 3 + versus Ti 4 + and Fe 2 + exchange between the oxides. Furthermore, the sub-solidus re-equilibration in Fe isotope is strongly controlled by the proportions of magnetite and ilmenite in rocks. Therefore, although the δ 57 Fe Ilm of the Lower Zone rocks with magnetite/ilmenite ratios as high as 6–10 was reduced evidently by the sub-solidus re-equilibration, the magnetite preserved their original Fe isotope compositions. By contrast, the Fe isotopes of both most magnetite and ilmenite in the Middle Zone had been markedly modified by sub-solidus re-equilibration owing to the moderate magnetite/ilmenite ratios (4–7). The decreases of both δ 57 Fe Mt and δ 57 Fe Ol upwards in the cyclic units of the Lower Zone reveal that extensive early fractional crystallization of the magnetite resulted in depletion of heavier Fe isotopes in the magma. On the other hand, early crystallization of olivine and clinopyroxene gave rise to the slight elevation of δ 57 Fe Ol values upwards in the cyclic units of the Middle and Upper zones. The stratigraphic reversals in the δ 57 Fe Mt and δ 57 Fe Ol values suggest multiple magma recharges. Additionally, the δ 57 Fe Ol values in the base of the Lower Zone (0.10 to 0.15‰) indicate that the parental magma were heavy in Fe isotope due to extensive silicate mineral fractionation at depth. This study indicates fractionation in Fe isotope between silicates and oxides during magma crystallization and sub-solidus re-equilibration.

  • key factors controlling the accumulation of the fe ti oxides in the hongge Layered Intrusion in the emeishan large igneous province sw china
    Ore Geology Reviews, 2014
    Co-Authors: Yan Luan, Xie-yan Song, Wenqin Zheng, Songyue Yu, Xiaoqi Zhang, Liemeng Chen, Xiaolin Tian
    Abstract:

    Abstract The Hongge Layered Intrusion hosts the largest Fe–Ti–V oxide ore deposit in the central part of the Emeishan Large Igneous Province, SW China. It is divided into Lower Zone (LZ), Middle Zone (MZ) and Upper Zone (UZ) from the bottom to the top. For the LZ, relatively higher Cr (250–3000 ppm) and Ni (50–200 ppm) contents of clinopyroxene, lower eNd259Ma and higher (87Sr/86Sr)259Ma values (− 2.82 to − 0.07 and 0.7057–0.7076, respectively) and plenty of hornblende demonstrate a more primitive parental hydrous magma. In contrast, relatively low Cr (

  • chalcophile element geochemistry of the baima Layered Intrusion emeishan large igneous province sw china implications for sulfur saturation history and genetic relationship with high ti basalts
    Contributions to Mineralogy and Petrology, 2013
    Co-Authors: Xiaoqi Zhang, Xie-yan Song, Liemeng Chen, Wei Xie, Yufeng Deng, Jiafei Zhang, Shuguang Gui
    Abstract:

    The Permian Baima mafic Layered Intrusion, believed to be related to the S-undersaturated Emeishan high-Ti basalts, hosts a giant Fe–Ti-V oxide deposit in the lower part of the Intrusion. Uniformly high Cu/Pd (1.9 × 106–6.1 × 104) and low Pd/Zr (<0.1) indicate that the Baima parental magma experienced prior sulfide segregation. Mantle-liked δ34S values and low S/Se values indicate negligible external sulfur addition. Primitive mantle-normalized PGE patterns and MELTS calculations indicate that extensive fractional crystallization (~59 %) of chromite, olivine and pyroxene at depth drove the primitive picritic magma to S saturation. Strong positive correlation between IPGE and PPGE and between PGE and V, Cr and S suggest that magmatic sulfide is the dominant mineral controlling the distribution of PGE in the Baima Intrusion. A positive correlation between S and Cr, FeOT + TiO2 and V content, together with MELTS calculations, indicate that the parental magma of the Baima Intrusion reached a second stage of S saturation in the shallower Baima magma chamber, which was likely triggered by decreasing Fe2+ accompanying magnetite precipitation. Primitive mantle-normalized PGE patterns for Baima Intrusion rocks display similar trends to high-Ti basalts inside the Panxi area, suggesting that they are comagmatic, and following a similar differentiation trend. However, the lavas erupted before they reached sulfide saturation. The more evolved nature of high-Ti basalts outside the Panxi area indicate that they experienced more extensive pre-eruption fractional crystallization. Further fractional crystallization process led these lavas show more PGE fractionated feature.

  • fractional crystallization and the formation of thick fe ti v oxide layers in the baima Layered Intrusion sw china
    Ore Geology Reviews, 2012
    Co-Authors: Xiaoqi Zhang, Xie-yan Song, Wenqin Zheng, Liemeng Chen, Wei Xie, Yufeng Deng, Jiafei Zhang, Shuguang Gui
    Abstract:

    Abstract The Baima Layered Intrusion is located in the central part of the Emeishan Large Igneous Province (ELIP). The N–S striking Intrusion is ~ 24 km long and ~ 2 km thick and dips to the west. Based on variations in modal proportions and cumulus mineral assemblages, the Intrusion from the base to the top is simply subdivided into a lower zone (LZ) with most of the economic magnetite layers, and an upper zone (UZ) with apatite-bearing troctolite and gabbro. The rock textures suggest crystallization of the Fe–Ti oxide slightly later than plagioclase (An67-54) but relatively earlier than olivine (Fo74-55), followed by clinopyroxene and finally apatite. Relatively low olivine forsterite content and abundant ilmenite exsolution lamellae in clinopyroxene indicate that the Baima parental magma is a highly evolved Fe–Ti-rich magma. Via MELTS model, it demonstrates that under a closed oxygen system, extensive silicate mineral fractionation of a picritic magma might lead to Fe and Ti enrichment and oxygen fugacity elevation in the residual magma. When such Fe–Ti-rich magma ascends to the shallower Baima Intrusion, the Fe–Ti oxides may become an early liquidus phase. Well-matched olivine and plagioclase microprobe data with the results of MELTS calculation, combined with relatively low CaO content in olivine (0.02–0.08 wt.%) indicate that wall-rock contamination probably plays a weak role on oxygen fugacity elevation and the early crystallization of Fe–Ti oxides. Several reversals in whole-rock chromium and plagioclase anorthite contents illustrate that multiple recharges of such Fe–Ti-rich magma mainly occurred along the lower part of the Baima magma chamber. Frequent Fe–Ti-rich magma replenishment and gravitational sorting and settling are crucial for the development of thick Fe–Ti oxide layers at the base of the Baima Layered Intrusion.