tong hou - Academia.edu (original) (raw)

Papers by tong hou

Research paper thumbnail of Petrogenesis of the Late Triassic Ultrapotassic Fanshan Fe-P Ore-bearing Complex in the North China Craton: Constraints on the Mineralization

Research paper thumbnail of A new clinopyroxene thermobarometer for mafic to intermediate magmatic systems

European Journal of Mineralogy

Clinopyroxene-only thermobarometry is one of the most practical tools to reconstruct crystallizat... more Clinopyroxene-only thermobarometry is one of the most practical tools to reconstruct crystallization pressures and temperatures of clinopyroxenes. Because it does not require any information of coexisting silicate melt or other co-crystallized mineral phases, it has been widely used to elucidate the physiochemical conditions of crystallizing magmas. However, previously calibrated clinopyroxene-only thermobarometers display low accuracy when being applied to mafic and intermediate magmatic systems. Hence, in this study, we present new empirical nonlinear barometric and thermometric models, which were formulated to improve the performance of clinopyroxene-only thermobarometry. Particularly, a total of 559 experimental runs conducted in the pressure range of 1 bar to 12 kbar have been used for calibration and validation of the new barometric and thermometric formulation. The superiority of our new models with respect to previous ones was confirmed by comparing their performance on 100 replications of calibration and validation, and the standard error of estimate (SEE) of the new barometer and thermometer are 1.66 kbar and 36.6 • C, respectively. Although our new barometer and thermometer fail to reproduce the entire test dataset, which has not been used for calibration and validation, they still perform well on clinopyroxenes crystallized from subalkaline basic to intermediate magmas (i.e., basaltic, basalt-andesitic, dacitic magma systems). Thus, their applicability should be limited to basaltic, basaltandesitic and dacitic magma systems. In a last step, we applied our new thermobarometer to several tholeiitic Icelandic eruptions and established magma storage conditions exhibiting a general consistency with phase equilibria experiments. Therefore, we propose that our new thermobarometer represents a powerful tool to reveal the crystallization conditions of clinopyroxene in mafic to intermediate magmas.

Research paper thumbnail of Experimental study on the effects of H2O upon crystallization in the Lower and Critical Zones of the Bushveld Complex with an emphasis on chromitite formation

Contributions to Mineralogy and Petrology

Research paper thumbnail of Geological settings and metallogenesis of high-grade iron deposits in China

Science China Earth Sciences

Research paper thumbnail of Geochemical Variation of Miocene Basalts within Shikoku Basin: Magma Source Compositions and Geodynamic Implications

Minerals

Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we r... more Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we report mineral compositions, major, trace-element, and Sr-Nd-Pb isotopic compositions of bulk-rocks from Sites C0012 (>18.9 Ma) and 1173 (13–15 Ma) of the Shikoku Basin. Samples from Sites C0012 and 1173 are tholeiitic in composition and display relative depletion in light rare earth elements (REEs) and enrichment in heavy REEs, generally similar to normal mid-ocean ridge basalts (N-MORB). Specifically, Site C0012 samples display more pronounced positive anomalies in Rb, Ba, K, Pb and Sr, and negative anomalies in Th, U, Nb, and Ta, as well as negative Nb relative to La and Th. Site 1173 basalts have relatively uniform Sr-Nd-Pb isotopic compositions, close to the end member of depleted mantle, while Site C0012 samples show slightly enriched Sr-Nd-Pb isotopic signature, indicating a possible involvement of enriched mantle 1 (EM1) and EM2 sources, which could be attributed to the metasom...

Research paper thumbnail of Mineralogical and Geochemical Study on the Yaojiazhuang Ultrapotassic Complex, North China Craton: Constraints on the Magmatic Differentiation Processes and Genesis of Apatite Ores

Frontiers in Earth Science

The differentiation process of ultrapotassic magmas is enigmatic and poorly understood. The Yaoji... more The differentiation process of ultrapotassic magmas is enigmatic and poorly understood. The Yaojiazhuang ultrapotassic complex is concentrically zoned by late-intruded syenite in the core and early emplaced clinopyroxenite in the periphery, combining a “bi-modal” lithology. Spatially, apatite and iron oxide-apatite (IOA) ores, glimmerite and pseudoleucite occur in the upper part of clinopyroxenite. The syenite and clinopyroxenite are composed of variable amounts of clinopyroxenite, biotite, K-feldspar, magnetite, apatite with minor analcite, titanite, and primary calcite. The pseudoleucite clinopyroxenite contains mainly clinopyroxene, biotite and garnet in the matrix, and nepheline–K-feldspar intergrowth with muscovite and minor celestine in the leucite pseudomorph. Geochemically, rocks of the Yaojiazhuang complex are significantly enriched in potassium (K), light rare earth elements (LREE), and large ion lithophile elements (LILE). Crustal contamination by Archean tonalite–trondhjemite–granodiorite (TTG) gneisses basement may play an important role to convert the syenitic melts from silica-undersaturation to saturation. Fractionation crystallization is supported by the mineral crystallization sequence to explain the bimodal lithologies instead of silicate liquid immiscibility. During the magmatic evolution, decompression, fractionation of volatile-poor clinopyroxene and the enhancement by CO2 may result in the exsolution of an aqueous fluid. The late-stage interactions between existing minerals and magmatic fluids in the crystal mush could be a key process in the generation of both leucite pseudomorphs and apatite/IOA ores.

Research paper thumbnail of Comparative geothermometry in high-Mg magmas from the Etendeka Province and constraints on their mantle source

Journal of Petrology

There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatur... more There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatures induced by thermal plumes or by other factors that enhance melt production from the mantle. A prerequisite for assessing the thermal plume model is a reliable estimate of liquidus temperatures of the magmas produced, preferably based on more than one method of geothermometry. The study reported here compares multiple geothermometers for the Etendeka LIP, which is among the largest Phanerozoic examples and one that shows several features suggestive of a plume origin (continental flood basalt province linked via an age-progressive volcanic ridge to an active hotspot). Magnesium (Mg)-rich magmas emplaced as dikes in NW Namibia are the most primitive rocks known from this province and are thus best suited to determine the composition and melting conditions of their mantle source. Earlier studies of the Etendeka Mg-rich dikes reported high liquidus temperatures based on olivine-melt Mg-Fe ...

Research paper thumbnail of Experimental evidence for a protracted enrichment of tungsten in evolving granitic melts: implications for scheelite mineralization

Research paper thumbnail of Phase equilibria and geochemical constraints on the petrogenesis of high-Ti picrite from the Paleogene East Greenland flood basalt province

Lithos

Abstract Phase equilibrium experiments have been performed on an extremely high-Ti (5.4 wt.% TiO2... more Abstract Phase equilibrium experiments have been performed on an extremely high-Ti (5.4 wt.% TiO2) picrite from the base of the Paleogene (~55 Ma) East Greenland Flood Basalt Province. This sample has a high CaO/Al2O3 ratio (1.14), a steep rare-earth elements (REE) profile, is enriched in incompatible trace elements, and is in chemical equilibrium with highly primitive olivine. This all suggests that the picrite is a near-primary melt that did not suffer major chemical evolution during ascent from the mantle source and through the crust. Near-liquidus phase relations were determined over the pressure range of 1 atm, 1 to 1.5 GPa and at temperatures from 1094 to 1400°C. They provide an important constraint on the petrogenesis of these lavas. The high-Ti picritic melt is multi-saturated with olivine (Ol) + orthopyroxene (Opx) at 1 GPa but has only Ol or Opx on the liquidus at lower and higher pressures, respectively. This indicates the primitive melt was last equilibrated with its mantle source at relatively shallow pressure (~ 1 GPa). Melting probably started at 2-3 GPa and the picritic melt was produced by 15-30% melting of the mantle source. Such a degree of partial melting requires a mantle with a high potential temperature (1480-1530˚C). The relatively low CaO content and high FeO/MnO ratios of the most primitive East Greenland picrites, the high Ni content of olivine phenocrysts and the presence of low-Ca pyroxene (i.e., pigeonite) at high pressure in our experiments all suggest that the mantle source contained a major component of garnet pyroxenite. Residual garnet in the source could adequately explain the low Al2O3 content (7.92 wt.%) and steep REE patterns of the picrite sample. However, simple melting of a lherzolitic source, even with a major pyroxenite component, cannot explain the formation of magmas with the very high Ti contents observed in some East Greenland basalts. We therefore propose that magmas highly-enriched in Ti were produced by melting of a metasomatized mantle source containing Ti-enriched amphibole and/or phlogopite.

Research paper thumbnail of New Insights for the Formation of Kiruna-Type Iron Deposits by Immiscible Hydrous Fe-P Melt and High-Temperature Hydrothermal Processes: Evidence from El Laco Deposit

Economic Geology

The world-renowned Pliocene El Laco iron deposit in northern Chile is the youngest and the best-p... more The world-renowned Pliocene El Laco iron deposit in northern Chile is the youngest and the best-preserved Kiruna-type deposit in the world. The genesis of the El Laco Kiruna-type iron deposit—i.e., whether it is magmatic or hydrothermal in origin—is a long-standing controversy. The interstitial Fe-P phase lined by early formed magnetite crystals observed in massive ores at El Laco is morphologically and geochemically consistent with that produced by recent immiscible experiments, confirming that the massive magnetite ores were products of complete solidification of an iron-rich mush comprising early crystallized magnetite and an interstitial immiscible Fe-P melt. The hydrothermal features in geochemistry of massive magnetite are similar to the features of magnetite in altered andesites, implying a superimposed hydrothermal process. The occurrence of melt inclusions with high homogenization temperatures (>700°C) hosted by the apatite in Cristales Grandes ores indicates that the veined ores formed shortly after the massive ores genetically related to the magmatic system. Some vesicles in the massive ores and the magnetite scoriae, previously interpreted as compelling evidence of volcanic structures, are demonstrated to be the residual pore spaces formed after interstitial phases between magnetite grains were removed by postmagmatic hydrothermal fluids and the accumulated debris eroded from massive ores with minor altered andesites, respectively. Thus, we propose a two-step genetic model in which massive ores resulted from magmatic processes and then were modified by subsequent magmatic-hydrothermal alteration. This model could be applied to the metallogenesis of most Kiruna-type iron deposits.

Research paper thumbnail of Immiscible hydrous Fe-Ca-P melt and the origin of iron oxide-apatite ore deposits

Nature communications, Apr 12, 2018

The origin of iron oxide-apatite deposits is controversial. Silicate liquid immiscibility and sep... more The origin of iron oxide-apatite deposits is controversial. Silicate liquid immiscibility and separation of an iron-rich melt has been invoked, but Fe-Ca-P-rich and Si-poor melts similar in composition to the ore have never been observed in natural or synthetic magmatic systems. Here we report experiments on intermediate magmas that develop liquid immiscibility at 100 MPa, 1000-1040 °C, and oxygen fugacity conditions (fO) of ∆FMQ = 0.5-3.3 (FMQ = fayalite-magnetite-quartz equilibrium). Some of the immiscible melts are highly enriched in iron and phosphorous ± calcium, and strongly depleted in silicon (<5 wt.% SiO). These Si-poor melts are in equilibrium with a rhyolitic conjugate and are produced under oxidized conditions (~FMQ + 3.3), high water activity (aHO ≥ 0.7), and in fluorine-bearing systems (1 wt.%). Our results show that increasing aHO and fO enlarges the two-liquid field thus allowing the Fe-Ca-P melt to separate easily from host silicic magma and produce iron oxide-ap...

Research paper thumbnail of Decoupling of Mg–C and Sr–Nd–O isotopes traces the role of recycled carbon in magnesiocarbonatites from the Tarim Large Igneous Province

Geochimica et Cosmochimica Acta

Research paper thumbnail of Geochemistry and oxygen isotope composition of magnetite from the Zhangmatun deposit, North China Craton: Implications for the magmatic-hydrothermal evolution of Cornwall-type iron mineralization

Ore Geology Reviews

Abstract The Zhangmatun deposit is a high-grade skarn-type iron deposit genetically linked with a... more Abstract The Zhangmatun deposit is a high-grade skarn-type iron deposit genetically linked with a gabbroic intrusion, and it has been recognized as a typical example of “Cornwall-type” deposits in China. Electron microprobe (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data on magnetite show decreasing contents of Ti, V, Cr, Mn, Co and Ga, from the gabbro, through the skarn, and to the iron ores. Additionally, magnetite grains from the gabbro, skarn and iron ores have similar primary mantle normalized signature and chondrite-normalized REE pattern, suggesting that the Fe in them might have be derived from a common source. The δ 18 O V-SMOW values of magnetite from iron ores mainly range from 4.3‰ to 6.4‰, markedly higher than that of magmatic magnetite (3.0‰). The significantly elevated oxygen isotopes of both magnetite and the corresponding water in the hydrothermal system are considered to reflect oxygen isotopic exchange between the ore-forming fluids and 18 O-rich carbonate rocks at relatively high temperature. Thus, the magnetite in the iron ores is inferred to be predominantly precipitated from the modified ore-forming fluids, rather than directly from the unreacted primary magmatic fluids. In the time-resolved analytical signals of LA-ICP-MS, the abnormal signals of incompatible elements such as Si, Ca and Mg are attributed to the sub-microscopic silicate mineral relicts. The inference is also supported by the BSE images and chemical maps of representative magnetite. The abnormal signals of Na and K are possibly related to the micro- to nano-scale salt-bearing fluid inclusions in magnetite. Based on the geochemical characteristics of different magnetite grains and varying FeO T in the fresh and altered gabbroic rocks, we propose that the iron in the ores was mainly derived from leaching of the solidified ore-related gabbro during the contact metasomatism by hydrothermal fluids. The interaction between hydrothermal fluids and carbonate country rocks and the evolution of the ore-forming fluids, including the changes in geochemical composition, decreasing temperature and pressure, and increasing oxygen fugacity, provided the conditions for precipitation of magnetite from ore-forming fluids. Our study has potential implications in understanding the origin of ‘Cornwall-type’ deposits elsewhere world.

Research paper thumbnail of Carboniferous porphyry Cu–Au deposits in the Almalyk orefield, Uzbekistan: the Sarycheku and Kalmakyr examples

International Geology Review

ABSTRACT The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is t... more ABSTRACT The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is the second largest porphyry region in Asia and hence has attracted considerable attention of the geologists. In this contribution, we report the zircon U–Pb ages, major and trace element geochemistry as well as Sr–Nd isotopic data for the ore-related porphyries of the Sarycheku and Kalmakyr deposits. The zircon U–Pb ages (Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)) of ore-bearing quartz monzonite and granodiorite porphyries from the Kalmakyr deposit are 326.1 ± 3.4 and 315.2 ± 2.8 Ma, and those for the ore-bearing granodiorite porphyries and monzonite dike from the Sarycheku deposit are 337.8 ± 3.1 and 313.2 ± 2.5 Ma, respectively. Together with the previous ages, they confine multi-phase intrusions from 337 to 306 Ma for the Almalyk ore cluster. Geochemically, all samples belong to shoshonitic series and are enriched in large-ion lithophile elements relative to high field strength elements with very low Nb/U weight ratios (0.83–2.56). They show initial (87Sr/86Sr)i ratios of 0.7059–0.7068 for Kalmakyr and 0.7067–0.7072 for Sarycheku and low εNd(t) values of −1.0 to −0.1 for Kalmakyr and −2.3 to 0.2 for Sarycheku, suggesting that the magmas were dominantly derived from a metasomatized mantle wedge modified by slab-derived fluids with the contribution of the continental crust by assimilation-fractional-crystallization process. Compared to the typical porphyry Cu deposits, the ore-bearing porphyries in the Almalyk cluster are shoshonitic instead of the calc-alkaline. Moreover, although the magmatic events were genetically related to a continental arc environment, the ore-bearing porphyries at Sarycheku and Kalmakyr do not show geochemical signatures of typical adakites as reflected in some giant porphyry deposits in the Circum-Pacific Ocean, indicating that slab-melting may not have been involved in their petrogenesis.

Research paper thumbnail of Petrogenesis of the Ultrapotassic Fanshan Intrusion in the North China Craton: Implications for Lithospheric Mantle Metasomatism and the Origin of Apatite Ores

Journal of Petrology

The Fanshan intrusion in the North China Craton (NCC) is concentrically zoned with syenite in the... more The Fanshan intrusion in the North China Craton (NCC) is concentrically zoned with syenite in the core (Unit 1), surrounded by ultramafic rocks (clinopyroxenite and biotite clinopyroxenite; Unit 2), and an outer rim of garnet-rich clinopyroxenite and orthoclase clinopyroxenite and syenite (Unit 3). The intrusive rocks are composed of variable amounts of Ca-rich augite, biotite, orthoclase, melanite, garnet, magnetite and apatite, with minor primary calcite. Monomineralic apatite rocks, nelsonite and glimmerite exclusively occur in Unit 2. Geochemically, the Fanshan rocks are highly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), moderately depleted in high field strength elements (HFSE), and have a limited range of Sr-Nd-O isotopic compositions. The similar mineralogy, mineral compositions, and trace element characteristics of the three units suggest that all the rocks are co-magmatic. The parental magma is ultrapotassic and is akin to kamafugite. Very low-degree partial melting of metasomatized lithospheric mantle best explains the geochemistry and petrogenesis of the parental magmas of the Fanshan intrusion. We propose that the mantle source may have been metasomatized by a hydrous carbonate-bearing melt, which has imprinted the enriched Sr-Nd isotopic signature and incompatible element enrichment with conspicuous negative Nb-Ta-Zr-Hf-Ti anomalies and LREE enrichments. The mantle source enrichment may be correlated with oceanic sediment recycling during southward subduction of the Paleo-Asian oceanic plate during the Carboniferous and Permian. We propose that crystal settling and mechanical sorting combined with repeated primitive magma replenishment and mixing with previously fractionated magma is the predominant process responsible for the formation of the apatite ores.

Research paper thumbnail of The origin of nelsonite constrained by melting experiment and melt inclusions in apatite: The Damiao anorthosite complex, North China Craton

Gondwana Research

Models for the nelsonite formation are currently highly contentious, with liquid immiscibility an... more Models for the nelsonite formation are currently highly contentious, with liquid immiscibility and fractional crystallisation as frequently proposed formation mechanisms. The nelsonites in the Damiao massif anorthosite complex in the North China Craton are revisited here together with experimental evidence for the existence of silica-free CaO-FeO-Fe 2 O 3-TiO 2-P 2 O 5 immiscible nelsonitic liquids. Our results of differential scanning calorimetry (DSC) and internally heated pressure vessel (IHPV) demonstrate that nelsonite with the composition of one-third apatite and two-thirds Fe-Ti oxides by weight 1) completely melts well above 1450 ºC at dry condition, which is in good agreement with numerous experimental studies of the CaO-P 2 O 5-Fe x O system for metallurgical purposes; 2) does not melt at the temperature up to 1200 ºC with presence of considerable amount of volatiles, e.g., fluorine and water. Therefore, the composition of the nelsonite cannot be molten at temperatures relevant for crystallisation of the Damiao magma. A review of experimental studies of liquid immiscibility and analyses of natural immiscible glasses show that all the liquids on the Fe-and P-rich side of the miscibility gap have at least 20 wt. % of aluminosilicate components. In addition, our new analyses of apatite-hosted melt inclusions in Damiao nelsonite provide a crucial clue for the nelsonite formation. The inclusions range from ~3 to 200 µm in diameter. They are ubiquitous and meet all the morphological criteria of primary melt inclusions crystallised into assemblages of daughter minerals. Almost all assemblages contain vermiculite and/or chlorite, and some contain biotite, amphibole, phlogopite and Fe-Ti oxide. Bulk compositions of analysed inclusions show large variations in SiO 2 (20.79-50.16 wt. %) and FeO t (13.44-32.78 wt. %). With a few exceptions, the inclusions are very low in CaO (0.04-1.51 wt. %) and high in Al 2 O 3 (10-21.17 wt. %). The re-homogenized inclusions at 1200ºC obtained by IHPV show similar compositional characteristics but incorporated excessive melting of the host apatite. Nevertheless, the compositions significantly differ from those of the typical immiscible Fe-rich melts despite the high Fe content and low silica. It appears that the cumulus apatite crystallised from Fe-rich, hydrated late-stage immiscible Fe-rich melt formed by liquid immiscibility occurred in the relatively early stage, i.e. prior to the arrival of aqueous fluid phase. We propose that the inclusions at Damiao record a trend of intercumulus melt evolution, which have been through liquid-liquid immiscibility but most likely have been strongly affected by separation of a hydrothermal fluid phase and the losses of alkali and Ca silicate components from the melt into the fluid.

Research paper thumbnail of Experimental confirmation of high-temperature silicate liquid immiscibility in multicomponent ferrobasaltic systems

American Mineralogist, 2015

Research paper thumbnail of Petrogenesis of nephelinites from the Tarim Large Igneous Province, NW China: Implications for mantle source characteristics and plume–lithosphere interaction

Lithos, 2015

ABSTRACT The nephelinite exposed in the Wajilitage area in the northwestern margin of the Tarim l... more ABSTRACT The nephelinite exposed in the Wajilitage area in the northwestern margin of the Tarim large igneous province (TLIP), Xinjiang, NW China display porphyritic textures with clinopyroxene, nepheline and olivine as the major phenocryst phases, together with minor apatite, sodalite and alkali feldspar. The groundmass typically has cryptocrystalline texture and is composed of crystallites of clinopyroxene, nepheline, Fe-Ti oxides, sodalite, apatite, rutile, biotite, amphibole and alkali feldspar. We report rutile SIMS U-Pb age of 268 ± 30 Ma suggesting that the nephelinite may represent the last phase of the TLIP magmatism, which is also confirmed by the field relation. The nephelinite shows depleted Sr-Nd isotopic compositions with age-corrected 87Sr/86Sr and εNd(t) values of 0.70348–0.70371 and + 3.28 to + 3.88 respectively indicating asthenospheric mantle source. Based on the reconstructed primary melt composition, the depth of magma generation is estimated as 115–140 km and the temperatures of mantle melting as 1540–1575 °C. The hotter than normal asthenospheric mantle temperature suggests the involvement of mantle thermal plume. The Mg isotope values display a limited range of δ26Mg from − 0.35 to − 0.55‰, which are lower than the mantle values (− 0.25‰). The Mg isotopic compositions, combined with the Sr-Nd isotopes and major and trace element data suggest that the Wajilitage nephelinite was most likely generated by low-degree partial melting of the hybridized carbonated peridotite/eclogite source, which we correlate with metasomatism by subducted carbonates within the early-middle Paleozoic convergent regime. A plume-lithosphere model is proposed with slight thinning of the lithosphere and variable depth and degree of melting of the carbonated mantle during the plume-lithosphere interaction. This model also accounts for the variation in lithology of the TLIP.

Research paper thumbnail of Petrogenesis of the Late Triassic Ultrapotassic Fanshan Fe-P Ore-bearing Complex in the North China Craton: Constraints on the Mineralization

Fanshan is a concentrically zoned complex with syenite in the core (unit 1), surrounded by ultram... more Fanshan is a concentrically zoned complex with syenite in the core (unit 1), surrounded by ultramafic rocks (clinopyroxenite and biotite clinopyroxene; unit 2) and the outer rim of garnet– and orthoclase clinopyroxenite (unit 3). The rocks are composed of variable amounts of diopside, biotite, orthoclase, melanite, magnetite and ap-atite, with minor primary calcite. Monomineralic apatite rocks (apatitite), nelsonite and glimerite exclusively occur in the unit 2. Geochemically, the Fanshan rocks are strongly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE; e.g., K, Rb, Ba, Sr), moderately depleted in high field strength elements (HFSE; e.g., Nb, Ta, Zr, Hf and Ti), and have a limited range of Sr–Nd–O isotopic composition (87 Sr/ 86 Sr i =0.70513– 0.70601, ε N d (t) = –6.8 to –5.5; δ 18 O= +7 –+9%. Similar mineralogy, mineral compositions, and primitive mantle– and chondrite–normalized trace element patterns observed in the three units suggest that...

Research paper thumbnail of Experimental confirmation of high temperature silicate liquid immiscibility

The existence of stable, super-liquidus silicate liquid immiscibility at temperatures up to 1200 ... more The existence of stable, super-liquidus silicate liquid immiscibility at temperatures up to 1200 °C has been proposed for some multicomponent ferrobasaltic-ferroandesitic compositions on the basis of centrifuge experiments (Veksler et al., 2007) but the evidence and interpretation of experimental results were challenged by Philpotts (2008) who argued that the products of centrifuge experiments were metastable phases formed during quenching. Here we report the results of static reverse experiments, which were aimed at resolving the debate. The idea of the reverse experiments was to test miscibility between pre-synthesized pairs of silica-rich and Fe-rich immiscible melts at static conditions and long exposure times. Three pairs of the potentially immiscible compositions were taken from the original study by Veksler et al. (2007) and one more pair was taken from a recent report of liquid immiscibility in the Panzhihua intrusion in China. Experiments were carried out in one-atmosphere ...

Research paper thumbnail of Petrogenesis of the Late Triassic Ultrapotassic Fanshan Fe-P Ore-bearing Complex in the North China Craton: Constraints on the Mineralization

Research paper thumbnail of A new clinopyroxene thermobarometer for mafic to intermediate magmatic systems

European Journal of Mineralogy

Clinopyroxene-only thermobarometry is one of the most practical tools to reconstruct crystallizat... more Clinopyroxene-only thermobarometry is one of the most practical tools to reconstruct crystallization pressures and temperatures of clinopyroxenes. Because it does not require any information of coexisting silicate melt or other co-crystallized mineral phases, it has been widely used to elucidate the physiochemical conditions of crystallizing magmas. However, previously calibrated clinopyroxene-only thermobarometers display low accuracy when being applied to mafic and intermediate magmatic systems. Hence, in this study, we present new empirical nonlinear barometric and thermometric models, which were formulated to improve the performance of clinopyroxene-only thermobarometry. Particularly, a total of 559 experimental runs conducted in the pressure range of 1 bar to 12 kbar have been used for calibration and validation of the new barometric and thermometric formulation. The superiority of our new models with respect to previous ones was confirmed by comparing their performance on 100 replications of calibration and validation, and the standard error of estimate (SEE) of the new barometer and thermometer are 1.66 kbar and 36.6 • C, respectively. Although our new barometer and thermometer fail to reproduce the entire test dataset, which has not been used for calibration and validation, they still perform well on clinopyroxenes crystallized from subalkaline basic to intermediate magmas (i.e., basaltic, basalt-andesitic, dacitic magma systems). Thus, their applicability should be limited to basaltic, basaltandesitic and dacitic magma systems. In a last step, we applied our new thermobarometer to several tholeiitic Icelandic eruptions and established magma storage conditions exhibiting a general consistency with phase equilibria experiments. Therefore, we propose that our new thermobarometer represents a powerful tool to reveal the crystallization conditions of clinopyroxene in mafic to intermediate magmas.

Research paper thumbnail of Experimental study on the effects of H2O upon crystallization in the Lower and Critical Zones of the Bushveld Complex with an emphasis on chromitite formation

Contributions to Mineralogy and Petrology

Research paper thumbnail of Geological settings and metallogenesis of high-grade iron deposits in China

Science China Earth Sciences

Research paper thumbnail of Geochemical Variation of Miocene Basalts within Shikoku Basin: Magma Source Compositions and Geodynamic Implications

Minerals

Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we r... more Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we report mineral compositions, major, trace-element, and Sr-Nd-Pb isotopic compositions of bulk-rocks from Sites C0012 (>18.9 Ma) and 1173 (13–15 Ma) of the Shikoku Basin. Samples from Sites C0012 and 1173 are tholeiitic in composition and display relative depletion in light rare earth elements (REEs) and enrichment in heavy REEs, generally similar to normal mid-ocean ridge basalts (N-MORB). Specifically, Site C0012 samples display more pronounced positive anomalies in Rb, Ba, K, Pb and Sr, and negative anomalies in Th, U, Nb, and Ta, as well as negative Nb relative to La and Th. Site 1173 basalts have relatively uniform Sr-Nd-Pb isotopic compositions, close to the end member of depleted mantle, while Site C0012 samples show slightly enriched Sr-Nd-Pb isotopic signature, indicating a possible involvement of enriched mantle 1 (EM1) and EM2 sources, which could be attributed to the metasom...

Research paper thumbnail of Mineralogical and Geochemical Study on the Yaojiazhuang Ultrapotassic Complex, North China Craton: Constraints on the Magmatic Differentiation Processes and Genesis of Apatite Ores

Frontiers in Earth Science

The differentiation process of ultrapotassic magmas is enigmatic and poorly understood. The Yaoji... more The differentiation process of ultrapotassic magmas is enigmatic and poorly understood. The Yaojiazhuang ultrapotassic complex is concentrically zoned by late-intruded syenite in the core and early emplaced clinopyroxenite in the periphery, combining a “bi-modal” lithology. Spatially, apatite and iron oxide-apatite (IOA) ores, glimmerite and pseudoleucite occur in the upper part of clinopyroxenite. The syenite and clinopyroxenite are composed of variable amounts of clinopyroxenite, biotite, K-feldspar, magnetite, apatite with minor analcite, titanite, and primary calcite. The pseudoleucite clinopyroxenite contains mainly clinopyroxene, biotite and garnet in the matrix, and nepheline–K-feldspar intergrowth with muscovite and minor celestine in the leucite pseudomorph. Geochemically, rocks of the Yaojiazhuang complex are significantly enriched in potassium (K), light rare earth elements (LREE), and large ion lithophile elements (LILE). Crustal contamination by Archean tonalite–trondhjemite–granodiorite (TTG) gneisses basement may play an important role to convert the syenitic melts from silica-undersaturation to saturation. Fractionation crystallization is supported by the mineral crystallization sequence to explain the bimodal lithologies instead of silicate liquid immiscibility. During the magmatic evolution, decompression, fractionation of volatile-poor clinopyroxene and the enhancement by CO2 may result in the exsolution of an aqueous fluid. The late-stage interactions between existing minerals and magmatic fluids in the crystal mush could be a key process in the generation of both leucite pseudomorphs and apatite/IOA ores.

Research paper thumbnail of Comparative geothermometry in high-Mg magmas from the Etendeka Province and constraints on their mantle source

Journal of Petrology

There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatur... more There is still debate whether Large Igneous Provinces (LIPs) are caused by high mantle temperatures induced by thermal plumes or by other factors that enhance melt production from the mantle. A prerequisite for assessing the thermal plume model is a reliable estimate of liquidus temperatures of the magmas produced, preferably based on more than one method of geothermometry. The study reported here compares multiple geothermometers for the Etendeka LIP, which is among the largest Phanerozoic examples and one that shows several features suggestive of a plume origin (continental flood basalt province linked via an age-progressive volcanic ridge to an active hotspot). Magnesium (Mg)-rich magmas emplaced as dikes in NW Namibia are the most primitive rocks known from this province and are thus best suited to determine the composition and melting conditions of their mantle source. Earlier studies of the Etendeka Mg-rich dikes reported high liquidus temperatures based on olivine-melt Mg-Fe ...

Research paper thumbnail of Experimental evidence for a protracted enrichment of tungsten in evolving granitic melts: implications for scheelite mineralization

Research paper thumbnail of Phase equilibria and geochemical constraints on the petrogenesis of high-Ti picrite from the Paleogene East Greenland flood basalt province

Lithos

Abstract Phase equilibrium experiments have been performed on an extremely high-Ti (5.4 wt.% TiO2... more Abstract Phase equilibrium experiments have been performed on an extremely high-Ti (5.4 wt.% TiO2) picrite from the base of the Paleogene (~55 Ma) East Greenland Flood Basalt Province. This sample has a high CaO/Al2O3 ratio (1.14), a steep rare-earth elements (REE) profile, is enriched in incompatible trace elements, and is in chemical equilibrium with highly primitive olivine. This all suggests that the picrite is a near-primary melt that did not suffer major chemical evolution during ascent from the mantle source and through the crust. Near-liquidus phase relations were determined over the pressure range of 1 atm, 1 to 1.5 GPa and at temperatures from 1094 to 1400°C. They provide an important constraint on the petrogenesis of these lavas. The high-Ti picritic melt is multi-saturated with olivine (Ol) + orthopyroxene (Opx) at 1 GPa but has only Ol or Opx on the liquidus at lower and higher pressures, respectively. This indicates the primitive melt was last equilibrated with its mantle source at relatively shallow pressure (~ 1 GPa). Melting probably started at 2-3 GPa and the picritic melt was produced by 15-30% melting of the mantle source. Such a degree of partial melting requires a mantle with a high potential temperature (1480-1530˚C). The relatively low CaO content and high FeO/MnO ratios of the most primitive East Greenland picrites, the high Ni content of olivine phenocrysts and the presence of low-Ca pyroxene (i.e., pigeonite) at high pressure in our experiments all suggest that the mantle source contained a major component of garnet pyroxenite. Residual garnet in the source could adequately explain the low Al2O3 content (7.92 wt.%) and steep REE patterns of the picrite sample. However, simple melting of a lherzolitic source, even with a major pyroxenite component, cannot explain the formation of magmas with the very high Ti contents observed in some East Greenland basalts. We therefore propose that magmas highly-enriched in Ti were produced by melting of a metasomatized mantle source containing Ti-enriched amphibole and/or phlogopite.

Research paper thumbnail of New Insights for the Formation of Kiruna-Type Iron Deposits by Immiscible Hydrous Fe-P Melt and High-Temperature Hydrothermal Processes: Evidence from El Laco Deposit

Economic Geology

The world-renowned Pliocene El Laco iron deposit in northern Chile is the youngest and the best-p... more The world-renowned Pliocene El Laco iron deposit in northern Chile is the youngest and the best-preserved Kiruna-type deposit in the world. The genesis of the El Laco Kiruna-type iron deposit—i.e., whether it is magmatic or hydrothermal in origin—is a long-standing controversy. The interstitial Fe-P phase lined by early formed magnetite crystals observed in massive ores at El Laco is morphologically and geochemically consistent with that produced by recent immiscible experiments, confirming that the massive magnetite ores were products of complete solidification of an iron-rich mush comprising early crystallized magnetite and an interstitial immiscible Fe-P melt. The hydrothermal features in geochemistry of massive magnetite are similar to the features of magnetite in altered andesites, implying a superimposed hydrothermal process. The occurrence of melt inclusions with high homogenization temperatures (>700°C) hosted by the apatite in Cristales Grandes ores indicates that the veined ores formed shortly after the massive ores genetically related to the magmatic system. Some vesicles in the massive ores and the magnetite scoriae, previously interpreted as compelling evidence of volcanic structures, are demonstrated to be the residual pore spaces formed after interstitial phases between magnetite grains were removed by postmagmatic hydrothermal fluids and the accumulated debris eroded from massive ores with minor altered andesites, respectively. Thus, we propose a two-step genetic model in which massive ores resulted from magmatic processes and then were modified by subsequent magmatic-hydrothermal alteration. This model could be applied to the metallogenesis of most Kiruna-type iron deposits.

Research paper thumbnail of Immiscible hydrous Fe-Ca-P melt and the origin of iron oxide-apatite ore deposits

Nature communications, Apr 12, 2018

The origin of iron oxide-apatite deposits is controversial. Silicate liquid immiscibility and sep... more The origin of iron oxide-apatite deposits is controversial. Silicate liquid immiscibility and separation of an iron-rich melt has been invoked, but Fe-Ca-P-rich and Si-poor melts similar in composition to the ore have never been observed in natural or synthetic magmatic systems. Here we report experiments on intermediate magmas that develop liquid immiscibility at 100 MPa, 1000-1040 °C, and oxygen fugacity conditions (fO) of ∆FMQ = 0.5-3.3 (FMQ = fayalite-magnetite-quartz equilibrium). Some of the immiscible melts are highly enriched in iron and phosphorous ± calcium, and strongly depleted in silicon (<5 wt.% SiO). These Si-poor melts are in equilibrium with a rhyolitic conjugate and are produced under oxidized conditions (~FMQ + 3.3), high water activity (aHO ≥ 0.7), and in fluorine-bearing systems (1 wt.%). Our results show that increasing aHO and fO enlarges the two-liquid field thus allowing the Fe-Ca-P melt to separate easily from host silicic magma and produce iron oxide-ap...

Research paper thumbnail of Decoupling of Mg–C and Sr–Nd–O isotopes traces the role of recycled carbon in magnesiocarbonatites from the Tarim Large Igneous Province

Geochimica et Cosmochimica Acta

Research paper thumbnail of Geochemistry and oxygen isotope composition of magnetite from the Zhangmatun deposit, North China Craton: Implications for the magmatic-hydrothermal evolution of Cornwall-type iron mineralization

Ore Geology Reviews

Abstract The Zhangmatun deposit is a high-grade skarn-type iron deposit genetically linked with a... more Abstract The Zhangmatun deposit is a high-grade skarn-type iron deposit genetically linked with a gabbroic intrusion, and it has been recognized as a typical example of “Cornwall-type” deposits in China. Electron microprobe (EMPA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data on magnetite show decreasing contents of Ti, V, Cr, Mn, Co and Ga, from the gabbro, through the skarn, and to the iron ores. Additionally, magnetite grains from the gabbro, skarn and iron ores have similar primary mantle normalized signature and chondrite-normalized REE pattern, suggesting that the Fe in them might have be derived from a common source. The δ 18 O V-SMOW values of magnetite from iron ores mainly range from 4.3‰ to 6.4‰, markedly higher than that of magmatic magnetite (3.0‰). The significantly elevated oxygen isotopes of both magnetite and the corresponding water in the hydrothermal system are considered to reflect oxygen isotopic exchange between the ore-forming fluids and 18 O-rich carbonate rocks at relatively high temperature. Thus, the magnetite in the iron ores is inferred to be predominantly precipitated from the modified ore-forming fluids, rather than directly from the unreacted primary magmatic fluids. In the time-resolved analytical signals of LA-ICP-MS, the abnormal signals of incompatible elements such as Si, Ca and Mg are attributed to the sub-microscopic silicate mineral relicts. The inference is also supported by the BSE images and chemical maps of representative magnetite. The abnormal signals of Na and K are possibly related to the micro- to nano-scale salt-bearing fluid inclusions in magnetite. Based on the geochemical characteristics of different magnetite grains and varying FeO T in the fresh and altered gabbroic rocks, we propose that the iron in the ores was mainly derived from leaching of the solidified ore-related gabbro during the contact metasomatism by hydrothermal fluids. The interaction between hydrothermal fluids and carbonate country rocks and the evolution of the ore-forming fluids, including the changes in geochemical composition, decreasing temperature and pressure, and increasing oxygen fugacity, provided the conditions for precipitation of magnetite from ore-forming fluids. Our study has potential implications in understanding the origin of ‘Cornwall-type’ deposits elsewhere world.

Research paper thumbnail of Carboniferous porphyry Cu–Au deposits in the Almalyk orefield, Uzbekistan: the Sarycheku and Kalmakyr examples

International Geology Review

ABSTRACT The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is t... more ABSTRACT The Almalyk porphyry cluster in the western part of the Central Asian Orogenic Belt is the second largest porphyry region in Asia and hence has attracted considerable attention of the geologists. In this contribution, we report the zircon U–Pb ages, major and trace element geochemistry as well as Sr–Nd isotopic data for the ore-related porphyries of the Sarycheku and Kalmakyr deposits. The zircon U–Pb ages (Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)) of ore-bearing quartz monzonite and granodiorite porphyries from the Kalmakyr deposit are 326.1 ± 3.4 and 315.2 ± 2.8 Ma, and those for the ore-bearing granodiorite porphyries and monzonite dike from the Sarycheku deposit are 337.8 ± 3.1 and 313.2 ± 2.5 Ma, respectively. Together with the previous ages, they confine multi-phase intrusions from 337 to 306 Ma for the Almalyk ore cluster. Geochemically, all samples belong to shoshonitic series and are enriched in large-ion lithophile elements relative to high field strength elements with very low Nb/U weight ratios (0.83–2.56). They show initial (87Sr/86Sr)i ratios of 0.7059–0.7068 for Kalmakyr and 0.7067–0.7072 for Sarycheku and low εNd(t) values of −1.0 to −0.1 for Kalmakyr and −2.3 to 0.2 for Sarycheku, suggesting that the magmas were dominantly derived from a metasomatized mantle wedge modified by slab-derived fluids with the contribution of the continental crust by assimilation-fractional-crystallization process. Compared to the typical porphyry Cu deposits, the ore-bearing porphyries in the Almalyk cluster are shoshonitic instead of the calc-alkaline. Moreover, although the magmatic events were genetically related to a continental arc environment, the ore-bearing porphyries at Sarycheku and Kalmakyr do not show geochemical signatures of typical adakites as reflected in some giant porphyry deposits in the Circum-Pacific Ocean, indicating that slab-melting may not have been involved in their petrogenesis.

Research paper thumbnail of Petrogenesis of the Ultrapotassic Fanshan Intrusion in the North China Craton: Implications for Lithospheric Mantle Metasomatism and the Origin of Apatite Ores

Journal of Petrology

The Fanshan intrusion in the North China Craton (NCC) is concentrically zoned with syenite in the... more The Fanshan intrusion in the North China Craton (NCC) is concentrically zoned with syenite in the core (Unit 1), surrounded by ultramafic rocks (clinopyroxenite and biotite clinopyroxenite; Unit 2), and an outer rim of garnet-rich clinopyroxenite and orthoclase clinopyroxenite and syenite (Unit 3). The intrusive rocks are composed of variable amounts of Ca-rich augite, biotite, orthoclase, melanite, garnet, magnetite and apatite, with minor primary calcite. Monomineralic apatite rocks, nelsonite and glimmerite exclusively occur in Unit 2. Geochemically, the Fanshan rocks are highly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), moderately depleted in high field strength elements (HFSE), and have a limited range of Sr-Nd-O isotopic compositions. The similar mineralogy, mineral compositions, and trace element characteristics of the three units suggest that all the rocks are co-magmatic. The parental magma is ultrapotassic and is akin to kamafugite. Very low-degree partial melting of metasomatized lithospheric mantle best explains the geochemistry and petrogenesis of the parental magmas of the Fanshan intrusion. We propose that the mantle source may have been metasomatized by a hydrous carbonate-bearing melt, which has imprinted the enriched Sr-Nd isotopic signature and incompatible element enrichment with conspicuous negative Nb-Ta-Zr-Hf-Ti anomalies and LREE enrichments. The mantle source enrichment may be correlated with oceanic sediment recycling during southward subduction of the Paleo-Asian oceanic plate during the Carboniferous and Permian. We propose that crystal settling and mechanical sorting combined with repeated primitive magma replenishment and mixing with previously fractionated magma is the predominant process responsible for the formation of the apatite ores.

Research paper thumbnail of The origin of nelsonite constrained by melting experiment and melt inclusions in apatite: The Damiao anorthosite complex, North China Craton

Gondwana Research

Models for the nelsonite formation are currently highly contentious, with liquid immiscibility an... more Models for the nelsonite formation are currently highly contentious, with liquid immiscibility and fractional crystallisation as frequently proposed formation mechanisms. The nelsonites in the Damiao massif anorthosite complex in the North China Craton are revisited here together with experimental evidence for the existence of silica-free CaO-FeO-Fe 2 O 3-TiO 2-P 2 O 5 immiscible nelsonitic liquids. Our results of differential scanning calorimetry (DSC) and internally heated pressure vessel (IHPV) demonstrate that nelsonite with the composition of one-third apatite and two-thirds Fe-Ti oxides by weight 1) completely melts well above 1450 ºC at dry condition, which is in good agreement with numerous experimental studies of the CaO-P 2 O 5-Fe x O system for metallurgical purposes; 2) does not melt at the temperature up to 1200 ºC with presence of considerable amount of volatiles, e.g., fluorine and water. Therefore, the composition of the nelsonite cannot be molten at temperatures relevant for crystallisation of the Damiao magma. A review of experimental studies of liquid immiscibility and analyses of natural immiscible glasses show that all the liquids on the Fe-and P-rich side of the miscibility gap have at least 20 wt. % of aluminosilicate components. In addition, our new analyses of apatite-hosted melt inclusions in Damiao nelsonite provide a crucial clue for the nelsonite formation. The inclusions range from ~3 to 200 µm in diameter. They are ubiquitous and meet all the morphological criteria of primary melt inclusions crystallised into assemblages of daughter minerals. Almost all assemblages contain vermiculite and/or chlorite, and some contain biotite, amphibole, phlogopite and Fe-Ti oxide. Bulk compositions of analysed inclusions show large variations in SiO 2 (20.79-50.16 wt. %) and FeO t (13.44-32.78 wt. %). With a few exceptions, the inclusions are very low in CaO (0.04-1.51 wt. %) and high in Al 2 O 3 (10-21.17 wt. %). The re-homogenized inclusions at 1200ºC obtained by IHPV show similar compositional characteristics but incorporated excessive melting of the host apatite. Nevertheless, the compositions significantly differ from those of the typical immiscible Fe-rich melts despite the high Fe content and low silica. It appears that the cumulus apatite crystallised from Fe-rich, hydrated late-stage immiscible Fe-rich melt formed by liquid immiscibility occurred in the relatively early stage, i.e. prior to the arrival of aqueous fluid phase. We propose that the inclusions at Damiao record a trend of intercumulus melt evolution, which have been through liquid-liquid immiscibility but most likely have been strongly affected by separation of a hydrothermal fluid phase and the losses of alkali and Ca silicate components from the melt into the fluid.

Research paper thumbnail of Experimental confirmation of high-temperature silicate liquid immiscibility in multicomponent ferrobasaltic systems

American Mineralogist, 2015

Research paper thumbnail of Petrogenesis of nephelinites from the Tarim Large Igneous Province, NW China: Implications for mantle source characteristics and plume–lithosphere interaction

Lithos, 2015

ABSTRACT The nephelinite exposed in the Wajilitage area in the northwestern margin of the Tarim l... more ABSTRACT The nephelinite exposed in the Wajilitage area in the northwestern margin of the Tarim large igneous province (TLIP), Xinjiang, NW China display porphyritic textures with clinopyroxene, nepheline and olivine as the major phenocryst phases, together with minor apatite, sodalite and alkali feldspar. The groundmass typically has cryptocrystalline texture and is composed of crystallites of clinopyroxene, nepheline, Fe-Ti oxides, sodalite, apatite, rutile, biotite, amphibole and alkali feldspar. We report rutile SIMS U-Pb age of 268 ± 30 Ma suggesting that the nephelinite may represent the last phase of the TLIP magmatism, which is also confirmed by the field relation. The nephelinite shows depleted Sr-Nd isotopic compositions with age-corrected 87Sr/86Sr and εNd(t) values of 0.70348–0.70371 and + 3.28 to + 3.88 respectively indicating asthenospheric mantle source. Based on the reconstructed primary melt composition, the depth of magma generation is estimated as 115–140 km and the temperatures of mantle melting as 1540–1575 °C. The hotter than normal asthenospheric mantle temperature suggests the involvement of mantle thermal plume. The Mg isotope values display a limited range of δ26Mg from − 0.35 to − 0.55‰, which are lower than the mantle values (− 0.25‰). The Mg isotopic compositions, combined with the Sr-Nd isotopes and major and trace element data suggest that the Wajilitage nephelinite was most likely generated by low-degree partial melting of the hybridized carbonated peridotite/eclogite source, which we correlate with metasomatism by subducted carbonates within the early-middle Paleozoic convergent regime. A plume-lithosphere model is proposed with slight thinning of the lithosphere and variable depth and degree of melting of the carbonated mantle during the plume-lithosphere interaction. This model also accounts for the variation in lithology of the TLIP.

Research paper thumbnail of Petrogenesis of the Late Triassic Ultrapotassic Fanshan Fe-P Ore-bearing Complex in the North China Craton: Constraints on the Mineralization

Fanshan is a concentrically zoned complex with syenite in the core (unit 1), surrounded by ultram... more Fanshan is a concentrically zoned complex with syenite in the core (unit 1), surrounded by ultramafic rocks (clinopyroxenite and biotite clinopyroxene; unit 2) and the outer rim of garnet– and orthoclase clinopyroxenite (unit 3). The rocks are composed of variable amounts of diopside, biotite, orthoclase, melanite, magnetite and ap-atite, with minor primary calcite. Monomineralic apatite rocks (apatitite), nelsonite and glimerite exclusively occur in the unit 2. Geochemically, the Fanshan rocks are strongly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE; e.g., K, Rb, Ba, Sr), moderately depleted in high field strength elements (HFSE; e.g., Nb, Ta, Zr, Hf and Ti), and have a limited range of Sr–Nd–O isotopic composition (87 Sr/ 86 Sr i =0.70513– 0.70601, ε N d (t) = –6.8 to –5.5; δ 18 O= +7 –+9%. Similar mineralogy, mineral compositions, and primitive mantle– and chondrite–normalized trace element patterns observed in the three units suggest that...

Research paper thumbnail of Experimental confirmation of high temperature silicate liquid immiscibility

The existence of stable, super-liquidus silicate liquid immiscibility at temperatures up to 1200 ... more The existence of stable, super-liquidus silicate liquid immiscibility at temperatures up to 1200 °C has been proposed for some multicomponent ferrobasaltic-ferroandesitic compositions on the basis of centrifuge experiments (Veksler et al., 2007) but the evidence and interpretation of experimental results were challenged by Philpotts (2008) who argued that the products of centrifuge experiments were metastable phases formed during quenching. Here we report the results of static reverse experiments, which were aimed at resolving the debate. The idea of the reverse experiments was to test miscibility between pre-synthesized pairs of silica-rich and Fe-rich immiscible melts at static conditions and long exposure times. Three pairs of the potentially immiscible compositions were taken from the original study by Veksler et al. (2007) and one more pair was taken from a recent report of liquid immiscibility in the Panzhihua intrusion in China. Experiments were carried out in one-atmosphere ...