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Article

Formation of Ferrogabbro Through Fe-Ti Oxide Accumulation Under Moderate Oxidation Conditions: Insights from the Dashanshu Intrusion in the Emeishan Large Igneous Province, SW China

by
Manrong Jiang
1,
Wenhao Liu
1,*,
Bo Zu
1 and
Weihua Wang
2
1
Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China
2
Sichuan Institute of Metallurgical Geology and Exploration, Chengdu 610051, China
*
Author to whom correspondence should be addressed.
Minerals 2024, 14(11), 1156; https://doi.org/10.3390/min14111156
Submission received: 25 September 2024 / Revised: 11 November 2024 / Accepted: 13 November 2024 / Published: 15 November 2024
(This article belongs to the Special Issue Petrogenesis of Large Igneous Province and Rare Earth–Rare Metal Deposits)
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Abstract

:
The mechanism of iron enrichment in ferrogabbro remains a controversial subject. This study provides valuable insights derived from the Dashanshu intrusion, located in the Emeishan Large Igneous Province in southwestern China, which features ferrogabbro with a notably high iron content (total Fe2O3 reaching up to 21.6 wt.%). The ferrogabbro samples exhibit distinctive petrographic features, including the early crystallization of plagioclase prior to pyroxenes, amphibole replacing pyroxenes, and magnetite–ilmenite intergrowth filling the interstices between plagioclase and pyroxenes. A quantitative mineral analysis based on micro-X-ray fluorescence element mapping reveals a positive correlation between Fe-Ti oxides and bulk-rock iron contents, suggesting that the formation of ferrogabbro is primarily attributed to the accumulation of Fe-Ti oxides. Petrographic characteristics combined with oxygen fugacity determinations indicate that the primitive magma had a low content of water and was moderately oxidized (ΔFMQ − 0.13 to ΔFMQ + 1.35). These conditions suppress the early crystallization of Fe-Ti oxides, thereby allowing for an enrichment of iron in the residual magma. Following the crystallization of plagioclase and pyroxenes, increased water content—evidenced by amphibole replacing pyroxenes—triggers extensive crystallization of Fe-Ti oxides. Due to their late-stage crystallization, these oxides do not settle within the magma, which possesses a high crystallinity (>50%) and consequently exhibits non-Newtonian fluid behavior. This results in the localized accumulation of Fe-Ti oxides and the formation of a ferrogabbro layer. However, the late-stage crystallization of Fe-Ti oxides also impedes the sinking and flow-sorting processes that are essential for the development of economically valuable Fe-Ti oxide layers. This may account for the lack of an economically valuable Fe-Ti oxide layer within the Dashanshu intrusion.

1. Introduction

Ferrogabbro is defined as a specific type of gabbro that is characterized by an exceptionally high iron content and a relatively low silica content. It can be distinguished from normal gabbro by its higher Fe ratio, which is defined as (Fe2O3 + FeO)/(MgO + Fe2O3 + FeO), with values exceeding 0.75 [1,2]. This category of igneous rocks is typically understood to form through a Fenner trend of primitive magma evolution, which emphasizes that low oxygen fugacity delays the crystallization time of magnetite in the magma, thereby inducing iron enrichment in the residual magma [3,4,5]. In contrast to the widely distributed iron-poor and silica-rich igneous rocks formed by the Bowen evolution trend of basaltic magma [6], iron-rich igneous rocks are rarely found at the surface but hold significant tectonic implications [7]. The Skaergaard intrusion in eastern Greenland has been regarded as a representative example of an intrusion that illustrates the Fenner evolution trend, leading to the formation of ferrogabbro [2,8]. In contrast, the widely accepted Bowen trend has also been advocated for the Skaergaard intrusion, where the formation of ferrogabbro is attributed to magnetite accumulation [9,10]. The variation in V contents from the vertical profile of the Skaergaard intrusion indicates that Fe-Ti oxides crystallized as a later interstitial phase, thereby supporting an extended Fe-enrichment trend during differentiation [5].
The Emeishan Large Igneous Province (ELIP) in southwest China is renowned for its extensive flood basalts, covering an area of at least 250,000 km2, as well as the numerous giant V-Ti magnetite ore deposits found within the layered mafic–ultramafic intrusions [11,12]. The Emeishan basalts consist of two distinct magmatic series: the high-Ti series and the low-Ti series [13,14]. The first series is associated with giant V-Ti magnetite ore deposits such as Panzhihua and Hongge, and the second series is associated with Ni-Cu–platinum group element (PGE) sulfide deposits such as Limahe [15]. Xu et al. (2003) indicated that the tholeiitic basalts spatially associated with V-Ti magnetite ore deposits evolved along a Bowen trend in an oxidized environment, which facilitated the early crystallization of magnetite. In contrast, the tholeiitic basalts located away from the V-Ti magnetite ore deposits underwent Fenner trend evolution, resulting in basalts with total Fe2O3 content reaching up to 23 wt.% [16]. Numerous studies on the genesis of V-Ti magnetite ore deposits in the ELIP have indicated that key factors influencing the enrichment of Fe−Ti oxides in magma include the following: (1) the early crystallization of silicate minerals within deep magma reservoirs, which promotes the enrichment of iron and titanium in the residual ferrogabbroic magma; (2) the crystallization of Fe-Ti oxides near the liquidus of the parent ferrogabbro magma in shallow magma chambers, along with the concentration of Fe−Ti oxides in both lower and middle zones of the chamber through flow sorting [17,18,19,20,21,22,23]. The hypotheses are supported by the presence of abundant Fe−Ti oxide inclusions found in olivine and clinopyroxene from the ore-hosting Panzhihua, Hongge, and Xinjie mafic−ultramafic layered intrusions [17,18,24]. Compared to the large layered mafic–ultramafic intrusions hosting the giant V-Ti magnetite ore deposits, the Ni-Cu-PGE deposits are hosted in small mafic–ultramafic intrusions, of which the magma evolution underwent significant crustal contamination [25,26,27]. Recent research on the magma oxygen fugacity of the ELIP indicates that high-Ti-series magmas exhibit elevated oxygen fugacity, ranging from ΔFMQ + 1.1 to ΔFMQ + 2.6. This condition facilitates the early crystallization of Fe-Ti oxides. In contrast, low-Ti-series magmas demonstrate lower oxygen fugacity values, spanning from ΔFMQ − 0.5 to ΔFMQ + 0.5, which promotes sulfide saturation [28].
In the Yanyuan region of the ELIP, the basalts and gabbroic intrusions belong to the low-Ti series [29,30]. However, these basalts and intrusions are dominated by iron mineralization, leading to iron deposits, while Ni-Cu-PGE mineralization is not developed. The iron deposits, including Pingchuan, Lanzhichang, and Niuchang, are controlled by volcanic structures and are distinguished by their low titanium content in magnetite [31] (Figure 1). Apart from these economically significant iron deposits, the Yanyuan region also hosts layered intrusions that contain disseminated Fe-Ti oxides, as exemplified by the Dashanshu intrusion [32]. The intrusion exhibits several similarities with the ferrogabbro hosting economically valuable Fe-Ti layers in the ELIP, albeit with lower iron grades falling below cut-off grade thresholds. This raises a question regarding why ferrogabbro layers were formed within low-Ti-series gabbroic intrusions while economically significant Fe-Ti oxide layers remain absent.
In this study, we conducted a comprehensive investigation of whole-rock and mineral geochemistry, along with micro-X-ray fluorescence (μXRF) element mapping, on gabbro samples from the Dashanshu intrusion. Our findings suggest that the formation of the ferrogabbro layer occurred through localized accumulation of Fe-Ti oxides in a moderately oxidized environment with increasing water content. The absence of sinking and flow-sorting processes for Fe-Ti oxides probably impeded the development of an economically viable Fe-Ti oxide layer. These findings contribute a better understanding to the genesis of ferrogabbro and associated mineralization.

2. Geological Setting

The Late–Middle Permian (~260 Ma) Emeishan Large Igneous Province consists of massive flood basalts and numerous simultaneous mafic intrusions and is located geographically in southwest China and tectonically at the western margin of the Yangtze Craton and the eastern margin of the Tibetan Plateau [11,34] (Figure 1). The basalts and related intrusions of the ELIP include two series, i.e., the high-Ti series (TiO2 > 2.5 wt.%, Ti/Y > 500) and low-Ti series (TiO2 < 2.5 wt.%, Ti/Y < 500) [13,14]. In the central part (Xichang−Panzhihua region) of the ELIP, numerous layered basic–ultrabasic rocks along with associated V-Ti magnetite and Ni-Cu-PGE sulfide deposits are distributed [11,15,22,25,35].
In the Yanyuan region west to the Xichang−Panzhihua region, the Emeishan basalt and several gabbroic intrusions are distributed along the western margin of the Jingqing fault. The basalts along the Jingqing fault include three lithologic units: the lower unit is characterized by a significant presence of basaltic breccias and agglomerates, the middle unit consists predominantly of amygdaloidal basalts, and the upper unit is primarily composed of compact basalts. From north to south, the three major gabbroic intrusions are named as Dabanshan, Dashanshu, and Maoniushan, respectively. The Dabanshan intrusion is composed of gabbro, gabbronite, and lherzolite. Picrite veins intruded into the ore-controlling faults of the Pingchuan iron deposit are situated at the western contact zone of the Dabanshan intrusion. Between the Dabanshan and Dashanshu intrusions, a submarine volcanogenic iron deposit named Lanzhichang has been identified in the lower unit of the Emeishan basalts. The Maoniushan intrusion is composed of gabbro and is associated with the Niuchang iron deposit (Figure 1).
The Dashanshu intrusion is a layered gabbroic intrusion that strikes northeast and dips northwest at angles between 45° and 80°. It is located along the northeast-trending fault and has intruded into Carboniferous limestone to the west and Ordovician sandstone to the east (Figure 2). The intrusion comprises medium- to fine-grained gabbro, with diorite intruding into the gabbro. The ferrogabbro, located centrally within the intrusion, extends 2000 m in length and varies in width from 200 to 360 m, with a dip of 45° to 70° towards the northwest. The total iron content (expressed as Fe2O3) in the ferrogabbro ranges from 15 wt.% to 23 wt.%. Due to the abundance of magnetite, which can be easily separated, the ferrogabbro is considered a low-grade iron ore body. Moving from the middle to the lower sections of the ferrogabbro, there is a noticeable increase in amphibole content, marking a gradual transition from ferrogabbro to iron-bearing amphibole gabbro.

3. Samples and Analytical Methods

Eight gabbro samples with varying magnetite contents were collected from depths of 50 to 255 m in drillcore ZK3002. All samples were prepared for thin-section analysis and subjected to whole-rock analysis for major element composition. Thin sections were examined under a polarizing microscope, and representative pairs of magnetite–ilmenite, augite–hypersthene, and amphibole minerals were selected for electron probe microanalyzer (EPMA) analysis. Sample DSS-5 was selected for zircon separation and LA-ICP-MS U-Pb dating. With the exception of sample DSS-11, micro-X-ray fluorescence (μXRF) mapping was conducted on the thin sections of the remaining seven samples.
The major element compositions of the whole-rock samples were analyzed using X-ray fluorescence spectroscopy (XRF) at ALS Chemex in Guangzhou, China, following the P61-XRF26s method. The FeO content was determined using a titrimetric method (Fe-VOL05). The Fe2O3 content was calculated by subtracting FeO from the total Fe2O3. The relative standard deviations (RSDs) for the major elements were within ±1%–2%.
Mineral compositions were analyzed with a JEOL JXA-8230 Electron Probe Microanalyzer, equipped with five wavelength-dispersive spectrometers (WDS), at the Laboratory of Microscopy and Microanalysis, Wuhan Microbeam Analysis Technology Co., Ltd. (Wuhan, China). Quantitative WDS analyses were performed under operating conditions of 15 kV accelerating voltage, a 20 nA beam current, and a 1 µm spot size. The peak counting time was 10 s for Mn, Cr, Ti, Ca, K, Na, Mg, Al, Si, Fe, and V. The background counting time was 1/2 of the peak counting time on the high- and low-energy background positions. The following standards were used: chromium oxide (Cr), rutile (Ti), microcline (K), jadeite (Na), diopside (Mg, Ca), pyrope (Al), olivine (Si), hematite (Fe), rhodonite (Mn), and vanadium (V). The peak overlap of Ti Kβ on V Kα and V Kβ on Cr Kα was corrected. Data were corrected on-line using a modified ZAF (atomic number, absorption, and fluorescence) correction procedure.
The U-Pb dating and trace element analysis of zircons were conducted simultaneously using LA-ICP-MS at the Wuhan Sample Solution Analytical Technology Company. Selected zircons were embedded in epoxy resin and polished. The samples were then photographed under transmitted and reflected light, and cathodoluminescence (CL) images were obtained using an Analytical Scanning Electron Microscope (JSM IT100) connected to a GATAN MINICL system. These images allowed for the examination of internal zircon structures and the selection of suitable spots for U-Pb analyses. Laser ablation was performed using a GeolasPro system, equipped with a COMPexPro 102 ArF excimer laser (193 nm wavelength, 200 mJ maximum energy output) and a MicroLas optical system. Ion signal intensities were measured using an Agilent 7700e ICP-MS instrument. For U-Pb dating and trace element calibration, the 91,500 zircon standard and NIST610 glass were used as reference materials. The Excel-based ICPMSDataCal 12.2 software facilitated the off-line selection and integration of background and analyzed signals, while also applying time-drift corrections and quantitative calibrations for both trace elements and U-Pb data [36]. Concordia diagrams and weighted mean calculations were generated using Isoplot/Ex_ver3.75 software [37].
A rapid and nondestructive geochemical characterization of rocks was performed using the Bruker Tornado μXRF at the China University of Geosciences, Wuhan, China. This instrument is equipped with a 30 W Rh anode metal–ceramic X-ray tube, two 30 mm2 silicon drift detectors (SDDs), and a polycapillary optic that focuses the X-ray beam to approximately 17 μm in diameter. The scanning μXRF experiments were conducted with an X-ray tube energy of 50 kV and a current of 600 μA. A step size (pixel size) of 20 μm was used, with a dwell time of 5 ms per pixel. The Advanced Mineral Identification and Characterization System (AMICS) was utilized to precisely identify mineral species and determine their area-based and weight-based percentages.

4. Results

4.1. Petrography

The Dashanshu ferrogabbro exhibits a transitional texture from gabbro to ophitic, characterized by subhedral to anhedral augite and hypersthene filling the interstices of euhedral plagioclase crystals (Figure 3A–C). Amphibole formed after the crystallization of plagioclase and pyroxenes, frequently replacing augite and hypersthene (Figure 3D). Subhedral to anhedral Fe-Ti oxides are commonly observed within the interstices of plagioclase, augite, and hypersthene, particularly in samples with higher total Fe2O3 content (Figure 3E–F). Small pyrite inclusions are found in the augite (Figure 3G). The magnetite–ilmenite intergrowths are widespread, with ilmenite occurring as lamellae or isometric crystals associated with magnetite (Figure 3H). The ilmenite lamellae within the magnetite exhibit a trellis-type texture, with large lamellae with widths ranging from 3 to 12 μm (Figure 3H) and thin lamellae measuring between 1 and 3 μm in width (Figure 3I). The coarse ilmenite is devoid of exsolution minerals. Titanite is observed at the edge of the ilmenite lamellae (Figure 3I). Accessory minerals include minor amounts of apatite, zircon, pyrrhotite, chalcopyrite, and sphalerite. In samples exhibiting alteration, chlorite commonly replaced pyroxenes.
The mineral composition revealed by μXRF element mapping provides precise insights into the mineral species and their contents in the Dashanshu gabbro (Figure 4, Table 1). Utilizing area percentage to represent volume fraction, the plagioclase content ranges from 31.82 vol.% to 45.41 vol.%, while the augite content varies between 23.13 vol.% and 36.39 vol.%. Hypersthene is found only in the least altered samples, DSS-6 and DSS-21, which exhibit minimal chlorite contents of 0.00% and 0.23%, respectively. The contents of amphibole, magnetite, and ilmenite range from 10.09 vol.% to 16.96 vol.%, 4.49 vol.% to 10.43 vol.%, and 0.92 vol.% to 3.56 vol.%, respectively. Additionally, there are several ‘unknown’ minerals, accounting for 2.13 vol.% to 5.13 vol.%, which represent those minerals that could not be identified through element mapping using the AMICS software.

4.2. Bulk-Rock Major Elements

The results of bulk-rock major element analyses for the Dashanshu gabbro are presented in Table 2. The eight samples exhibit low loss-on-ignition (LOI) values ranging from ‒0.05 wt.% to 1.46 wt.%, indicating minimal alteration effects. These samples display variable content ranges for SiO2 (42.85–50.19 wt.%), Al2O3 (12.58–16.55 wt.%), Fe2O3 (4.40–9.49 wt.%), FeO (7.06–10.85 wt.%), MgO (4.03–6.49 wt.%), and CaO (9.47–11.10 wt.%). The total iron content represented by Fe2O3 (denoted as TFe2O3) ranges from 12.24 wt.% to 21.55 wt.%. The Fe ratios of samples range from 0.72 to 0.79, with samples DSS-5 and DSS-21 lower than 0.75, while the other six samples are equal to or greater than 0.75. In the Harker diagrams, significant linear correlations between SiO2 and other oxides are observed (Figure 5). Positive linear correlations are observed for oxides of Al2O3, Na2O, K2O, and P2O5, while negative linear correlations are noted for oxides of TFe2O3, MnO, MgO, and TiO2.

4.3. Zircon U–Pb Dating

The twenty-five analyzed zircon grains exhibit a subhedral morphology, with sizes ranging from 70 to 200 μm, and display concentrated age distributions (Table 3). The Th/U ratios of the analyzed zircons vary between 0.89 and 1.79, indicating a magmatic origin. In the concordia diagrams, these grains are clustered closely around the concordia curve, yielding an intercept age of 259.78 ± 0.85 Ma (MSWD = 0.17) (Figure 6A). The calculated weighted average age based on the 206Pb/238U ratios is 259.72 ± 0.82 Ma (MSWD = 0.17) (Figure 6B). These two ages are highly consistent, and both correspond to the age of the basalts and basic intrusions associated with the ELIP (~260 Ma; [33]). Consequently, these two ages represent the formation age of the Dashanshu gabbroic intrusion.
The trace elements of zircons are presented in Table 4. The analysis of the 25 zircon grains reveals consistent chondrite-normalized rare earth element (REE) patterns (Figure 7), with total REE concentrations ranging from 671.7 ppm to 4391.7 ppm. The concentrations of Ti, Ce, and U are 3.3–12.6 ppm, 11.1–62.0 ppm, and 203–1299 ppm, respectively. Utilizing the equation established by [38], the magma oxygen fugacity was calculated based on the concentrations of Ce, U, and Ti in zircon. The results indicate a range of ΔFMQ − 0.02 to ΔFMQ + 1.83 (Table 4). In the box-and-whisker plot (Figure 8), the value of ΔFMQ + 1.83 is identified as an outlier. Consequently, the magma oxygen fugacity can be constrained to ΔFMQ − 0.02 to ΔFMQ + 1.35 based on trace element analyses of zircon.

4.4. Mineral Chemistry

4.4.1. Fe-Ti Oxides

The EPMA results for the twelve pairs of magnetite–ilmenite intergrowths are presented in Table 5. The total contents of magnetite and ilmenite yield ranges of 92.69–93.87 wt.% and 98.89–99.78 wt.%, respectively (with iron expressed as FeO). In a Ca + Al + Mn vs. Ti + V discrimination diagram [40,41], the magnetite plots within the Fe-Ti, V (porphyry) field (Figure 9), which indicates a magmatic origin. Using the methodologies proposed by [42,43], the weight percentages of Fe2O3 and FeO as well as molar percentages of ulvöspinel and ilmenite were calculated, respectively. In the FeO–Fe2O3–TiO2 diagram (Figure 10), magnetites and ilmenites plot close to the magnetite and ilmenite end members, and along the magnetite–ulvöspinel solid solution line and the ilmenite–hematite solid solution trend, respectively. This indicates that the texture involving ilmenite in magnetite resulted from the same mechanism. Utilizing the ILMAT spreadsheet developed by [44] and employing the geothermobarometer established by [45], the equilibration temperatures and oxygen fugacity were calculated. These analyses yielded equilibration temperatures ranging from 606 °C to 686 °C, along with oxygen fugacity values spanning log10 fO2 = −19.07 to −16.24, with ΔFMQ values ranging from −0.13 to +1.15 (Table 5; Figure 8; FMQ refers to the fayalite–magnetite–quartz oxygen buffer).

4.4.2. Pyroxene

The EPMA results for seven pairs of augite and hypersthene are presented in Table 6. The total contents of augite and hypersthene range from 99.93 wt.% to 100.58 wt.% and from 99.47 wt.% to 100.34 wt.%, respectively. In the Wo-En-Fs ternary diagram for Ca-Mg-Fe pyroxenes, the augites identified under a polarizing microscope fall within the fields designated for both augite and diopside, whereas hypersthenes are plotted in the clinoenstatite or enstatite field (Figure 11). The Mg# values for augite range from 0.66 to 0.71, while those for hypersthene range from 0.75 to 0.78. The iron index refers to the molar ratio of TFe/(TFe + MgO) and ranges from 0.22 to 0.25 for augite and from 0.29 to 0.34 for hypersthene. Utilizing the two-pyroxene thermometers and barometers established by [46], we calculated crystallization temperatures ranging from 844.6 to 957.5 °C, along with pressures between 3.2 and 4.9 kbar for these pyroxenes. The Fe-Mg exchange coefficients for the analyzed pairs of augite and hypersthene vary between 0.62 and 0.80, aligning with an equilibrium value of approximately 0.7 ± 0.2 typical for subsolidus systems [46]; this indicates that equilibrium is achieved between the two pyroxenes.

4.4.3. Amphibole

The EPMA results for eleven amphibole grains are presented in Table 7. The total contents of amphiboles range from 96.05 wt.% to 97.63 wt.%. The Mg# values range from 0.58 to 0.65. Using the Amp-TB spreadsheet proposed by [48], the amphibole species was identified as magnesiohornblende. Additionally, the temperature, pressure, and melt-water content were calculated. The amphibole crystallization temperature is 758–60 °C, the pressure is 66–171 MPa, and the water content in the melt is 3.4–5.6 wt.% (Table 7).

5. Discussion

5.1. Formation Mechanism of Dashanshu Ferrogabbro

Research on the basalts and gabbro from the Dabanshan intrusion in the Yanyuan area indicate that (1) the basalts and gabbro belong to the low-Ti-series igneous rocks of ELIP; (2) the primitive magma of these rocks was originated from the spinel lherzolite of the lithosphere mantle; and (3) magma evolution was dominated by the crystallization fractionation of olivine and pyroxenes, with minimal crustal contamination [29,30,31]. For the Dashanshu intrusion, the TiO2 content of the gabbro samples ranges from 1.44 wt.% to 2.62 wt.%, but in most samples it does not exceed 2.50 wt.% (Table 2). Considering the accumulation process of Fe-Ti oxides during the formation of the Dashanshu intrusion, as discussed below, it can be inferred that the titanium content in the magma is likely to be lower. Thus, the gabbro associated with the Dashanshu intrusion can be classified as the low-Ti-series igneous rocks of the ELIP. However, the Dashanshu gabbro samples exhibit elevated total iron contents (TFe2O3 ranging from 12.24 wt.% to 21.55 wt.%) and Fe ratios (0.72–0.76) compared to the gabbro of the Dabanshan intrusion. Six samples of the Dashanshu intrusion demonstrate an Fe ratio equal to or exceeding 0.75, which serves as a boundary for distinguishing ferrogabbro from normal gabbro in the Skaergaard intrusion in eastern Greenland [2] (Figure 12). Consequently, these gabbro samples of the Dashanshu intrusion could be classified as ferrogabbro.
The Harker diagrams of the gabbro samples from Dashanshu intrusion show significant linear correlations between SiO2 and other oxides (Figure 5). Generally, these linear correlations could be explained as the crystallization fractionation process from ultrabasic to basic. Specifically, the linear correlations of SiO2 and Fe2O3 (Figure 5C) and SiO2 and TiO2 (Figure 5F) indicate the crystallization fraction of magnetite and ilmenite, respectively. However, the Fe-Ti oxides were crystallized later than plagioclase and pyroxenes, as evidenced by the petrographic observations of abundant subhedral to anhedral Fe-Ti oxides within the interstices of plagioclase, augite, and hypersthene (Figure 3E–G). As will be discussed in Section 5.2, by the time the Fe-Ti oxides crystallized, the magma containing abundant plagioclases and pyroxenes behaved as a non-Newtonian fluid, preventing the Fe-Ti oxides from settling. Thus, the crystallization fractionation of the Fe-Ti oxides did not occur after the crystallization of plagioclase and pyroxenes in the magma of the Dashanshu intrusion.
After excluding the possible Fe-Ti oxide crystallization fraction process, the linear correlations of SiO2 and Fe2O3 (Figure 5C) and SiO2 and TiO2 (Figure 5F) possibly indicate a cumulus process, which generates the same linear correlations between SiO2 and other oxides as those seen in the crystallization fraction process. The accurate mineral species and volume and weight percentage revealed by the μXRF results enable us to quantitatively assess the relationship between the mineral contents of Fe-Ti oxides and the chemical iron contents in the Dashanshu gabbro. As shown in Figure 10, the bulk-rock total Fe2O3 contents show no correlation with the contents of pyroxenes and amphibole but are positively correlated with the combined contents of magnetite and ilmenite (Figure 13A–C). Specifically, the bulk-rock Fe2O3 contents correlate positively with magnetite contents (Figure 13D). In addition, the compositions of magnetite indicate that the magnetite in the Dashanshu gabbro is a magmatic origin instead of hydrothermal origin (Figure 9). These findings strongly indicate that the accumulation of Fe-Ti oxides, particularly magnetite, is responsible for the unusually high chemical iron content in the Dashanshu gabbro. In summary, the Dashanshu ferrogabbro was formed primarily through the accumulation of Fe-Ti oxides, especially magnetite. This observation is analogous to the petrographic characteristics of the ferrogabbro found in the Skaergaard intrusion located in eastern Greenland, which exhibits magnetite cumulate within its ferrogabbro layers [2].

5.2. Magma Conditions Controlling Enrichment of Fe-Ti Oxides

In the evolution of basaltic magma, water content and oxygen fugacity are two critical factors that determine crystallization sequences and trends in magma evolution. In anhydrous basaltic magma, plagioclase crystallizes before clinopyroxene, while in hydrous basaltic magma, clinopyroxene forms prior to plagioclase [49,50,51]. The presence of orthopyroxene, a nominally anhydrous mineral [52], indicates an anhydrous environment. In contrast, amphibole, a hydrous mineral, signifies nearly water-saturated conditions within the basaltic magma [53,54]. Both water content and oxygen fugacity play significant roles in magnetite crystallization. In hydrous and oxidized basaltic magma, magnetite tends to crystallize close to or on the liquidus line, whereas in anhydrous and reduced environments, magnetite crystallization is inhibited [53,54,55,56,57,58]. The crystallization behavior of ilmenite appears to be largely independent of the melt oxidation state but primarily depends on the TiO2 content within the melt [54,56].
Detailed petrographic investigations, complemented by electron probe microanalysis, have elucidated several key findings regarding the magma conditions and evolution of the Dashanshu intrusion: (1) plagioclase crystallized prior to augite (Figure 3A–C); (2) the presence of hypersthene is noted (Figure 3A–D,F; Table 1), alongside equilibrium between augite and hypersthene (Table 6); (3) amphibole replaces pyroxenes (Figure 3D), while Fe-Ti oxides occupy the interstices between plagioclase and pyroxenes (Figure 3E–G); (4) there are pyrite rather than magnetite inclusions in the augite (Figure 3G); (5) there are widespread magnetite–ilmenite intergrowths (Figure 3H–I); and (6) the melt-water content ranged from approximately 3.4 to 5.6 wt.% when amphibole was present (Table 7). The overall crystallization sequence of the rock-forming minerals is as follows: plagioclase → augite + hypersthene → amphibole + titanomagnetite (magnetite + ilmenite) → biotite. The widespread intergrowths of magnetite and ilmenite are indicative of the subsolidus exsolutions derived from primary titanomagnetite related to slow cooling [59]. The pyroxenes were crystallized at temperatures ranging from 844.6 °C to 957.5 °C (Table 6). Subsequently, the amphibole and primary titanomagnetite formed nearly contemporaneously at temperatures between 758 °C and 860 °C (Table 7). These findings, in conjunction with established theories of magma evolution, provide significant insights into the conditions and evolutionary trends associated with the Dashanshu intrusion. Notably, during the initial stages of mineral crystallization, the magma likely contained low levels of water and exhibited moderate to low oxygen fugacity. However, a significant increase in water content occurred following the crystallization of pyroxenes.
Our analyses of zircon and magnetite–ilmenite aggregates allow for precise constraints on the oxygen fugacity of the magma. The oxygen fugacity derived from zircon trace elements ranges from ΔFMQ − 0.02 to ΔFMQ + 1.83, with an average of ΔFMQ + 0.60. The values obtained from magnetite–ilmenite compositions vary from ΔFMQ − 0.13 to ΔFMQ + 1.15, averaging ΔFMQ + 0.39. Collectively, these results indicate that the oxidation state of the magma is moderate; notably, there was a slight decrease in oxygen fugacity during the crystallization of Fe-Ti oxides (Figure 8). This observation aligns with the understanding that the crystallization of magnetite consumes ferric iron [55]. The moderate oxidation state, combined with the low-content water conditions present during the early stages of magma evolution, likely inhibited the early crystallization of Fe-Ti oxides [54,56].
In summary, the evolutionary path of the magma can be outlined based on specific conditions. In an environment characterized by low water content and a moderate oxidation state, plagioclase crystallizes first, followed by clinopyroxene and hypersthene. This crystallization sequence enhances the enrichment of iron in the residual magma. When the volume percentage of plagioclase and pyroxene crystals in the magma exceeds 50 vol.%, the melt-water content increases to between 3.4 and 5.6 wt.%, resulting in the crystallization of amphibole and a substantial quantity of Fe-Ti oxides. The accumulation of these Fe-Ti oxides within a confined layer contributes to the formation of ferrogabbro in the Dashanshu gabbroic intrusion. The magma exhibiting high crystallinity (>50%) demonstrates non-Newtonian fluid behavior, which inhibits the sinking of late-crystallized Fe-Ti oxides within the magma [60,61,62]. This process resulted in a localized accumulation of Fe-Ti oxides in the gabbro and the formation of a ferrogabbro layer. However, the processes of sinking and flow sorting for Fe-Ti oxides were absent, which may explain the lack of an economically valuable Fe-Ti oxide layer within the Dashanshu intrusion.

6. Conclusions

  • The crystallization sequence of rock-forming minerals in the Dashanshu gabbro is as follows: plagioclase → augite + hypersthene → amphibole + titanomagnetite (comprising magnetite and ilmenite) → biotite. The formation of ferrogabbro is attributed to the localized accumulation of substantial amounts of titanomagnetite, which exsolved into magnetite and ilmenite during a slow cooling process.
  • The low water content and moderately oxidized nature of the primitive magma inhibit the early crystallization of Fe-Ti oxides, facilitating iron enrichment in the residual magma. An increased water content following the crystallization of plagioclase and pyroxenes promotes the formation of amphibole along with a significant abundance of Fe-Ti oxides.
  • As Fe-Ti oxides crystallize, magma with a crystallinity exceeding 50% exhibits non-Newtonian fluid behavior. This characteristic inhibits the sinking of late-crystallized Fe-Ti oxides within the magma, thereby facilitating the formation of a ferrogabbro layer. However, this process also leads to the absence of economically valuable Fe-Ti oxide layers.

Author Contributions

Conceptualization, W.L.; methodology, M.J. and B.Z.; software, B.Z.; validation, M.J.; formal analysis, M.J.; investigation, M.J. and W.W.; resources, W.L.; data curation, M.J. and W.L.; writing—original draft preparation, W.L.; writing—review and editing, M.J., B.Z. and W.W.; visualization, M.J.; supervision, W.L.; project administration, M.J. and W.L.; funding acquisition, W.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by the National Natural Science Foundation of China (Grant Nos. 41902083 and 41602077).

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Regional geological map of the central Emeishan Large Igneous Province. Modified from [33].
Figure 1. Regional geological map of the central Emeishan Large Igneous Province. Modified from [33].
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Figure 2. Sketch map of Dashanshu gabbroic intrusion.
Figure 2. Sketch map of Dashanshu gabbroic intrusion.
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Figure 3. Petrographic images of Dashanshu gabbroic intrusion: (A–C) gabbroophitic texture and mineral composition of the Dashanshu intrusion; (D) amphiboles replacing augite and hypersthene; (E,F) abundant subhedral to anhedral Fe-Ti oxides distributed in the interstice of plagioclase, augite, and hypersthene; (G) pyrite inclusions in augite; (H) ilmenite occurring as lamellae and grained phase; (I) trellis-type texture of fine-grained ilmenite. Abbreviations: Pl, plagioclase; Aug, augite; Hy, hypersthene; Bt, biotite; FeTiO, Fe-Ti oxides; Am, amphibole; Chl, chlorite; Mt, magnetite; Ilm, ilmenite; Py, pyrite; Po, pyrrhotite; Ttn, titanite; Hm, hematite. Images (A,C,D,F) were taken under plane-polarized light. Image (B) was taken under cross-polarized light. Images (E,G,H) were taken under reflected light. Image (I) was taken under a scanning electron microscope.
Figure 3. Petrographic images of Dashanshu gabbroic intrusion: (A–C) gabbroophitic texture and mineral composition of the Dashanshu intrusion; (D) amphiboles replacing augite and hypersthene; (E,F) abundant subhedral to anhedral Fe-Ti oxides distributed in the interstice of plagioclase, augite, and hypersthene; (G) pyrite inclusions in augite; (H) ilmenite occurring as lamellae and grained phase; (I) trellis-type texture of fine-grained ilmenite. Abbreviations: Pl, plagioclase; Aug, augite; Hy, hypersthene; Bt, biotite; FeTiO, Fe-Ti oxides; Am, amphibole; Chl, chlorite; Mt, magnetite; Ilm, ilmenite; Py, pyrite; Po, pyrrhotite; Ttn, titanite; Hm, hematite. Images (A,C,D,F) were taken under plane-polarized light. Image (B) was taken under cross-polarized light. Images (E,G,H) were taken under reflected light. Image (I) was taken under a scanning electron microscope.
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Figure 4. Mineral composition of Dashanshu gabbro as revealed by micro-X-ray fluorescence (μXRF) element mapping: (A–G) display all the minerals present in the gabbro, while (H–N) illustrate the enhanced distributions of magnetite and ilmenite.
Figure 4. Mineral composition of Dashanshu gabbro as revealed by micro-X-ray fluorescence (μXRF) element mapping: (A–G) display all the minerals present in the gabbro, while (H–N) illustrate the enhanced distributions of magnetite and ilmenite.
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Figure 5. Harker diagrams for the Dashanshu gabbro (A–I).
Figure 5. Harker diagrams for the Dashanshu gabbro (A–I).
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Figure 6. (A) Zircon U–Pb concordia diagrams with represented zircon CL image and (B) weighted average 206Pb/238U age plots of the Dashanshu gabbro. The dashed circle in the zircon CL image denotes the position of the U–Pb age and trace element analysis.
Figure 6. (A) Zircon U–Pb concordia diagrams with represented zircon CL image and (B) weighted average 206Pb/238U age plots of the Dashanshu gabbro. The dashed circle in the zircon CL image denotes the position of the U–Pb age and trace element analysis.
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Figure 7. Chondrite-normalized REE patterns of zircon. Normalization values are from [39].
Figure 7. Chondrite-normalized REE patterns of zircon. Normalization values are from [39].
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Figure 8. Box and whisker plot for oxygen fugacity determined by compositions of zircon and magnetite–ilmenite solid solution.
Figure 8. Box and whisker plot for oxygen fugacity determined by compositions of zircon and magnetite–ilmenite solid solution.
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Figure 9. Ca + Al + Mn versus Ti + V discrimination diagram (after [40,41]) for the magnetite in the Dashanshu gabbro. BIF, banded iron formation; IOCG, iron oxide copper–gold.
Figure 9. Ca + Al + Mn versus Ti + V discrimination diagram (after [40,41]) for the magnetite in the Dashanshu gabbro. BIF, banded iron formation; IOCG, iron oxide copper–gold.
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Figure 10. Compositional ranges of the magnetite–ulvöspinel solid solutions and ilmenite–hematite solid solution of magnetite containing ilmenite lamellae within the FeO(+ MnO + MgO)–Fe2O3(+ Al2O3 + Cr2O3)–TiO2 diagram.
Figure 10. Compositional ranges of the magnetite–ulvöspinel solid solutions and ilmenite–hematite solid solution of magnetite containing ilmenite lamellae within the FeO(+ MnO + MgO)–Fe2O3(+ Al2O3 + Cr2O3)–TiO2 diagram.
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Figure 11. Plot of Ca-Mg-Fe pyroxenes in the Wo-En-Fs ternary diagram (after [47]) for the Dashanshu gabbro.
Figure 11. Plot of Ca-Mg-Fe pyroxenes in the Wo-En-Fs ternary diagram (after [47]) for the Dashanshu gabbro.
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Figure 12. Diagram of total Fe2O3 content versus (Fe2O3 + FeO)/(Fe2O3 + FeO + MgO) ratio to distinguish ferrogabbro from normal gabbro. Data of Dabanshan intrusion are from [30], and data from Skaergaard intrusion are from [2].
Figure 12. Diagram of total Fe2O3 content versus (Fe2O3 + FeO)/(Fe2O3 + FeO + MgO) ratio to distinguish ferrogabbro from normal gabbro. Data of Dabanshan intrusion are from [30], and data from Skaergaard intrusion are from [2].
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Figure 13. Content correlations between (A) augite + hypersthene and total Fe2O3, (B) amphibole and total Fe2O3, (C) magnetite + ilmenite and total Fe2O3, and (D) magnetite and Fe2O3 of the Dashanshu gabbro.
Figure 13. Content correlations between (A) augite + hypersthene and total Fe2O3, (B) amphibole and total Fe2O3, (C) magnetite + ilmenite and total Fe2O3, and (D) magnetite and Fe2O3 of the Dashanshu gabbro.
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Table 1. Mineral contents revealed by micro-X-ray fluorescence (μXRF) element mapping.
Table 1. Mineral contents revealed by micro-X-ray fluorescence (μXRF) element mapping.
Sample No.MineralAugiteHypersthenePlagioclaseAmphiboleBiotiteChloriteCalciteApatiteMagnetiteIlmeniteTitanitePyritePyrrhotiteChalcopyriteSphaleriteUnknownTotal
Density3.43.42.683.073.093.22.713.195.154.723.485.014.64.24.0
DSS-5Area (μm2)154,278,042/302,843,736 106,978,086 38,411,927 2,358,475 133,935 544,708 29,949,998 6,143,664 2,374,674 1,423,532 /54,673 /21,275,162 666,770,613
Area (%)23.13/45.41 16.04 5.77 0.35 0.02 0.08 4.49 0.92 0.34 0.20 /0.01 /3.19 99.95
Weight (%)25.79/39.91 16.14 5.83 0.37 0.02 0.09 7.58 1.42 0.40 0.35 /0.01 /2.09 100.00
DSS-6Area (μm2)105,739,68715,442,286 147,468,066 45,802,918 200,863 11,697 93,575 290,808 36,505,118 12,908,099 53,644 5,133,715 /93,172 /9,312,320 379,055,968
Area (%)27.90 4.07 38.92 12.08 0.05 0.00 0.02 0.08 9.63 3.38 0.01 1.35 /0.03 /2.46 99.98
Weight (%)28.92 4.22 31.78 11.30 0.05 0.00 0.02 0.08 15.12 4.91 0.02 2.06 /0.03 /1.50 100.01
DSS-13Area (μm2)158,257,095 /138,437,53766,232,3837,423,94613,547,415 /483,919 27,136,193 10,359,856 132,478 3,558,091 //130,453 9,275,739 434,975,104
Area (%)36.39 /31.82 15.22 1.70 3.11 /0.11 6.24 2.39 0.03 0.81 //0.03 2.13 99.98
Weight (%)38.27 /26.37 14.46 1.63 3.08 /0.11 9.93 3.49 0.03 1.27 //0.03 1.32 99.99
DSS-14Area (μm2)149,710,000 /192,853,200 99,442,400 11,391,600 19,770,400 953,600 636,000 61,131,200 20,935,200 154,800 6,979,600 69,600 /40,000 22,452,400 586,520,000
Area (%)25.53 /32.86 16.96 1.97 3.37 0.16 0.11 10.43 3.56 0.03 1.19 0.01 /0.01 3.83 100.02
Weight (%)26.40 /26.81 15.83 1.83 3.29 0.14 0.11 16.33 5.13 0.03 1.81 0.02 /0.01 2.33 100.07
DSS-18Area (μm2)115,752,091 /157,165,624 50,513,937 3,241,592 13,877,336 14,108 52,804 28,455,633 11,582,585 309,568 1,642,563 ///17,406,730 400,014,570
Area (%)28.92 /39.29 12.63 0.82 3.47 0.00 0.01 7.12 2.90 0.08 0.41 ///4.35 100.00
Weight (%)31.01 /33.20 12.20 0.80 3.49 0.00 0.01 11.54 4.29 0.08 0.65 ///2.74 100.01
DSS-19Area (μm2)163,085,034 /228,852,866 71,859,546 35,511,562 42,278,263 //37,778,880 9,052,045 5,595,788 2,329,008 345,706 //32,328,904 629,017,602
Area (%)25.91 /36.39 11.42 5.66 6.72 //5.99 1.43 0.89 0.36 0.06 //5.14 99.97
Weight (%)28.17 /31.18 11.21 5.59 6.88 //9.88 2.17 0.99 0.60 0.08 //3.29 100.04
DSS-21Area (μm2)98,306,400 37,185,600 160,275,200 40,951,200 478,000 913,600 /328,000 33,749,600 13,897,600 256,000 3,377,600 ///15,794,000 405,512,800
Area (%)24.25 9.17 39.50 10.09 0.11 0.23 /0.08 8.33 3.42 0.06 0.84 ///3.89 99.97
Weight (%)25.50 9.65 32.81 9.60 0.11 0.23 /0.08 13.27 5.01 0.07 1.29 ///2.41 100.03
Table 2. Major element contents (wt.%) of the Dashanshu gabbro.
Table 2. Major element contents (wt.%) of the Dashanshu gabbro.
Sample No.DSS-5DSS-6DSS-11DSS-13DSS-14DSS-18DSS-19DSS-21
SiO250.1942.8546.0347.0145.1645.3949.0144.35
TiO21.442.552.252.072.622.621.632.14
Al2O316.0812.7914.6012.8113.0812.5816.5513.46
Fe2O34.409.496.856.828.478.324.867.69
FeO7.06 10.85 9.509.25 10.5510.607.2110.80
MnO0.160.200.170.170.180.170.160.20
MgO4.496.494.645.485.145.394.036.44
CaO11.1011.009.4710.559.789.7510.2510.45
Na2O3.192.173.333.042.962.913.792.17
K2O0.700.250.570.480.450.510.810.37
P2O50.090.040.110.080.070.070.030.05
Cr2O30.030.010.010.010.030.020.010.01
LOI 0.790.371.460.880.280.511.1−0.05
Total99.7299.0698.9998.6598.7798.8499.4498.08
TFe2O312.2421.5517.4117.1020.1920.1012.8719.69
Fe ratio0.720.760.780.750.790.780.750.74
TFe2O3 = Fe2O3 + FeO/0.9; TFe2O3 was not included in the total contents. Fe ratio = (Fe2O3 + FeO)/(Fe2O3 + FeO + MgO).
Table 3. Results of in situ U–Pb LA–ICP–MS zircon analyses of the Dashanshu gabbro.
Table 3. Results of in situ U–Pb LA–ICP–MS zircon analyses of the Dashanshu gabbro.
SpotTh
(ppm)		U
(ppm)		Th/U207Pb/206Pb207Pb/235U206Pb/238U207Pb/206Pb207Pb/235U206Pb/238Udisc.4f206
Ratio1σRatio1σRatio1σAge (Ma)1σAge (Ma)1σAge (Ma)1σ
DSS-5-01585 417 1.40 0.0506 0.0017 0.2859 0.0094 0.0410 0.0004 220 75.9 255 7.4 259 2.4 2.00%−0.0011
DSS-5-02388 304 1.28 0.0544 0.0017 0.3100 0.0097 0.0413 0.0004 387 68.5 274 7.5 261 2.3 5.00%0.0037
DSS-5-03557 528 1.06 0.0502 0.0013 0.2833 0.0068 0.0410 0.0003 211 59.2 253 5.4 259 2.0 3.00%−0.0016
DSS-5-04884 561 1.58 0.0492 0.0014 0.2794 0.0076 0.0411 0.0003 167 60.2 250 6.0 259 1.9 4.00%−0.0028
DSS-5-05509 387 1.31 0.0508 0.0017 0.2911 0.0096 0.0414 0.0003 235 77.8 259 7.6 261 2.0 1.00%−0.0007
DSS-5-06943 604 1.56 0.0498 0.0014 0.2830 0.0079 0.0410 0.0003 183 66.7 253 6.2 259 2.2 3.00%−0.0021
DSS-5-07329 252 1.31 0.0516 0.0019 0.2913 0.0105 0.0410 0.0004 333 80.5 260 8.3 259 2.7 1.00%0.0002
DSS-5-081303 750 1.74 0.0515 0.0012 0.2930 0.0069 0.0410 0.0003 265 55.6 261 5.4 259 1.8 1.00%0.0001
DSS-5-09537 429 1.25 0.0518 0.0015 0.2961 0.0087 0.0413 0.0003 276 68.5 263 6.8 261 1.9 1.00%0.0004
DSS-5-101028 735 1.40 0.0532 0.0013 0.3031 0.0071 0.0411 0.0003 339 53.7 269 5.5 260 1.7 4.00%0.0023
DSS-5-111193 895 1.33 0.0516 0.0012 0.2939 0.0068 0.0411 0.0003 265 55.6 262 5.3 260 1.7 1.00%0.0002
DSS-5-121653 986 1.68 0.0515 0.0012 0.2948 0.0070 0.0413 0.0003 265 55.6 262 5.5 261 1.8 1.00%0.0001
DSS-5-13235 264 0.89 0.0543 0.0022 0.3063 0.0124 0.0409 0.0004 383 92.6 271 9.6 258 2.4 5.00%0.0036
DSS-5-14432 409 1.06 0.0538 0.0016 0.3050 0.0092 0.0409 0.0003 365 68.5 270 7.2 258 1.9 5.00%0.0031
DSS-5-151499 837 1.79 0.0513 0.0014 0.2908 0.0073 0.0410 0.0003 257 61.1 259 5.7 259 2.0 1.00%−0.0001
DSS-5-16387 308 1.26 0.0527 0.0018 0.2990 0.0102 0.0411 0.0004 317 79.6 266 8.0 260 2.3 3.00%0.0016
DSS-5-17345 298 1.16 0.0541 0.0025 0.3076 0.0148 0.0411 0.0004 372 105.5 272 11.5 259 2.4 5.00%0.0033
DSS-5-18438 334 1.31 0.0551 0.0023 0.3101 0.0120 0.0409 0.0004 417 90.7 274 9.3 259 2.7 6.00%0.0047
DSS-5-19872 705 1.24 0.0504 0.0014 0.2861 0.0077 0.0411 0.0003 213 63.0 256 6.1 259 1.8 2.00%−0.0013
DSS-5-20281 302 0.93 0.0491 0.0017 0.2791 0.0097 0.0412 0.0003 150 83.3 250 7.7 260 2.1 4.00%−0.0030
DSS-5-21444 412 1.08 0.0522 0.0016 0.2970 0.0089 0.0412 0.0003 295 70.4 264 7.0 260 1.9 2.00%0.0010
DSS-5-22234 203 1.15 0.0541 0.0022 0.3060 0.0121 0.0410 0.0004 376 92.6 271 9.4 259 2.5 5.00%0.0034
DSS-5-231021 739 1.38 0.0532 0.0024 0.3020 0.0129 0.0411 0.0004 339 100.0 268 10.1 260 2.6 4.00%0.0022
DSS-5-242305 1299 1.77 0.0515 0.0014 0.2942 0.0081 0.0412 0.0003 261 64.8 262 6.3 261 2.0 1.00%0.0000
DSS-5-25298 259 1.15 0.0504 0.0018 0.2867 0.0098 0.0413 0.0004 213 83.3 256 7.7 261 2.5 2.00%−0.0013
disc. = discordance. 4f206 = (common 206Pb)/(total measured 206Pb) based on measured 204Pb.
Table 4. Trace element of in situ LA–ICP–MS zircon analyses of the Dashanshu gabbro and calculated oxygen fugacity.
Table 4. Trace element of in situ LA–ICP–MS zircon analyses of the Dashanshu gabbro and calculated oxygen fugacity.
SpotPTiYNbLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaPbThU△FMQ
DSS-5-01492 7.35 2789 1.94 0.031 21.6 0.27 4.97 10.5 3.38 65.3 22.0 250 93.3 408 79.6 708 138 9579 0.96 24.7 585 417 0.60
DSS-5-02381 7.95 2055 1.20 0.017 14.1 0.24 3.62 7.13 2.39 45.3 15.1 179 68.3 302 60.5 538 105 9396 0.62 17.71 388 304 0.07
DSS-5-03533 12.6 2420 4.67 0.0042 38.2 0.083 1.77 4.18 1.24 31.3 12.8 180 75.5 367 76.1 698 138 9535 1.71 28.6 557 528 0.92
DSS-5-04587 8.39 3985 3.09 0.037 38.3 0.40 8.83 18.4 5.49 100 33.2 372 136 584 113 976 184 9573 1.26 34.3 884 561 1.23
DSS-5-05431 9.42 2515 1.37 0.032 17.8 0.30 3.85 8.59 2.56 56.8 18.6 218 82.8 370 74.4 671 132 8742 0.76 22.5 509 387 0.12
DSS-5-06493 8.95 3015 1.85 0.063 25.1 0.28 5.13 9.71 3.51 64.9 22.1 263 101 453 92.0 831 164 8674 1.04 36.4 943 604 0.37
DSS-5-07394 10.8 1847 1.12 0.17 14.2 0.27 4.24 6.73 2.09 42.6 14.2 164 61.7 271 54.2 481 94.6 8985 0.64 14.41 329 252 -0.02
DSS-5-08588 9.33 3756 3.16 0.070 36.3 0.33 5.78 13.2 4.95 86.1 28.7 338 125 557 113 1005 194 9372 1.35 46.8 1303 750 0.79
DSS-5-09473 6.67 2545 0.85 0.019 19.1 0.22 4.24 7.92 2.20 53.7 18.7 221 83.9 372 73.6 655 127 9662 0.48 24.2 537 429 0.45
DSS-5-10552 7.85 3473 3.48 0.046 29.0 0.29 4.06 8.06 2.35 57.0 21.3 283 115 525 109 982 194 10,024 1.45 43.0 1028 735 0.56
DSS-5-11558 7.67 3335 0.61 0.037 31.6 0.37 5.43 11.5 3.11 74.9 24.5 293 110 500 99.0 881 170 9274 0.38 51.5 1193 895 0.57
DSS-5-12689 6.27 4705 4.25 0.098 62.0 0.47 8.80 18.1 5.08 107 35.5 416 158 705 141 1249 243 9847 1.78 61.4 1653 986 1.83
DSS-5-13447 9.83 1292 2.36 0.0031 18.5 0.046 1.33 2.12 0.70 18.9 6.84 94.2 40.2 197 41.9 396 81.9 9480 1.04 13.77 235 264 0.48
DSS-5-14516 3.97 901 1.07 0.0010 15.3 0.051 0.61 1.75 0.66 13.4 5.02 65.8 28.3 141 30.8 304 65.5 9678 0.79 22.1 432 409 0.56
DSS-5-15540 7.12 3808 3.28 0.061 39.5 0.40 5.62 15.0 5.49 87.8 29.2 342 129 556 111 982 190 8338 1.44 53.2 1499 837 1.07
DSS-5-16449 6.17 2455 1.64 0.015 17.8 0.21 4.18 8.05 2.10 53.8 18.4 214 80.8 352 69.2 610 117 10,163 0.98 17.52 387 308 0.68
DSS-5-17423 5.27 1856 0.80 0.040 15.0 0.18 3.17 5.95 1.71 37.6 13.1 157 60.3 272 55.0 482 93.9 10,532 0.62 16.78 345 298 0.56
DSS-5-18387 8.47 2125 1.07 0.052 14.6 0.28 3.38 7.47 2.40 45.5 14.9 177 70.5 316 65.4 596 119 8352 0.68 19.3 438 334 0.00
DSS-5-19427 4.90 3181 1.00 0.051 26.5 0.33 4.95 10.7 2.68 70.0 23.7 279 105 460 90.6 805 156 9163 0.55 39.8 872 705 0.86
DSS-5-20386 11.4 1509 2.66 0.0056 21.7 0.080 1.26 3.48 1.00 21.1 8.34 112 47.1 227 48.6 448 93.2 9630 1.05 15.92 281 302 0.51
DSS-5-21313 4.55 1229 0.95 0.0054 16.8 0.086 1.12 2.66 0.77 20.3 7.32 93.0 39.4 190 42.2 402 85.8 9988 0.85 22.4 444 412 0.60
DSS-5-22338 6.80 1556 0.68 0.0089 11.1 0.13 2.50 5.40 1.61 35.1 11.5 133 51.5 227 46.4 408 81.2 9113 0.51 11.37 234 203 0.14
DSS-5-23482 3.33 3357 1.24 0.018 29.7 0.33 5.07 8.90 2.36 67.3 24.1 290 112 495 99.8 878 171 10,432 0.71 43.1 1021 739 1.35
DSS-5-24747 7.49 6785 3.69 0.054 38.5 0.42 6.75 14.4 5.14 125 46.9 583 228 1004 205 1790 346 8465 1.09 83.6 2305 1299 0.61
DSS-5-25314 7.03 1670 0.99 0.016 12.7 0.23 3.05 5.34 1.31 29.4 10.7 136 54.2 246 51.0 457 92.3 10,199 0.54 14.38 298 259 0.13
Table 5. Composition of Fe–Ti oxides from the Dashanshu gabbro and calculated temperature and oxygen fugacity.
Table 5. Composition of Fe–Ti oxides from the Dashanshu gabbro and calculated temperature and oxygen fugacity.
SpotDSS-6-Mt-1 DSS-6-Ilm-1 DSS-6-Mt-2 DSS-6-Ilm-2 DSS-6-Mt-3 DSS-6-Ilm-3 DSS-6-Mt-4 DSS-6-Ilm-4 DSS-6-Mt-5 DSS-6-Ilm-5 DSS-6-Mt-6 DSS-6-Ilm-6 DSS-18-Mt-1 DSS-18-Ilm-1 DSS-18-Mt-2 DSS-18-Ilm-2 DSS-18-Mt-3 DSS-18-Ilm-3 DSS-18-Mt-4 DSS-18-Ilm-4 DSS-18-Mt-5 DSS-18-Ilm-5 DSS-18-Mt-6 DSS-18-Ilm-6
SiO20.84 0.03 0.03 0.02 0.05 0.02 0.13 0.02 0.01 0.03 0.05 0.04 0.07 0.02 0.07 0.03 0.06 0.03 0.08 0.00 0.07 0.03 0.49 0.00
TiO2 3.41 49.01 2.88 49.80 2.92 50.14 3.32 48.44 3.86 49.67 2.62 48.72 3.64 49.82 2.78 49.80 1.77 48.84 1.92 49.58 2.06 49.81 1.62 49.59
Al2O3 1.29 0.03 1.41 0.03 2.11 0.07 2.06 0.05 1.29 0.05 1.28 0.06 1.66 0.01 1.80 0.05 1.13 0.04 1.52 0.02 0.67 0.00 0.43 0.02
TFeO85.49 47.52 87.94 47.71 86.53 46.90 85.60 47.72 86.83 47.80 88.26 48.49 87.02 47.81 88.01 47.58 89.52 48.80 88.26 47.84 89.98 47.78 89.40 47.69
MnO0.21 1.27 0.17 1.49 0.11 1.20 0.23 1.20 0.17 1.15 0.19 1.63 0.22 1.67 0.14 1.72 0.09 1.61 0.03 1.45 0.13 1.79 0.07 1.75
MgO 0.26 0.95 0.13 0.33 0.39 1.24 0.56 1.21 0.26 0.76 0.04 0.12 0.06 0.08 0.07 0.09 0.04 0.12 0.04 0.10 0.00 0.03 0.12 0.03
CaO 0.03 0.02 0.01 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.01 0.00 0.01 0.00 0.00 0.04 0.01 0.02 0.01 0.02 0.00
Na2O 0.02 0.02 0.02 0.00 0.02 0.01 0.01 0.00 0.01 0.03 0.02 0.03 0.01 0.02 0.00 0.01 0.01 0.00 0.01 0.02 0.00 0.00 0.01 0.00
K2O 0.00 0.00 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.00
Cr2O30.02 0.00 0.05 0.03 0.01 0.05 0.02 0.03 0.06 0.00 0.03 0.02 0.01 0.02 0.06 0.02 0.02 0.01 0.03 0.05 0.02 0.00 0.02 0.05
V2O3 1.10 0.16 1.17 0.17 1.24 0.16 1.15 0.22 1.23 0.17 1.13 0.16 0.96 0.11 0.87 0.14 0.91 0.12 0.89 0.08 0.91 0.09 0.79 0.06
Total92.6999.0193.8499.7893.499.7793.198.8993.7599.6593.6699.2693.6799.5893.8299.4593.5799.5992.8399.1593.8799.5392.9999.19
Fe2O3 56.75 99.01 60.40 99.78 59.17 99.77 58.18 98.89 58.51 99.65 60.94 99.26 58.52 99.58 60.30 99.45 63.07 99.59 61.68 99.15 63.22 99.53 62.91 99.19
FeO34.42 7.11 33.59 5.82 33.29 5.77 33.25 8.32 34.18 6.24 33.43 7.21 34.36 5.36 33.75 5.19 32.77 7.43 32.75 5.46 33.09 5.35 32.79 5.45
Si0.033 0.001 0.001 0.000 0.002 0.000 0.005 0.001 0.000 0.001 0.002 0.001 0.003 0.000 0.003 0.001 0.002 0.001 0.003 0.000 0.003 0.001 0.019 0.000
Ti0.099 0.930 0.083 0.942 0.084 0.942 0.095 0.917 0.111 0.938 0.075 0.928 0.104 0.947 0.080 0.947 0.051 0.927 0.055 0.946 0.059 0.948 0.047 0.947
Al0.059 0.001 0.063 0.001 0.095 0.002 0.093 0.001 0.058 0.001 0.058 0.002 0.075 0.000 0.081 0.001 0.051 0.001 0.069 0.001 0.030 0.000 0.020 0.000
Fe3+1.644 0.135 1.731 0.110 1.695 0.108 1.671 0.158 1.680 0.118 1.752 0.137 1.681 0.102 1.726 0.099 1.814 0.141 1.785 0.104 1.817 0.102 1.823 0.104
Fe2+1.108 0.867 1.070 0.893 1.060 0.871 1.061 0.847 1.090 0.885 1.068 0.889 1.097 0.908 1.074 0.908 1.048 0.889 1.054 0.911 1.057 0.909 1.056 0.908
Mn0.007 0.027 0.006 0.032 0.004 0.025 0.007 0.026 0.006 0.025 0.006 0.035 0.007 0.036 0.004 0.037 0.003 0.034 0.001 0.031 0.004 0.038 0.002 0.038
Mg0.015 0.036 0.008 0.012 0.022 0.046 0.032 0.045 0.015 0.028 0.002 0.004 0.003 0.003 0.004 0.004 0.002 0.004 0.002 0.004 0.000 0.001 0.007 0.001
Ca0.001 0.000 0.000 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.001 0.000 0.001 0.000
Na0.001 0.001 0.001 0.000 0.001 0.000 0.001 0.000 0.001 0.001 0.002 0.001 0.001 0.001 0.000 0.000 0.001 0.000 0.001 0.001 0.000 0.000 0.001 0.000
K0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000
Cr0.001 0.000 0.001 0.001 0.000 0.001 0.001 0.000 0.002 0.000 0.001 0.000 0.000 0.000 0.002 0.000 0.001 0.000 0.001 0.001 0.001 0.000 0.001 0.001
V0.034 0.003 0.036 0.003 0.038 0.003 0.035 0.004 0.038 0.003 0.035 0.003 0.029 0.002 0.027 0.003 0.028 0.002 0.028 0.002 0.028 0.002 0.025 0.001
Total cations3.001 2.001 3.001 2.000 3.001 2.000 3.001 2.000 3.001 2.001 3.001 2.001 3.001 2.001 3.000 2.000 3.000 2.000 3.000 2.000 3.000 2.000 3.000 2.000
No. of oxygen species4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000 4.000 3.000
Mol % Ulvöspinel10.35% 8.56% 8.78% 9.99% 11.49% 7.80% 10.86% 8.28% 5.24% 5.74% 6.05% 4.81%
Mol % Ilmenite 93.03% 94.52% 94.40% 91.86% 93.91% 92.83% 94.70% 94.84% 92.65% 94.63% 94.68% 94.58%
Temperature (oC)671 635 639 686 661 659 643 627 641 614 615 606
log10fO2−17.02 −18.53 −18.39 −16.24 −17.67 −17.10 −18.53 −18.91 −17.29 −18.98 −18.99 −19.07
△FMQ0.58 0.09 0.13 0.95 0.19 0.82 −0.13 −0.05 1.15 0.28 0.23 0.43
Table 6. Composition of pyroxene from the Dashanshu gabbro and calculated temperature and pressure.
Table 6. Composition of pyroxene from the Dashanshu gabbro and calculated temperature and pressure.
Sample No.DSS-6-CpxD-01 DSS-6-OpxD-01 DSS-6-CpxD-02 DSS-6-OpxD-02 DSS-6-CpxD-03 DSS-6-OpxD-03 DSS-6-CpxD-04 DSS-6-OpxD-04 DSS-6-CpxD-05 DSS-6-OpxD-05 DSS-6-CpxD-06 DSS-6-OpxD-06 DSS-6-CpxD-07 DSS-6-OpxD-07
SiO2 52.75 53.27 52.18 53.18 53.19 53.84 53.96 53.81 52.76 52.69 53.29 53.80 52.83 53.87
TiO2 0.42 0.34 0.55 0.35 0.23 0.33 0.10 0.27 0.38 0.30 0.27 0.23 0.26 0.24
Al2O3 1.37 1.18 1.52 1.03 0.88 0.93 0.49 0.77 1.22 0.88 0.94 0.68 1.33 0.69
Cr2O30.02 0.00 0.00 0.00 0.02 0.00 0.00 0.01 0.02 0.00 0.03 0.01 0.00 0.00
V2O3 0.03 0.03 0.07 0.02 0.04 0.01 0.02 0.04 0.03 0.01 0.04 0.05 0.08 0.02
FeO 8.83 18.58 9.16 18.37 8.63 18.05 7.53 19.52 8.79 20.60 8.85 18.80 8.34 18.95
MnO0.29 0.50 0.27 0.51 0.37 0.50 0.33 0.63 0.29 0.65 0.35 0.60 0.33 0.57
MgO 15.10 24.27 15.12 24.24 14.78 24.68 14.94 23.88 15.15 22.85 14.90 24.30 14.85 24.45
CaO20.97 1.73 20.72 1.73 21.98 1.63 22.79 1.37 21.01 1.60 21.61 1.28 21.78 1.34
Na2O0.35 0.03 0.33 0.04 0.29 0.05 0.18 0.04 0.34 0.05 0.32 0.03 0.34 0.03
K2O0.00 0.01 0.00 0.01 0.00 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00
Total100.13 99.93 99.93 99.47 100.42 100.02 100.33 100.34 100.00 99.62 100.58 99.75 100.14 100.15
Si1.953 1.955 1.938 1.960 1.968 1.969 1.994 1.976 1.956 1.959 1.968 1.980 1.956 1.974
Ti0.012 0.009 0.015 0.010 0.006 0.009 0.003 0.008 0.011 0.008 0.007 0.006 0.007 0.007
IVAl0.047 0.045 0.062 0.040 0.032 0.031 0.006 0.024 0.044 0.039 0.032 0.020 0.044 0.026
VIAl0.013 0.006 0.004 0.005 0.006 0.009 0.015 0.009 0.010 0.001 0.009 0.009 0.014 0.004
Cr0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.001 0.000 0.001 0.000 0.000 0.000
V0.001 0.001 0.002 0.001 0.001 0.000 0.001 0.001 0.001 0.000 0.001 0.001 0.002 0.001
Fe3+0.029 0.019 0.041 0.016 0.027 0.006 0.000 0.001 0.030 0.022 0.025 0.000 0.031 0.009
Fe2+0.245 0.552 0.244 0.551 0.240 0.546 0.235 0.598 0.242 0.616 0.248 0.580 0.227 0.572
Mn0.009 0.015 0.009 0.016 0.012 0.015 0.010 0.020 0.009 0.020 0.011 0.019 0.010 0.018
Mg0.834 1.328 0.837 1.332 0.815 1.346 0.823 1.307 0.838 1.266 0.820 1.333 0.819 1.336
Ca0.832 0.068 0.824 0.069 0.871 0.064 0.902 0.054 0.835 0.064 0.855 0.051 0.864 0.053
Na0.025 0.002 0.024 0.003 0.021 0.004 0.013 0.003 0.025 0.003 0.023 0.002 0.024 0.002
K0.000 0.001 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Total cations4.000 4.000 4.000 4.000 4.000 4.000 4.002 4.000 4.000 3.998 4.000 4.001 4.000 4.000
No. of oxygen species6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000 6.000
Mg/(Mg + TFe)0.75 0.70 0.75 0.70 0.75 0.71 0.78 0.69 0.75 0.66 0.75 0.70 0.76 0.70
TFe/(Mg + TFe)0.25 0.30 0.25 0.30 0.25 0.29 0.22 0.31 0.25 0.34 0.25 0.30 0.24 0.30
Wo43.67 3.50 43.45 3.52 45.36 3.27 46.02 2.74 43.74 3.28 44.58 2.57 45.36 2.68
En43.77 68.31 44.12 68.38 42.44 68.86 41.97 66.74 43.89 65.25 42.75 67.89 43.02 68.19
Fs12.56 28.19 12.42 28.10 12.20 27.87 12.01 30.51 12.37 31.47 12.67 29.54 11.62 29.13
KD(Fe-Mg)0.76 0.80 0.80 0.62 0.64 0.77 0.72
Temperature (oC)946.3 957.5 912.0 844.6 928.3 911.2 901.2
Pressure (kbar)3.9 3.2 3.4 3.8 4.9 4.9 4.5
Table 7. Composition of amphibole from the Dashanshu gabbro and calculated temperature, pressure, and water content.
Table 7. Composition of amphibole from the Dashanshu gabbro and calculated temperature, pressure, and water content.
SpotDSS-6-01 DSS-6-02 DSS-6-03 DSS-6-04 DSS-6-05 DSS-6-06 DSS-18-01 DSS-18-02 DSS-18-03 DSS-18-04 DSS-18-05
SiO247.36 48.19 46.54 47.63 47.17 46.74 44.95 47.70 44.65 48.84 45.75
TiO2 1.38 1.31 1.46 1.28 1.30 1.28 1.87 1.18 1.58 1.32 2.01
Al2O3 6.18 5.50 6.86 5.79 6.15 6.41 8.15 5.33 8.66 5.00 7.81
Cr2O3 0.03 0.00 0.01 0.04 0.00 0.01 0.00 0.09 0.01 0.00 0.00
V2O3 0.09 0.07 0.08 0.11 0.04 0.07 0.03 0.10 0.09 0.01 0.11
FeO 13.55 12.99 12.91 13.54 13.51 13.43 13.57 16.45 15.46 13.14 12.44
MnO 0.23 0.18 0.18 0.15 0.25 0.19 0.15 0.23 0.18 0.27 0.19
MgO 14.07 15.04 14.38 14.53 14.13 14.06 13.63 12.86 12.11 14.88 14.83
CaO 11.74 11.35 11.48 11.48 11.58 11.61 11.47 11.26 11.63 10.89 11.27
Na2O 1.12 1.12 1.31 1.09 1.11 1.17 2.23 1.27 1.95 1.38 2.25
K2O 0.56 0.40 0.51 0.45 0.50 0.59 0.50 0.47 0.51 0.50 0.43
Cl 0.35 0.22 0.32 0.28 0.36 0.36 0.22 0.23 0.14 0.20 0.08
F 0.04 0.17 0.00 0.04 0.18 0.12 0.21 0.12 0.11 0.10 0.45
Total 96.69 96.56 96.05 96.40 96.28 96.06 96.95 97.27 97.08 96.53 97.63
Si6.980 7.031 6.866 6.992 6.971 6.934 6.659 7.041 6.657 7.124 6.671
Ti0.152 0.144 0.162 0.141 0.144 0.143 0.208 0.131 0.177 0.144 0.221
Al1.074 0.946 1.193 1.001 1.071 1.121 1.422 0.928 1.522 0.859 1.342
Cr0.004 0.000 0.001 0.005 0.000 0.001 0.000 0.011 0.001 0.000 0.000
Fe3+0.525 0.763 0.650 0.726 0.621 0.584 0.470 0.706 0.435 0.716 0.637
Fe2+1.145 0.822 0.943 0.937 1.049 1.083 1.212 1.325 1.493 0.887 0.880
Mn0.029 0.022 0.022 0.018 0.032 0.024 0.019 0.028 0.023 0.033 0.024
Mg3.091 3.272 3.163 3.180 3.112 3.110 3.010 2.831 2.692 3.236 3.224
Ca1.853 1.775 1.815 1.805 1.833 1.845 1.820 1.780 1.857 1.702 1.760
Na0.320 0.316 0.375 0.309 0.317 0.337 0.639 0.362 0.563 0.390 0.636
K0.105 0.075 0.096 0.085 0.094 0.112 0.094 0.089 0.097 0.094 0.080
Total cations15.279 15.166 15.286 15.198 15.245 15.294 15.554 15.232 15.516 15.186 15.476
No. of oxygen23.000 23.000 23.000 23.000 23.000 23.000 23.000 23.000 23.000 23.000 23.000
speciesMg-HblMg-HblMg-HblMg-HblMg-HblMg-HblMg-HblMg-HblMg-HblMg-HblMg-Hbl
Mg/(Ma + TFe)0.65 0.67 0.67 0.66 0.65 0.65 0.64 0.58 0.58 0.67 0.68
Temperature (°C)792 780 813 782 790 800 860 765 855 758 855
Uncertainty 22 22 22 22 22 22 22 22 22 22 22
Pressure (MPa)90 75 107 81 90 96 149 73 172 66 132
Uncertainty (max error)10 8 12 9 10 11 16 8 19 7 15
H2Omelt (wt.%)4.3 4.1 4.5 4.2 4.4 4.3 4.4 4.3 5.6 3.4 3.8
Uncertainty0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4
Mg-Hbl: magnesiohornblende.
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MDPI and ACS Style

Jiang, M.; Liu, W.; Zu, B.; Wang, W. Formation of Ferrogabbro Through Fe-Ti Oxide Accumulation Under Moderate Oxidation Conditions: Insights from the Dashanshu Intrusion in the Emeishan Large Igneous Province, SW China. Minerals 2024, 14, 1156. https://doi.org/10.3390/min14111156

AMA Style

Jiang M, Liu W, Zu B, Wang W. Formation of Ferrogabbro Through Fe-Ti Oxide Accumulation Under Moderate Oxidation Conditions: Insights from the Dashanshu Intrusion in the Emeishan Large Igneous Province, SW China. Minerals. 2024; 14(11):1156. https://doi.org/10.3390/min14111156

Chicago/Turabian Style

Jiang, Manrong, Wenhao Liu, Bo Zu, and Weihua Wang. 2024. "Formation of Ferrogabbro Through Fe-Ti Oxide Accumulation Under Moderate Oxidation Conditions: Insights from the Dashanshu Intrusion in the Emeishan Large Igneous Province, SW China" Minerals 14, no. 11: 1156. https://doi.org/10.3390/min14111156

APA Style

Jiang, M., Liu, W., Zu, B., & Wang, W. (2024). Formation of Ferrogabbro Through Fe-Ti Oxide Accumulation Under Moderate Oxidation Conditions: Insights from the Dashanshu Intrusion in the Emeishan Large Igneous Province, SW China. Minerals, 14(11), 1156. https://doi.org/10.3390/min14111156

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