Trace element compositions of apatite from the middle zone of the Panzhihua layered intrusion, SW China: Insights into the differentiation of a P- and Si-rich melt

Xing, Chang-Ming; Wang, Christina Yan; Li, Congying

doi:10.1016/j.lithos.2014.02.009

Cited by 26 publications

(17 citation statements)

References 59 publications

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“…(a) A simplified geological map showing the distribution of the Emeishan large igneous province in SW China, (b) the distribution of Fe‐Ti‐(V) oxide‐bearing mafic‐ultramafic intrusions in the Panxi region (after Shellnutt et al, ), and (c) the distribution of major rock types and Fe‐Ti oxide ores in the Panzhihua intrusion (modified after Xing et al, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

Iron Isotope Systematics of the Panzhihua Mafic Layered Intrusion Associated With Giant Fe‐Ti Oxide Deposit in the Emeishan Large Igneous Province, SW China

et al. 2019

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In order to investigate how Fe was enriched from parental high-Ti basaltic magma to form the stratigraphically thick Fe-Ti oxide ore at the bottom layers, we present a systematic study for Fe isotopic compositions of whole rocks and mineral separates (clinopyroxene, magnetite, and ilmenite) throughout the Panzhihua intrusion. Whole rock δ 56 Fe ranges from 0 ± 0.02‰ to 0.15 ± 0.04‰, consistent with the range of clinopyroxene (0.01 ± 0.02‰ to 0.16 ± 0.05‰). On the contrary, magnetite (Mt) separates have δ 56 Fe ranging from 0.17 ± 0.05‰ to 0.62 ± 0.02‰, showing a strikingly complementary trend with coexisting ilmenite (Ilm) separates (À0.52 ± 0.03‰ to À0.09 ± 0.02‰) along the profile. The calculated bulk δ 56 Fe of Fe-Ti oxides (Mt + Ilm), however, has a small range from 0.01‰ to 0.16‰, identical to those for clinopyroxene separates and whole rocks. The uniform δ 56 Fe of clinopyroxene may have resulted from the small Fe isotope fractionation between clinopyroxene and parental magma in early-stage magma differentiation before substantial crystallization of Fe-Ti oxides. The complementary trends of δ 56 Fe for Mt and Ilm along the profile and the uniform bulk δ 56 Fe of Fe-Ti oxides are better interpreted as in situ crystallization of Fe-Ti oxides from the interstitial liquid. Our Fe isotopic data and petrographic observations indicate that the thick Fe-Ti oxide ore layers in the lower zone of the Panzhihua intrusion may be attributed to in situ crystallization of Mt and Ilm from the interstitial, immiscible Fe-rich melt in the lower part of the magma chamber.Fe-Ti oxide ores and host rocks in the layered intrusions are generally composed of olivine, plagioclase, clinopyroxene, magnetite, and ilmenite in different proportions. In theory, heavy Fe isotopes are preferentially partitioned into phases with smaller coordination number (CN) or higher Fe 3+ /∑Fe than those with higher CN or lower Fe 3+ /∑Fe (Young et al., 2015). This explains why olivine, clinopyroxene, and ilmenite have similar or slightly lighter Fe isotopic compositions than the coexisting melt and why magnetite is isotopically heavier CAO ET AL.358

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Section: Geological Backgroundmentioning

confidence: 99%

Iron Isotope Systematics of the Panzhihua Mafic Layered Intrusion Associated With Giant Fe‐Ti Oxide Deposit in the Emeishan Large Igneous Province, SW China

et al. 2019

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“…In order to assess the possibility that mineral separates contain more than one mineral component, the trace element compositions of the separates were compared with two datasets: 1) LA-ICPMS from hornblende, chlorite, biotite and epidote, thin sections of Wallundry Suite samples (Iles et al, 2015), and 2) a compilation of literature values for hornblende, biotite, titanite, ilmenite, zircon and epidote in other rocks (Luhr and Carmichael, 1980;Bea et al, 1994;Bea, 1996;Bingen et al, 1996;Pan and Fleet, 1996;Ayres and Harris, 1997;Belousova et al, 2002;Hermann, 2002;Jang and Naslund, 2003;Villaseca et al, 2003;Storkey et al, 2005;Tiepolo and Tribuzio, 2005;Bea et al, 2006;Gregory et al, 2009;Acosta-Vigil et al, 2010;Driouch et al, 2010;Nehring et al, 2010;Colombini et al, 2011;Gregory et al, 2012;Starijaš Mayer et al, 2014;Xing et al, 2014). Based on these comparisons (particularly examining REE, Hf and Zr), the hornblende separates from sample J are essentially monomineralic (i.e., minimal contribution from inclusions of other phases), but the pseudomorphs after hornblende from WG are a mixture dominated by chlorite and biotite with a possible minor component similar to the titanite-epidote separate.…”

Section: Geochemistry Of Mineral Separatesmentioning

confidence: 99%

Multi-scale isotopic heterogeneity reveals a complex magmatic evolution: An example from the wallundry suite granitoids of the lachlan fold belt, Australia

Iles

Hergt²,

Woodhead³

2023

Front. Earth Sci.

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Open-system magmatic processes are expected to impart various sorts of isotopic heterogeneity upon the igneous rocks they produce. The range of processes under the “open-system” umbrella (e.g., simple two-component mixing, magma mingling, assimilation with fractional crystallization) cannot usually be uniquely identified using data from a single isotope system. The use of bulk-rock, mineral separate and in situ techniques and multiple isotope systems allows the characterization of isotopic variability at different sampling scales, illuminating details of the petrogenesis of a magmatic system. This approach has been applied to granitoids of the Wallundry Suite in the Lachlan Fold Belt, Australia. The Wallundry Suite exhibits variations in mineral assemblage, mineral composition and trends in bulk-rock major and trace element compositions consistent with the involvement of liquid-crystal sorting processes such as fractional crystallization. In situ paired O-Hf isotope data from zircon in six samples show an array indicating the isotopic evolution of the melt phase. Similarly, bulk-rock Sr-Nd-Hf isotope arrays support open-system magma evolution. These data combined with the petrographic observations and major and trace element geochemical variations suggest some form of assimilation-fractional crystallization process in the petrogenesis of the Wallundry Suite. Added complexity is revealed by two observations: 1) the isotopic variations are only weakly coupled to the lithology and major element compositions of the samples; and 2) there are distinguishable differences between the Hf isotope compositions of bulk-rock samples and those of the magmatic zircons they host. To varying degrees the rocks consistently show negative ΔεHfbulk-zrc values (i.e., the bulk-rock compositions have less radiogenic Hf isotope values than their coexisting zircons). The preservation of distinctly low Nd and Hf isotope ratios in an Fe-Ti oxide mineral separate suggests that the bulk-rock vs. zircon discrepancy is caused by the presence of unmelted components derived from a contaminant of continental origin (i.e., a rock with low Sm/Nd and Lu/Hf and thus unradiogenic Nd and Hf). Evidently, a complex interplay of assimilation, crystallization and melt segregation is required to account for the data. This investigation demonstrates that such complexity can, nevertheless, be disentangled through comparison of complementary isotope data at multiple sampling scales.

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“…The explanations for these mineral compositional reversals have been debated and may indicate that the Panzhihua intrusion opened up at least twice for the recharge of more primitive magmas (Pang et al, 2009;Song et al, 2013). Alternatively, the changes might have been induced by double-diffusion convection and multiple stratified magma layers in the magma chamber (Xing et al, 2014).…”

Section: Stratigraphic Variation In Mineral Compositionmentioning

confidence: 99%

Was the Panzhihua Large Fe‐Ti Oxide Deposit, SW China, Formed by Silicate Immiscibility?

Ding

Chen

Shao

2023

Acta Geologica Sinica (Eng)

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The Panzhihua mafic intrusion, which hosts a world‐class Fe‐Ti‐V ore deposit, is in the western Emeishan large igneous province, SW China. The formation age (∼260 Ma), Sr, and Nd isotopes indicate that the Panzhihua intrusion is part of the Emeishan large igneous province and has little crustal contamination. However, the ore genesis of the Panzhihua Fe‐Ti‐V ore deposit has been extensively debated. Two different models have been provided to explain the formation of the Panzhihua oxide deposit, namely silicate immiscibility and normal fractional crystallization. Silicate immiscibility occurrings around 1,000 °C at the late stage of basaltic magma evolution argues against the silicate immiscibility model. Apatite‐hosted melt inclusion research indicates that silicate immiscibility occurred at the late stage of Panzhihua magma evolution. However, this may have little potential to form large ore deposits like Panzhihua. However, the continuous compositional variations of the Panzhihua intrusion and the calculations by thermodynamic modelling software support the Panzhihua deposit being formed by normal fractional crystallization. The reciprocal trace element patterns of the Panzhihua intrusion and the nearby felsic rocks also coincide with the fractional crystallization model. Normal fractional crystallization of high‐Ti basaltic magma played a key role in the formation of the Panzhihua Fe‐Ti‐V ore deposit.

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Trace element compositions of apatite from the middle zone of the Panzhihua layered intrusion, SW China: Insights into the differentiation of a P- and Si-rich melt

Cited by 26 publications

References 59 publications

Iron Isotope Systematics of the Panzhihua Mafic Layered Intrusion Associated With Giant Fe‐Ti Oxide Deposit in the Emeishan Large Igneous Province, SW China

Iron Isotope Systematics of the Panzhihua Mafic Layered Intrusion Associated With Giant Fe‐Ti Oxide Deposit in the Emeishan Large Igneous Province, SW China

Multi-scale isotopic heterogeneity reveals a complex magmatic evolution: An example from the wallundry suite granitoids of the lachlan fold belt, Australia

Was the Panzhihua Large Fe‐Ti Oxide Deposit, SW China, Formed by Silicate Immiscibility?

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