Base metal mineral segregation and Fe-Mg exchange inducing extreme compositions of olivine and chromite from the Xiadong Alaskan-type complex in the southern part of the Central Asian Orogenic Belt

Bai, Yang; Su, Ben‐Xun; Chen, Chen; Yang, Sai-Hong; Liang, Zi; Xiao, Yan; Qin, Kezhang; Malaviarachchi, Sanjeewa P.K.

doi:10.1016/j.oregeorev.2017.01.023

Cited by 20 publications

(19 citation statements)

References 56 publications

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“…In olivine, two elements, such as Al and Sc, or Li and P, are normally coupled to substitute for Mg and/or Si or to occupy vacancies to maintain charge balance [79][80][81]. Meanwhile, trivalent cations in olivine generally diffuse more slowly than divalent ones [33,37] Partition coefficients of V, Cr, Mn and Zn in olivine are highly variable from compatible to incompatible and appear to be susceptible to subsolidus reequilibration that is controlled not only by the temperature, but also by the distribution of the dominant divalent cations in coexisting chromite [17,33,34,73,82,83].…”

Section: Partition Coefficients Of Trace Elements In Chromite and Olimentioning

confidence: 99%

Distinctive melt activity and chromite mineralization in Luobusa and Purang ophiolites, southern Tibet: constraints from trace element compositions of chromite and olivine

Zhou

Jing

et al. 2019

Science Bulletin

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Section: Partition Coefficients Of Trace Elements In Chromite and Olimentioning

confidence: 99%

Distinctive melt activity and chromite mineralization in Luobusa and Purang ophiolites, southern Tibet: constraints from trace element compositions of chromite and olivine

Zhou

Jing

et al. 2019

Science Bulletin

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“…Elemental exchange with coexisting silicate minerals is another important factor modifying the composition of spinel [61][62][63][64][65], and is commonly induced by the variation of physical conditions [66][67][68][69]. Generally, diffusion-induced zonation is caused by the long-term exchange between crystals subjected to continuous, high subsolidus temperatures [23,[70][71][72].…”

Section: Elemental Exchange With Coexisting Silicate Mineralsmentioning

confidence: 99%

Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton

Bai

Xiao

et al. 2018

Minerals

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Abstract:We conducted petrological and mineral chemistry investigations of Cr-spinel in ultramafic rocks of the Yanmenguan mafic-ultramafic complex in the North China Craton. The Cr-spinel grains occur as inclusions in enstatite, tschermakite, phlogopite, and olivine, or as interstitial grains among the aforementioned silicate minerals, and show concentric or asymmetrical textures. Back-scattered electron and elemental images and compositional profiles of the spinel grains indicate the presence of Cr-and Fe-rich cores and Al-and Mg-rich rims. The host silicate minerals display a decrease in Al and Mg contents accompanied by an increase in Cr and Fe away from the spinel. These textures and compositional variations suggest that subsolidus elemental exchange more likely gave rise to the compositional zonation, resulting in the transfer of Al and Mg from the silicate minerals to the spinel. The Mn, Ni, and Ti contents in spinel and the major elements of olivine-hosted spinel are relatively stable during subsolidus elemental diffusion and thus are more reliable tracers of primary high-temperature processes. The temperature estimates reveal that the subsolidus diffusion might have occurred at 600-720 • C, which could be linked to the regional metamorphic event.

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“…The exsolved ilmenite lamellae in olivine were mostly reported in UHP peridotite (Hacker Gray circle in Fig. 8a represents the olivine from Alaskan-type complexes worldwide (Bai et al, 2017). The field of mantle olivine in the Fig.…”

Section: Exsolved Lamellae In Olivine Grain From Previous Studiesmentioning

confidence: 98%

Exsolution Lamellae in Olivine Grains of Dunite Units from Different Types of Mafic‐Ultramafic Complexes

Liang

Xiao

Thakurta

et al. 2018

Acta Geologica Sinica (Eng)

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Exsolution microstructures in olivine grains from dunite units in a few selected tectonic environments are reported here. They include lamellae of clinopyroxene and clinopyroxene‐magnetite intergrowth in the Gaositai and Yellow Hill Alaskan‐type complexes, clinopyroxene‐magnetite intergrowth in the Kızıldağ ophiolite, and chromite lamellae in the Hongshishan mafic‐ultramafic intrusive complex. These lamellae commonly occur as needle‐ or rod‐like features and are oriented in olivine grains. The host olivine grains have Fo contents of 92.5–92.6 in the Gaositai complex, 86.5–90.1 in the Yellow Hill complex, 93.2–93.4 in the Kızıldağ ophiolite and 86.9–88.3 in the Hongshishan complex. Clinopyroxene in the rod‐like intergrowth exsolved in olivine grains in the Gaositai and Yellow Hill is diopside with similar major element compositions of CaO (23.6–24.3wt%), SiO2 (52.2–54.0wt%), Al2O3 (0.67–2.15wt%), Cr2O3 (0.10–0.42wt%) and Na2O (0.14–0.26wt%). It falls into the compositional field of hydrothermal clinopyroxene and its origin is thus probably related to reaction between dunite and fluids. The enrichment of the fluids in Ca2+, Fe3+, Cr3+ and Na+, resulted in elevated concentrations of these cations in olivine solid solutions via the reaction. With decreasing temperature, the olivine solid solutions altered to an intergrowth of magnetite and clinopyroxene. The Fe3+ and Cr3+ preferentially partitioned into magnetite, while Ca2+ and Na+ entered clinopyroxene. Since the studied Alaskan‐type complexes and ophiolite formed in a subduction environment, the fluids were probably released from the subducted slab. In contrast, the exsolved chromite in olivine grains from the Hongshishan complex that formed in post‐orogenic extension setting can be related to olivine equilibrated with Cr‐bearing liquid. Similarly, these lamellae have all been observed in serpentine surrounding olivine grains, indicating genetic relations with serpentinization.

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Base metal mineral segregation and Fe-Mg exchange inducing extreme compositions of olivine and chromite from the Xiadong Alaskan-type complex in the southern part of the Central Asian Orogenic Belt

Cited by 20 publications

References 56 publications

Distinctive melt activity and chromite mineralization in Luobusa and Purang ophiolites, southern Tibet: constraints from trace element compositions of chromite and olivine

Distinctive melt activity and chromite mineralization in Luobusa and Purang ophiolites, southern Tibet: constraints from trace element compositions of chromite and olivine

Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton

Exsolution Lamellae in Olivine Grains of Dunite Units from Different Types of Mafic‐Ultramafic Complexes

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