Origin of ultrahigh pressure and highly reduced minerals in podiform chromitites and associated mantle peridotites of the Luobusa ophiolite, Tibet

Xu, Xing; Yang, Jingsui; Robinson, Paul T.; Xiong, Fahui; Ba, Dengzhu; Guo, Guolin

doi:10.1016/j.gr.2014.05.010

Cited by 89 publications

(54 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since then, the idea that podiform chromitites are formed through reaction between mantle peridotites (especially harzburgites) and boninitic or tholeiitic melts has attracted considerable attention from many scholars (Arai and Yurimoto, 1994;Zhou et al, 1994Zhou et al, , 1996Zhou et al, , 1997Arai, 1997;Edwards et al, 2000;Rollinson and Adetunji, 2013;Arai et al, 2015). However, occurrence of ultrahigh pressure (UHP) and highly reduced minerals (e.g., diamond and moissanite) strongly suggests that podiform chromitites are formed at mantle depths of 150-300 km or even greater (Yang et al, 1981;Bai et al, 2001Bai et al, , 2002Bai et al, , 2004Bai et al, , 2007Yang et al, 2002Yang et al, , 2007Yang et al, , 2013Yang et al, , 2014Yang et al, , 2015aXu et al, 2008Xu et al, , 2009Xu et al, , 2013Xu et al, , 2015.…”

Section: Introductionmentioning

confidence: 99%

Mineralogy and Geochemistry of the High‐Cr Podiform Chromitite from the Cuobuzha Ophiolite, Yarlung Zangbo Suture Zone, Western Tibet, China: Implication for its Origin

Zhao

Yang

Liu

et al. 2020

Acta Geologica Sinica (Eng)

Self Cite

View full text Add to dashboard Cite

The Cuobuzha high‐Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements (PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios (<0.1). In mid‐ocean ridge basalts (MORB)‐normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic boninites in the Bonin and Thetford Mines. Approximately 20 platinum group mineral (PGM) grains were discovered from the samples, including laurite, erlichmanite, Os‐Fe alloy, cuproiridsite, and irarsite. The PGM assemblages indicate that sulfur fugacity was initially low enough to allow the precipitation of Os‐Fe alloy and increased thereafter, with the fall in temperature. Primary Fe‐Ni and Fe‐Cr alloys, which are stable in a highly reduced environment, occur as inclusions within chromites or clinopyroxenes. Calculated results show that the parental magma has an intimate affinity with boninites. Based on our observations, a model is proposed wherein the Cuobuzha chromitites contain high‐pressure and low‐pressure chromites. Low‐pressure chromites were formed via reaction between boninitic melts and peridotites, during which the high‐pressure chromites hosting highly reduced minerals were mobilized by melts and were reallocated to podiform chromitites.

show abstract

Section: Introductionmentioning

confidence: 99%

Mineralogy and Geochemistry of the High‐Cr Podiform Chromitite from the Cuobuzha Ophiolite, Yarlung Zangbo Suture Zone, Western Tibet, China: Implication for its Origin

Zhao

Yang

Liu

et al. 2020

Acta Geologica Sinica (Eng)

Self Cite

View full text Add to dashboard Cite

show abstract

“…These studies include: major and trace elemental and/or isotopic compositions of different textural chromitites and their host peridotites (e.g., [1][2][3][4][5][6][7][8]), and unusual ultrahigh-pressure (UHP), highly reduced and crustally derived minerals found either in situ or as separates in the chromitites and peridotites (e.g., [9][10][11][12][13][14][15][16][17][18][19][20][21]). [42]), and the distribution of magmatism on the Lhasa terrane (modified from Chung et al [43]).…”

Section: Introductionmentioning

confidence: 99%

“…The Luobusa ophiolite originated at a mid-ocean ridge spreading center at 177 ± 31 Ma and was later modified by supra-subduction zone (SSZ) magmatism at 120 ± 10 Ma involving an intra-oceanic subduction system [5][6][7]41,53,54]. However, the presence of ultrahigh-pressure (UHP) and highly reduced minerals such as diamond, coesite, and native elements, initially found in the chromitites but more recently also in their host peridotites, requires additional processes or models to outline the genesis of the chromitites (e.g., [4,10,11,13,[17][18][19][20][55][56][57]). …”

Section: Introductionmentioning

confidence: 99%

Timing of Secondary Hydrothermal Alteration of the Luobusa Chromitites Constrained by Ar/Ar Dating of Chrome Chlorites

Guo

et al. 2018

Minerals

View full text Add to dashboard Cite

Chrome chlorites are usually found as secondary phases formed by hydrothermal alteration of chromite deposits and associated mafic/ultramafic rocks. Here, we report the 40 Ar/ 39 Ar age of chrome chlorites separated from the Luobusa massive chromitites which have undergone secondary alteration by CO 2 -rich hydrothermal fluids. The dating results reveal that the intermediate heating steps (from 4 to 10) of sample L7 generate an age plateau of 29.88 ± 0.42 Ma (MSWD = 0.12, plateau 39 Ar = 74.6%), and the plateau data points define a concordant inverse isochron age of 30.15 ± 1.05 Ma (MSWD = 0.08, initial 40 Ar/ 36 Ar = 295.8 ± 9.7). The Ar release pattern shows no evidence of later degassing or inherited radiogenic component indicated by an atmospheric intercept, thus representing the age of the hydrothermal activity. Based on the agreement of this hydrothermal age with the~30 Ma adakitic plutons exposed in nearby regions (the Zedong area, tens of kilometers west Luobusa) and the extensive late Oligocene plutonism distributed along the southeastern Gangdese magmatic belt, it is suggested that the hydrothermal fluids are likely related to the~30 Ma magmatism. The hydrothermal fluid circulation could be launched either by remote plutons (such as the Sangri granodiorite, the nearest~30 Ma pluton west Luobusa) or by a similar coeval pluton in the local Luobusa area (inferred, not found or reported so far). Our results provide important clues for when the listwanites in Luobusa were formed.

show abstract

“…The identification of ultra-high pressure (UHP) phases in chromitites and harzburgites of ophiolite complexes (Robinson et al, 2004;Yang et al, 2014Yang et al, , 2015 appears to be changing that view. It is now being argued that mantle sections of ophiolites either originate in, or were processed within, the Earth's mantle at depths as great as 600 km Xu et al, 2015;Griffin et al, 2016). Furthermore, these UHP phases are often found associated with ultra-reduced minerals: native metals, silicides, carbides, and nitrides (Dobrzhinetskaya et al, 2009;Xu et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

“…It is now being argued that mantle sections of ophiolites either originate in, or were processed within, the Earth's mantle at depths as great as 600 km Xu et al, 2015;Griffin et al, 2016). Furthermore, these UHP phases are often found associated with ultra-reduced minerals: native metals, silicides, carbides, and nitrides (Dobrzhinetskaya et al, 2009;Xu et al, 2015). Consequently, it is speculated that the mantle source regions of ophiolites must be ultra-reduced.…”

Section: Introductionmentioning

confidence: 99%

Ultra-high pressure and ultra-reduced minerals in ophiolites may form by lightning strikes

Ballhaus¹,

Wirth²,

Fonseca³

et al. 2017

Geochem. Persp. Let.

View full text Add to dashboard Cite

Since ultra-high pressure (UHP) minerals have been discovered in ophiolites from Tibet and the Polar Urals, it is speculated that the mantle sections of ophiolites may originate deep within the mantle. The UHP minerals are frequently found together with ultra-reduced silicides, carbides, and nitrides. Consequently, it is argued that the deep mantle, or at least domains within it, must be highly reduced, so reduced that practically all transition elements at depth are present in the metallic state. We find it problematic to rewrite the history of ophiolite complexes based on these observations and suggest we should search for alternative and more realistic modes of origin. Electric discharge experiments at >6000 K reported here show that the UHP and highly reduced phase assemblages may precipitate from plasmas. We argue that the mineral assemblages may originate by lightning strikes. As such, they may not record the origin and emplacement history of the mantle lithologies within which they occur.

show abstract

Origin of ultrahigh pressure and highly reduced minerals in podiform chromitites and associated mantle peridotites of the Luobusa ophiolite, Tibet

Cited by 89 publications

References 61 publications

Mineralogy and Geochemistry of the High‐Cr Podiform Chromitite from the Cuobuzha Ophiolite, Yarlung Zangbo Suture Zone, Western Tibet, China: Implication for its Origin

Mineralogy and Geochemistry of the High‐Cr Podiform Chromitite from the Cuobuzha Ophiolite, Yarlung Zangbo Suture Zone, Western Tibet, China: Implication for its Origin

Timing of Secondary Hydrothermal Alteration of the Luobusa Chromitites Constrained by Ar/Ar Dating of Chrome Chlorites

Ultra-high pressure and ultra-reduced minerals in ophiolites may form by lightning strikes

Contact Info

Product

Resources

About