Controls on PGE fractionation in the Emeishan picrites and basalts: Constraints from integrated lithophile–siderophile elements and Sr–Nd isotopes

Li, Chusi; Tao, Yan; Qi, Liang; Ripley, Edward M.

doi:10.1016/j.gca.2012.04.046

Cited by 72 publications

(14 citation statements)

References 76 publications

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“…The estimated PGE concentrations for the parental magma of the Hongqiling No. 7 intrusion are much lower than those in the picritic basalts of the Siberian Trap (e.g., Lightfoot and Keays, 2005) and the picrites of the Emeishan large igneous province (e.g., Wang et al, 2007;Li et al, 2012b).…”

Section: Possible Factors Controlling the Formation Of Pge-depleted Smentioning

confidence: 94%

Origin of PGE-Depleted Ni-Cu Sulfide Mineralization in the Triassic Hongqiling No. 7 Orthopyroxenite Intrusion, Central Asian Orogenic Belt, Northeastern China

Wei¹,

Wang²,

Li³

et al. 2013

Economic Geology

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The ~216 Ma Hongqiling No. 7 intrusion is located in the southern margin of the Central Asian orogenic belt, northeastern China. It was the second largest Ni producer after Jinchuan in China. The intrusion crops out in an area of ~0.013 km 2 on the surface. It intruded gneisses and marbles of the Paleozoic Hulan Formation. The intrusion is mainly composed of orthopyroxenite (~95 vol %), with minor harzburgite and norite. Over 90 vol % of the intrusion contains disseminated, net-textured or massive sulfides. The bulk sulfide ores (recalculated to 100% sulfide) have low average PGE concentrations (5.6 ppb Os, 3.1 ppb Ir, 4.7 ppb Ru, 2.2 ppb Rh, 31 ppb Pt, and 11 ppb Pd) and high Cu/Pd ratios (3 × 10 5 −3 × 10 7 ), consistent with the compositions of sulfide liquids segregated from PGE-depleted magma. Olivine composition (Fo <86 mol %) indicates a fractionated parental magma. Back calculation shows that the parental magma was possibly derived by olivine fractionation from a primary magma containing ~16 wt % MgO. Numerical modeling indicates that PGE depletion in the parental magma of the Hongqiling No. 7 intrusion was due to previous sulfide segregation in the staging chamber. Whole-rock data show light rare earth element (REE) enrichments, negative Nb-Ta anomalies, and positive eNd (t = 216 Ma) values from 3 to 5, which can be explained by mixing of a mantle-derived magma with a granitic melt formed by magma underplating in the crust. The gOs (t = 216 Ma) values of sulfide ores vary from 50 to 187. The highly variable gOs(t) values coupled with similar eNd(t) values indicate preferential assimilation of crustal sulfides during magma rock interaction. Based on the observations, we propose that the parental magma of the Hongqiling No. 7 intrusion formed by contamination of mantle-derived, S-undersaturated magma by crustally derived granitic melt, together with olivine crystallization, in a staging chamber. The contaminated magma became PGE depleted due to sulfide segregation in response to crustal contamination. The PGE-depleted magma became S undersaturated again during ascent due to the negative effect of pressure on the maximum solubility of sulfur in magma. Upon arrival near the present level of the Hongqiling No. 7 intrusion a second event of sulfide segregation took place due to addition of crustal sulfides from immediate country rocks. The immiscible sulfide liquids and orthopyroxene crystallizing from the magma were retained in a dynamic conduit to form the ore-bearing intrusion while much of the magma left the conduit to form some of the nearby sulfidepoor intrusions. We suggest future exploration in the region to focus on olivine-bearing and orthopyroxenedominant intrusions with ages similar to that of the Hongqiling No. 7 intrusion.

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Section: Possible Factors Controlling the Formation Of Pge-depleted Smentioning

confidence: 94%

Origin of PGE-Depleted Ni-Cu Sulfide Mineralization in the Triassic Hongqiling No. 7 Orthopyroxenite Intrusion, Central Asian Orogenic Belt, Northeastern China

Wei¹,

Wang²,

Li³

et al. 2013

Economic Geology

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“…Wang et al (2011) determined HSE concentration in a suite of intrusive rocks and low-magnesian lavas, and concluded that fractionation crystallization under either sulfur-undersaturated or sulfur-saturated conditions controlled the HSE behavior. However, there have been few systematic studies of the HSE in highly magnesian lavas from the ELIP (i.e., MgO > 12 wt.%; Li et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Chemical heterogeneity of the Emeishan mantle plume: Evidence from highly siderophile element abundances in picrites

Wang

Ren

et al. 2014

Journal of Asian Earth Sciences

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a b s t r a c tHighly magnesian lavas or picrites have the potential to preserve important information about the origin and thermochemical state of the mantle source(s) of large igneous provinces. We have conducted a comprehensive study of highly siderophile element (HSE) concentrations in picrites from the ca. 260 Ma Emeishan large igneous province. We show that HSE abundances in the Emeishan picrites are greater than those in mid-ocean ridge basalts (MORBs) and parental melts of Hawaiian picrites, but are similar to those in komatiites. The picrites have two types of C1-normalized HSE patterns: (a) type 1, as represented by the Muli picrites is similar to that of the primitive upper mantle; (b) type 2, as represented by the Dali picrites resembles East Greenland and Iceland picrites. Pt/Ir and Pd/Ir ratios in the type 2 picrites are higher than those in type 1 picrites. The primary melt compositions of the studied samples have been estimated by back-addition of equilibrium olivine. The calculated HSE abundances of the parental liquids of the Dali and Muli picrites are higher than those of the parental melts to Hawaiian picrites. Along with previously published isotopic data, our study provides further evidence for chemical heterogeneity of the Emeishan mantle plume.

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“…4a). Olivine grains in both the dunites and lherzolites have very low CaO contents (0.03 to 0.16 wt.%), much lower than the olivine grains (CaO = 0.25 to 0.51 wt.%) in the picrites of the ELIP (Li et al, 2012) at the same Fo values (89 to 83) (Fig. 4b).…”

Section: Mineral Chemistrymentioning

confidence: 95%

“…Low-Ca olivine grains are in fact common in the mafic-ultramafic intrusions of the ELIP, such as those in the Ni-Cu-(PGE) sulfidebearing Jinbaoshan, Limahe and Nantianwan intrusions and the Fe-Ti oxide-bearing Panzhihua and Hongge intrusions Pang et al, 2008a;Tao et al, 2008;Pang et al, 2009;Wang et al, 2012) and mafic dikes in the Funing region (Wang et al, 2011). Olivine crystals in these mafic-ultramafic intrusions/dikes have b0.21 wt.% CaO (mostly b0.15 wt.%, i.e.,~1050 ppm Ca), whereas the olivine phenocrysts in the picrites of the ELIP commonly have N0.25 wt.% CaO (~1785 ppm Ca) at similar Fo contents (Li et al, 2012) (Fig. 4b).…”

Section: Cumulate Origin Of the Abulangdang Ultramafic Intrusionmentioning

confidence: 98%

“…8). The high-Ti flood basalts of the ELIP are thought to have been derived from a parental magma formed by low degrees of partial melting of an OIB-like, enriched mantle source (Wang et al, 2007;Zhou et al, 2008), therefore, significant depletion of Os-Ir-Ru in the high-Ti flood basalts is possibly due to the presence of trace phases such as Os-Ir-Ru alloys and PGE sulfides in the mantle (Li et al, 2012). However, the conjugate PGE profiles between the rocks of the Abulangdang intrusion and the high-Ti flood basalts likely reflect the compatibility of IPGE (Os, Ir and Ru) in chromite and trace phases associated with olivine during fractionation.…”

Section: Fractionation Of Primitive High-ti Picritic Magmasmentioning

confidence: 99%

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Geochemistry of the Abulangdang intrusion: Cumulates of high-Ti picritic magmas in the Emeishan large igneous province, SW China

et al. 2014

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Controls on PGE fractionation in the Emeishan picrites and basalts: Constraints from integrated lithophile–siderophile elements and Sr–Nd isotopes

Cited by 72 publications

References 76 publications

Origin of PGE-Depleted Ni-Cu Sulfide Mineralization in the Triassic Hongqiling No. 7 Orthopyroxenite Intrusion, Central Asian Orogenic Belt, Northeastern China

Origin of PGE-Depleted Ni-Cu Sulfide Mineralization in the Triassic Hongqiling No. 7 Orthopyroxenite Intrusion, Central Asian Orogenic Belt, Northeastern China

Chemical heterogeneity of the Emeishan mantle plume: Evidence from highly siderophile element abundances in picrites

Geochemistry of the Abulangdang intrusion: Cumulates of high-Ti picritic magmas in the Emeishan large igneous province, SW China

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