Metasomatic interactions between slab-derived melts and depleted mantle: Insights from xenoliths within Monglo adakite (Luzon arc, Philippines)

Abstract

somatic interactions between slab-derived melts and depleted mantle: Insights from xenoliths within Monglo adakite (Luzon arc, Philippines). Lithos, Elsevier, 2008, 103 (3-4) AbstractThe Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon arc crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.

Geochronology and geochemistry of late Archean adakitic plutons from the Taishan granite–greenstone Terrain: Implications for tectonic evolution of the eastern North China Craton

“…In other words, the Yishui HSA magmas were generated by melting of a basaltic slab located deeper in the mantle than during the generation of the Taishan HSA magmas; this in turn allowed substantial interaction between the Yishui HSA magmas and the overlying peridotite mantle (see Martin et al, 2005). The discovery of adakitic glass inclusions in olivine from mantle peridotite xenoliths from the Batan subduction zone (Schiano et al, 1995), the Quaternary Cello Del Fraile basalt, southernmost south America (Kilian and Stern, 2002) and mafic-ultramafic xenoliths in the Monglo adakites from the Luzon arc, Philippines (Gregoire et al, 2008) confirm interaction between slab melts and peridotite. In comparison, the Zoucheng HSA magmas, with their higher SiO 2 concentrations and lower Mg numbers and Cr and Ni concentrations, might have been derived from partial melting of the downgoing basaltic slab at shallower depths and undergone little or no interaction with the overlying peridotitic mantle during ascent, explaining the similarity between their compositions and the experimental melts shown in Fig.…”

“…Increasing numbers of adakites or adakitic rocks have been described over the entire geological timescale, from Archean granite-greenstone belts to modern-day occurrences associated with subduction zones around the Pacific Rim (e.g., Kay and Kay, 1993;Peacock et al, 1994;Stern and Kilian, 1996;Jego et al, 2005;Smithies et al, 2005;Zhou et al, 2006;Manya et al, 2007;Naqvi and Rana Prathap, 2007;Zhao et al, 2007;Gregoire et al, 2008;Naqvi et al, 2009). Actually, it is difficult to relate older adakites and associated suites formed in extinct magmatic systems to tectonic settings, particularly within the Archean.…”

Zincian chromite inclusions in diamonds: Possibility of deep recycling origin

“…They are mainly associated with olivine, pyroxenes, plagioclase, graphite, and troilite, Smaller symbols indicate spinels with less than 1 wt% ZnO. The plots show chromian spinels in mantle peridotites (dots, encircled) (Downes et al, 2004;Rudnick et al, 2004;Gregoire et al, 2008) for reference. Open circles indicate zincian chromite inclusions in diamonds (Meyer and Boyd, 1972).…”

“…The mantle peridotite, which has been metasomatized under mantle conditions to various extents, contains spinels having low amounts of Zn (<0.4 wt% ZnO) (e.g., Downes et al, 2004;Rudnick et al, 2004;Gregoire et al, 2008) (Fig. 1).…”

Re–Os isotopic composition of peridotitic sulphide inclusions in diamonds from Ellendale, Australia: Age constraints on Kimberley cratonic lithosphere

“…Whereas depleted harzburgitic compositions in the SCLM are due dominantly to melt depletion events, lherzolitic compositions in the SCLM may be due to refertilisation of peridotite by metasomatic fluids introduced either through subduction or localised metasomatic alteration events in the mantle (Grégoire et al, 2003(Grégoire et al, , 2005(Grégoire et al, , 2008Simon et al, 2007). At Ellendale, subduction processes are not supported, since the sulphide inclusions in the diamonds would have inherited high initial 187 Os/ 188 Os ratios from fluids with a radiogenic Os signature introduced from the subducting plate, as has been shown for the Panda diamonds on the Slave craton by Westerlund et al (2006).…”