Petrology and Geochemistry of Eclogite Xenoliths from the Colorado Plateau: Implications for the Evolution of Subducted Oceanic Crust

Usui, Tomohiro; Nakamura, Eizo; Helmstaedt, Herwart

doi:10.1093/petrology/egi101

Cited by 71 publications

(47 citation statements)

References 96 publications

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“…They are a major repository of Sr, Pb, U, Th, and LREE and their trace element ratios (Brunsmann et al, 2000;Feineman et al, 2007;Frei et al, 2004;Hickmott et al, 1992;Spandler et al, 2003;Usui et al, 2006, and references therein), although not conclusive, seem to match those required by the SALATHO component. For example, Spandler et al (2003) reported trace element content of lawsonite from blueschist facies pelitic samples occurring in the New Caledonia orogenic belt with La = 119 ppm, Sm = 77 ppm, Th = 80 ppm, and U = 7 ppm (i.e.…”

Section: Decoding the Salatho Component Within Tethyan Realm Geodynammentioning

confidence: 95%

The Th/La and Sm/La conundrum of the Tethyan realm lamproites

Tommasini

Avanzinelli

Conticelli

2011

Earth and Planetary Science Letters

142

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Pb end-member that can be reconciled with the SALATHO component. This end-member requires a history of high timeintegrated κ ( 232 Th/ 238 U) and low time-integrated μ ( 238 U/ 204 Pb) and ought to be older than some hundreds of million years. We propose a multi-stage process for the formation of the mantle sources of the Tethyan Realm Lamproites related to the tectonic mélange domains (i.e. chaotic mixture of depleted peridotite, basalt, and sediment) accreted to the Eurasia plate during the collisional events of the northward drifting continental slivers from Gondwana. In a first stage, the mélange domains experienced high P and low T metamorphism with segregation and stabilisation of lawsonite and zoisite/epidote veins, which potentially match the geochemical characteristics required by the SALATHO component. Successively, the subduction of the Neotethys and Alpine Tethys oceanic plates produced normal K 2 O-rich sediment melts that migrated through the mantle wedge and metasomatised the depleted lithospheric mantle blocks within the chaotic mélange, forming a clinopyroxene-phlogopite vein network. Eventually, the Tertiary orogenic belt collapses triggered the onset of low-degree melting of the low-solidus fractions within the mélange domains, producing lamproitic magmas.

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Section: Decoding the Salatho Component Within Tethyan Realm Geodynammentioning

confidence: 95%

The Th/La and Sm/La conundrum of the Tethyan realm lamproites

Tommasini

Avanzinelli

Conticelli

2011

Earth and Planetary Science Letters

142

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“…Stabilisation of lawsonite and zoisite/epidote at high P and low T within the subducted oceanic crust is the most likely process responsible for the SaLaThO geochemical component. These minerals are the major repository of Sr, Pb, U, Th, and LREE in such rocks (e.g., Spandler et al, 2003;Usui et al, 2006;Martin et al, 2014, and references therein). The lack of the SaLaThO geochemical component in the mafic high-MgO ultrapotassic rocks of the Roman magmatic province is a clear evidence for the arrival in the Central Mediterranean subcontinental lithospheric mantle of a new crustal-derived K-rich metasomatic agent after SaLaThO exhaustion.…”

Section: The Salatho Geochemical Paradoxmentioning

confidence: 99%

The role of carbon from recycled sediments in the origin of ultrapotassic igneous rocks in the Central Mediterranean

Conticelli

Avanzinelli

Ammannati

et al. 2015

Lithos

103

102

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The Central Mediterranean region is one of the most important areas on Earth for studying subduction-related potassic and ultrapotassic magmatism, derived from partial melting of the metasomatised lithospheric mantle wedge. In this region, leucite-free (i.e., lamproite) and leucite-bearing (i.e., kamafugite, leucitite, and plagioleucitite) ultrapotassic rocks closely occur, in a time-related progression, linked to the evolution of both the mantle source and the regional tectonic regime. Time- and space-related magmatism migration followed the roll-back of the subducting slab and the anticlockwise drift of the Italian Peninsula. Leucite-free silica-rich lamproites are restricted to the early stage of magmatism and are associated with ultrapotassic shoshonites and high-K calc-alkaline volcanic rocks. Leucite-bearing (i.e., Roman Province) rocks are erupted consistently later than lamproite-like and associated shoshonitic rocks, with post-leucititic volcanism occurring in the late stage of volcanic activity with eruption of alkali-basaltic to latitic and trachytic rocks, often after major caldera-forming events. Present-day ultrapotassic volcanism is restricted to the Neapolitan area. Central Mediterranean potassic and ultrapotassic rocks are extremely enriched in incompatible trace elements with variable fractionation of Ta, Nb, and Ti in comparison to Th and large ion lithophile elements (LILE). They are also variably enriched in radiogenic Sr and Pb and unradiogenic Nd. The main geochemical and isotopic signatures are consistent with sediment recycling within the mantle wedge via subduction. A twofold metasomatism, induced by the recycle of pelitic sediments and dehydration of lawsonite-bearing schists generates the early metasomatic events that enriched the mantle wedge from which leucite-free ultrapotassic rocks (i.e., lamproite) were generated. Recycling of carbonate-rich pelites played an important role in the shift to silica-undersaturated ultrapotassic rocks (kalsilite- and leucite-bearing) of the classic ‘Roman province’

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“…Xenoliths from the Colorado Plateau, USA: Xenoliths of jadeitite, omphacite, zoisite-eclogite, kyanite-eclogite, and lawsonite eclogite occur in kimberlitic pipes at Garnet Ridge in the Colorado Plateau; they may have been generated by Cretaceous subduction of the Franciscan Complex in western California, and carried beneath the North American continent on the Fallon plate (Usui et al, 2003(Usui et al, , 2006. Lawsonite eclogite with zircon U-Pb ages of 81-33 Ma has a MORB-like bulk-rock composition, and contains Grt + Omp ($43 mol% Jd) + Lws + Rt ± Phe ($3.8 Si pfu) + Coe.…”

Section: Recently Recognized Uhp Terranesmentioning

confidence: 99%