Potassium-rich magmatism from a phlogopite-free source

Abstract

This file contains three figures and six tables. ANALYTICAL METHODS Major elements: Whole-rock major element compositions of the phyllite and dunite were determined by X-ray fluorescence spectrometry (XRF) using a Philips MagiXPRO spectrometer on fused discs. Major element compositions of melts and minerals were obtained by CAMECA SX-100 electron microprobe (EMP) at the Department of Earth and Planetary Sciences, Macquarie University, with operating conditions of generally 15 kV accelerating voltage and 20 nA beam current. Counting times were 10 s for peaks, and 5 s for each background. The peaks were calibrated by measurements of standards (natural minerals and synthetic oxides). For mineral phases a beam diameter of 1 μm was used, which was increased to 5 μm for the analysis of quenched melt areas. Trace elements: Trace elements were analysed by laser ablation-inductively coupled plasmamass spectrometry (LA-ICP-MS) at Macquarie University. For phyllite and dunite, rock powders were melted to form glass beads without any fluxing agent on an iridium strip heater in an argon atmosphere and analyzed by laser sampling of the glasses. All analyses used 266 nm Nd-YAG laser coupled to an Agilent 7500ce ICP-MS. The laser was operated at a repetition rate of 5 Hz, with laser energy at the sample site of 5-6 J/cm2, allowing data collection from individual grains in polished thick sections (up to 80 μm thickness) for at least 40 s. Nitrogen was mixed with helium before ablated materials were introduced into the ICP-MS. Data were measured for 60 s plus 30 s background with beam sizes of 30 μm and 50 μm for most samples, 80 μm for some large-grained melt pools, 15 μm and 20 μm for a few small-grained accessory phases and melt samples from experiments. 29 Si and 44 Ca were used as the internal standards applying the Si and Ca concentrations previously determined by electron microprobe. For calibration, NIST SRM 610 was analysed at the beginning and after every 20 measurements on the unknown samples. The time-resolved signal was processed using the program GLITTER 4.4.1 (www.glitter-gemoc.com, Macquarie University), applying the preferred values for NIST SRM 610 reported in the GeoReM database (http://georem.mpch-mainz.gwdg.de/) (Jochum et al., 2011). Analytical uncertainty (one sigma) for a spot analysis or line scan was less than 10 %. During each run the basaltic USGS BCR-2G reference glass was analysed as an unknown to monitor accuracy and reproducibility of the analyses. EXPERIMENTAL METHOD All experiments were performed in a 0.5-inch piston-cylinder apparatus based on a modified Boyd-England design at Macquarie University (Boyd and England, 1960). Furnace assemblies (12.7 mm diameter) were made of graphite with cylindrical talc outer sleeve and pyrex® inner sleeve and BN inserts. Temperatures were measured using Pt-Pt 90 Rh 10 thermocouples and automatically controlled by an Electromax V single loop controller. Samples were welded into a 4 by 4 mm Ag 70 /Pd 30 capsule with a wall thickness of 0.2 mm, minimizing iron loss...

Hybridization Melting Between Continent‐Derived Sediment and Depleted Peridotite in Subduction Zones

“… Note . This table was adapted from Wang, Foley, et al (). Phases in italics are accessory phases present in the run products in the range of 0–1 vol%.…”

“…M, melt; Ol, olivine; Coe, coesite; Chr, chromite; Opx, orthopyroxene; Alm‐grt, almandine‐rich garnet; Prp‐grt, pyrope‐rich garnet. Adapted from Wang, Foley, et al ().…”

40Ar-39Ar geochronology and petrogenesis of postcollisional trachytic volcanism along the İzmir-Ankara-Erzincan Suture Zone (NE, Turkey)*

“…There are different geotectonic scenarios for the generation of the metasomatic source regions that give rise to high-K magmatism, such as (i) reaction of accreted and recycled terrigenous sediments (Gao et al, 2007;Prelević et al, 2008Prelević et al, , 2013Wang et al, 2017) together with highpressure metamorphic rocks (blueschist) (Tommasini et al, 2011) with peridotitic lithologies in fossil mantle wedge settings and (ii) direct melting of continental crust during the continental collision and subduction (Zhao et al, 2009;Ersoy et al, 2010). Postcollisional magmatic units along the Eastern Mediterranean generally mimic the arc-like geochemical signatures that are heavily influenced by the melts/fluids transported from the subducted slab (altered oceanic crust) together with subducted sediments (Ersoy et al, 2010;Kirchenbaur et al, 2012;Prelević et al, 2013).…”

“…Petrogenesis of postcollisional trachytic rocks and potassic magmatism do not have a unique mode of generation in all cases, and the process can be governed by different orders of partial melting, fractional crystallization/assimilation, and magma mixing depending on the tectonomagmatic behavior of the studied systems (e.g., Conticelli et al, 2009). On the other hand, postcollisional lithospheric domains are generally already metasomatized by the previous subduction, collision, and accretion event; thus, the source area and the generation of the trachytic/potassic volcanism can be strongly influenced by different and heterogeneous components (e.g., Prelević et al, 2013;Gülmez et al, 2016;Wang et al, 2017).…”

Some remarks on the nature of mantle metasomatism beneath western Anatolian–Aegean region: Contrasting isotopic signatures recorded in the Miocene lavas from the Söke Basin

“…Radiogenic imprints of recycled material as a mantle source characteristic in a convergence setting most probably reflect the effects of incorporation of crust‐derived material into a more depleted mantle. The process envisaged may be, to some extent, similar to that proposed in some recent experimental studies, where interactions between previously depleted wedge peridotite and sediment‐derived melts have been shown to have the capacity to create a hybrid source that can undergo partial melting at some stage to produce potassium‐rich melts of mantle origin with trace element and radiogenic isotopic signatures that reflect the strong influence of subducted crustal material (Wang et al, ). For the case of the lavas form western Anatolia, the mantle component that formed in this way is shown to have significantly high 87 Sr/ 86 Sr (>0.7060) and low 143 Nd/ 144 Nd (<0.5126) values, with a relatively restricted range of 206 Pb/ 204 Pb values (18.6–19.0), and it appears to have been involved (to a variable extent) in generating the majority of the Cenozoic magmatic suites in this region (Figure ).…”