Contemporaneous late cretaceous calc-alkaline and alkaline magmatism in Central Anatolia, Turkey: oxygen isotope constraints on petrogenesis

A wide variety of rock types were produced by the latest Cretaceous magmatism in the Central Anatolian Crystalline Complex. These rocks can be divided into three distinct units: (i) calc-alkaline, (ii) subalkaline/transitional, and (iii) alkaline. The calc-alkaline rocks are mainly metaluminous (I-type) ranging from monzodiorite to granite. The subalkaline/transitional rocks are also metaluminous (I-type) ranging from monzonite to granite. The alkaline rocks are mainly peralkaline (A-type), ranging from feldspathoid-bearing monzosyenite to granite. Whole-rock oxygen isotope data from the complex have a considerable range of δ18O values between 6.5‰ and 14.8‰. Initial 87Sr/86Sr versus 143Nd/144Nd ratios, and both ratios versus δ18O values diagrams show that the intrusive rocks are derived from a subduction-modified mantle and also have experienced fractional crystallisation coupled with crustal assimilation. Delamination of a thermal boundary layer, and/or slab breakoff is the likely mechanisms for the initiation of the diverse magmatism in the complex

Sourcing the quartz at Newgrange, Bru na Boinne, Ireland

No abstract available

⁸⁷Sr/⁸⁶Sr: A new discriminant for provenancing neolithic porcellanite artifacts from Ireland

Antrim porcellanite (thermally metamorphosed Tertiary laterite) was the most common raw material used in the production of stone implements during the Neolithic in Ireland and was worked at two localities in North Antrim: Tievebulliagh, near Cushendall and Brockley on Rathlin Island. Attempts have been made to provenance material from these two known sources, the most successful to date being the use of geochemical data (Sr and Yppm). Here we present a new geochemical discriminant-Sr isotopic data-which reveal that Tievebulliagh and Brockley porcellanites are distinctive. Present-day 87Sr/86Sr ratios form two discrete groupings ranging from 0.705894±25-0.706443±24 at Tievebulliagh and 0.704088±27-0.704587±25 at Brockley. A coherent relationship between 87Sr/86Sr and Sr (ppm) reiterates the use of Sr content as a discriminant and illustrates the geochemical variability of Sr between these two sources. Although this is a destructive technique, 87Sr/86Sr represents the best discriminant to date for Antrim porcellanites and will enable definitive provenancing of porcellanite artifacts from Ireland with important archaeological implications