Fifteen North Cascade Arc basalts and andesites were analyzed for Mg isotopes to investigate the extent and manner of crustal contributions to this magmatic system. The δ 26Mg of these samples vary from within the range of ocean island basalts (the lightest being −0.33 ± 0.07‰) to heavier compositions (as heavy as −0.15 ± 0.06‰). The observed range in chemical and isotopic composition is simila...

The Central Asian Orogenic Belt, or Altaids, is an amalgamation of volcanic arcs and microcontinent blocks that records a complex late Precambrian–Mesozoic accretionary history. Although microcontinents cored by Precambrian basement are proposed to play an integral role in the accretion process, a lack of isotopic data hampers volume estimates of newly produced arc-derived versus old-cratonic c...

Upper Jurassic and Lower Cretaceous bashal strata are preserved in a discontinuous belt along the inboard margin of the Alexander-WrangelliaPeninsular terrane (AWP) in Alaska and western Canada, on the outboard margin of terranes in the Canadian Cordillera accreted to North America prior to Late Jurassic time, and along the Cordilleran margin from southern Oregon to southern California. Nearly ...

[1] Garnet pyroxenites are the most common deep lithospheric xenolith assemblages found in Miocene volcanic rocks that erupted through the central part of the Sierra Nevada batholith. Elemental concentrations and isotope ratios are used to argue that the Sierra Nevada granitoids and the pyroxenite xenoliths are the melts and the residues/cumulates, respectively, resulting from partial melting/f...

U-Pb and Ar/Ar dates from the Talladega belt, southernmost Appalachians, provide insight into the timing and nature of pre-Alleghanian tectonism in this region. Low-grade metasedimentary rocks of the Talladega belt represent the outermost preserved portions of the southern Laurentian margin, thus recording the earliest orogenic events that affected the margin, in addition to later overprinting ...

We have attempted to constrain the depth(s) at which the main differentiation processes in arc lavas occur, using two main approaches; REE characteristics. The REE patterns of volcanic rock suites produced by crystal-liquid differentiation processes are sensitive to garnet or amphibole fractionation at deep or intermediate levels, respectively. Not surprisingly La/Yb increases with differentiat...

The late Precambrian Shadli Metavolcanics of SE Egypt constitute a slightly metamorphosed bimodal sequence that has been previously interpreted as manifesting volcanic activity at an island arc. We report the first Rb-Sr geochronologic, trace element (including REE), and Nd isotopic data for these rocks. Two types of basalt are recognized, the stratigraphically lower suite having compositions l...

While most volcanic arcs show a distinctive spatial relationship to subducting plates, there are many examples where volcanoes occur in anomalous locations. These commonly also geochemically relative the composition of more typical subduction-related rocks. Using Holocene South America as case study, we document and geochemical patterns along Andean belt. To determine whether variations anomalo...