It is generally accepted that progressive cooling of global climate since the Late Cretaceous results from decreasing partial pressure of atmospheric CO2 (pCO2). However, details on how and why the carbon cycle evolved and how it would affect pCO2 have not been fully resolved. While the long-term decline of pCO2 might be caused by the decrease of volcanic degassing through the negative feedback...

We present a quantitative assessment of the thermal and dynamic response of an amphibolitic lower crust to the intrusion of basaltic dike swarms in an arc setting. We consider the effect of variable intrusion geometry, depth of intrusion, and basalt flux on the production, persistence, and interaction of basaltic and crustal melt in a stochastic computational framework. Distinct melting and mix...

On Leg 25 of the Deep Sea Drilling Project five holes penetrated basement, and a total of approximately 12.7 meters of basalt were recovered. We have measured compressional and shear wave velocities to hydrostatic pressures of 6 kb in representative samples of basalt from each hole and a relatively high density limestone from Site 249. In addition, compressional wave velocities are reported for...

In order to further constrain the timing of Aleutian Arc initiation as well its early evolution, an extensive 40Ar/39Ar dating and geochemical (major selected trace elements) campaign (40 samples) lower units ridge has been carried out on samples dredged from deep fore-arc canyons rear-arc tectonic structures. The new dataset slightly increases minimum inception age for system, with two oldest ...

Samples produced in piston cylinder experiments were used to document the thermal isotopic fractionation of all the major elements of basalt except for aluminum and the fractionation of iron isotopes by chemical diffusion between a natural basalt and rhyolite. The thermal isotopic fractionations are summarized in terms of a parameter Xi defined as the fractionation in per mil per 100 C per atom...

Abstmct: Island arc lavas from New Britain and the Marianas have 143 Nd/144 Nd similar to other oceanic basalts and distinctly different from continental flood basalts and thus appear to be derived from a high Sm/Nd, light-REE-depleted reservoir. Consideration of both Nd and Sr isotopes suggests seawater involvement in the generation of some island arc lavas and thus indicates that they may be ...

Silicic volcanic rocks are associated with most, if not all, continental ×ood basalt provinces and volcanic rifted margins, where they can form substantial parts of the eruptive stratigraphy and have eruptive volumes >104 km3. Poor preservation of silicic volcanic rocks following kilometer-scale uplift and denudation of the volcanic rifted margins, however, can result in only deeper level struc...

In the central Oregon Cascades, extension of the arc has promoted eruption of primitive basalts that are of three types, calcalkaline (CAB), low-K tholeiitic (LKT) and rare absarokitic (ABS) in the forearc. Based on a comparison with the distribution of primitive magma types and their Sr/Sr and Nd/Nd isotopic signature in the Cascades, we divide the arc into four segments that correspond to dis...