New geochronologic and paleomagnetic data from the North American Midcontinent Rift (MCR) reveal synchronous emplacement of Beaver River diabase, anorthosite xenoliths within it, Greenstone Flow—one largest lava flows on Earth. A U-Pb zircon date 1091.83 0.21 Ma (2) one is consistent with cumulate forming as part MCR provides a maximum age constraint for diabase. Paired minimum cross-cutting Si...

During Leg 185 two deep-water sites will be drilled, one seaward of the Mariana Trench (Ocean Drilling Program Hole 801C) and one seaward of the Izu-Bonin Trench (Site BON8A). The primary objectives are to investigate sediment subduction along this arc-trench system and to characterize the chemical fluxes during alteration of the oceanic crust. Despite the simple setting and shared subducting p...

The cryosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences underlying the modern McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line position and main icestream flow directi...

The Southern Sierra Nevada mountain range rapidly uplifted at ≈3.5 Ma simultaneously with a pulse of basaltic volcanism. Xenoliths recovered from volcanics indicate that the range lost a dense crustal root after the Miocene. The vertical motions and removal of the root have been linked to a fast seismic velocity anomaly that extends ≈200 km into the mantle but is offset to the west of the range...

Pitchblende mineralization was studied in the younger granite samples collected from Gabal Gattar, north Eastern Desert, Egypt using electron scanning microscope (ESM) and electron probe microanalyses (EPMA). This study revealed that this pitchblende contains significant Zr content reaching up to (66.80% ZrO2), which suggests that volcanic rocks were probably the source of such a deposit. High ...

The Wadi Hodein area contains a wide variety of late Precambrian igneous and metamorphic rocks, represented by gneisses, serpentinites, metagabbros, metasediments, metavolcanics, metagabbro-diorite, granodiorite and granitoids. The Wadi Hodein metavolcanics (WHV), including G. Khashab and G. El Anbat, represent one of the significant metavolcanic suites in the southern part of the Nubian Shield...

Ž . Previous research on sea floor Fe III oxyhydroxide deposits has focused primarily on deep-sea, hydrothermal systems found along volcanically active portions of the mid-ocean ridges and on hydrogenetic deposits formed in deep basins and along continental shelves. There is, however, not much known about their formation in shallow-water settings associated with volcanic islands. The hydrotherm...

reservas, similares procesos metalogenéticos habrian actuado en el Paleozoico Inferior del Brea. La deformación y el metamorfisme regional hercinicos no han actuado en este sector como un importante reconcentrador de menas, y la mayor parte de indicios epigenéticos Many mineralizations, showings and geochemical anomalies de edad tardihercinicaestán relacionados alas células hidrotermales have b...

The geochemical discriminate diagrams help to distinguish the volcanics recovered from different tectonic settings but these diagrams tend to group the ocean floor basalts (OFB) under one class i.e., as mid-oceanic ridge basalts (MORB). Hence, a method is specifically needed to identify the OFB as normal (N-MORB), enriched (E-MORB) and ocean island basalts (OIB). We have applied Artificial Neur...

Plio–Pleistocene (3.4–0.125 Ma) post-plateau magmatism in the Meseta del Lago Buenos Aires (MLBA; 46.7jS) in southern Patagonia is linked with the formation of asthenospheric slab windows due to ridge collision along the Andean margin f 6 Ma ago. MLBA post-plateau lavas are highly alkaline (43–49% SiO2; 5–8% Na2O+K2O), relatively primitive (6–10% MgO) mafic volcanics that have strong OIB-like g...