Introduction: Crystallization ages of lunar impact melt rocks provide the primary evidence for a spike in the impact flux at ~3.9 Ga. Here we report U-Pb isotopic ages of accessory phases (apatite, zirconalite) in lunar melt breccia 67955 that confirm a crystallization age of ~4.2 Ga and reveal a younger overprint possibly related to entrainment of the breccia by one or more younger basins such...

Introduction: The Chesapeake Bay impact structure, 35 Myr old and 85 km in diameter, is one of the largest and best preserved impact structures on Earth [1]. The structure was drilled in the central part at Eyreville in 2005-2006 during an ICDP-USGS drilling project. Three drill cores (Eyreville A, B, and C), intersecting the impact structure to a total depth of 1766 m, were recovered within th...

Using some new processing of the multichannel sonic (MCS) log data from Site 418A, the resulting P, S, and Stoneley wave velocity estimates and apparent attenuation were integrated with the natural gamma, spectral gamma, resistivity, neutron, density, and caliper logs and core lithology information for interpretation of lithologic cycles and possible paleo fluid flow intervals. These data indic...

Sharply defined veins in :stockworks and siliceous breccia matrix contain metallic mineral assembhges and follow a number of subparallel trends within and marginal to a ] p tassium-feldspar porphyritic dacite. The .porphyritic dacite and metal-bearing veins and breccias exhibit both con-. formable and crosscutting relationships with andesite and dacite country rocks of the Hazelton Group. Vein ...

Samples of basalt were collected during the Rapid Response cruise to Loihi seamount from a breccia that was probably created by the July to August 1996 Loihi earthquake swarm, the largest swarm ever recorded from a Hawaiian volcano. Po–Pb dating of two fresh lava blocks from this breccia indicates that they were erupted during the first half of 1996, making this the first documented historical ...

An assemblage of hydrous, Cl-bearing alteration-induced minerals is present within 150 m of footwall-style Cu–Ni–PGE sulfide mineralization hosted by the Sudbury Breccia at the Fraser Copper zone, Fraser mine, Onaping–Levack area, Ontario. The pyroxene hornfels to hornblende hornfels contact-metamorphic aureole of the Sudbury Igneous Complex (SIC) contains less than 15 modal % hydroxysilicates....

The rare earth elements (REE) are composed of the Lanthanide Series of 15 elements with atomic numbers (57) through (71) and yttrium (39). Because of their geochemical behavior, REE rarely form their own minerals and more commonly are found incorporated within the structure of other minerals. There is growing concern over the economical availability of REE because of their diverse and expanding...

Introduction: Gravity data provide important constraints on morphometry of impact structures and on the crustal response to the impact process [1-3]. Such data can provide insight that may not be obtainable from surface geologic mapping and may not be quickly or cheaply obtained by other geophysical means. The gravity data can be used to constrain the dimensions of a completely to partly buried...