SPP 1006 - Subproject: Mineralogical and geochemical studies of impact melt products from the Chesapeake Bay impact structure

Basic data for this project

Description

USGS and ICDP perform a drilling project into the 35 Ma old, ~85-km-sized submarine Chesapeake Bay impact structure, Virginia. This crater is source to the North American tektite strewn field and related microtektites in upper Eocene sediments. This proposal focuses on impact melt products (melt rocks, glass bombs/particles within impact breccias, tektites, microtektites, microkrystites) that originate during different stages of cratering. All named lithologies are supposed to occur at different geological settings in, around, or far off the Chesapeake crater. This gives a unique opportunity to ¿ study the so far rather unconstrained different mechanisms for the origin of the various melts, ¿ get insight into processes taking place in the vapor plume (mixing, high-temperature chemistry, redox conditions), ¿ derive the different cooling paths of impact glasses, and ¿ develop tools to distinguish microtektites from volcanic glass spherules. To reach this goals we intend to ¿ characterize melt and target lithologies by mineralogical and geochemical techniques, ¿ identify precursor rocks of impact glasses by geochemical and isotopic fingerprinting (Rb-Sr, Sm-Nd, REE with TIMS and LA-ICP-MS techniques), ¿ determine volatile content and redox state by a novel complementary approach combining a Directly coupled Evolved Gas Analysing System (DEGAS) with Electron Energy Loss Spectroscopy (EELS) on a transmission electron microscope (TEM).