Mafic slab melt contributions to Proterozoic massif-type anorthosites.

Massif-type anorthosites, enormous and enigmatic plagioclase-rich cumulate intrusions emplaced into Earth's crust, formed in large numbers only between 1 and 2 billion years ago. Conflicting hypotheses for massif-type anorthosite formation, including melting of upwelling mantle, lower crustal melting, and arc magmatism above subduction zones, have stymied consensus on what parental magmas crystallized the anorthosites and why the rocks are temporally restricted. Using B, O, Nd, and Sr isotope analyses, bulk chemistry, and petrogenetic modeling, we demonstrate that the magmas parental to the Marcy and Morin anorthosites, classic examples from North America's Grenville orogen, require large input from mafic melts derived from slab-top altered oceanic crust.

Oceanic intraplate explosive eruptions fed directly from the mantle.

Constraining the volatile content of magmas is critical to our understanding of eruptive processes and their deep Earth cycling essential to planetary habitability [R. Dasgupta, M. M.

Postmelting hydrogen enrichment in the oceanic lithosphere.

The large range of HO contents recorded in minerals from exhumed mantle rocks has been challenging to interpret, as it often records a combination of melting, metasomatism, and diffusional processes in spatially isolated samples. Here, we determine the temporal variations of HO contents in pyroxenes from a 24-Ma time series of abyssal peridotites exposed along the Vema fracture zone (Atlantic Ocean). The HO contents of pyroxenes correlate with both crustal ages and pyroxene chemistry and increase toward younger and more refractory peridotites.

Pliocene eclogite exhumation at plate tectonic rates in eastern Papua New Guinea.

As lithospheric plates are subducted, rocks are metamorphosed under high-pressure and ultrahigh-pressure conditions to produce eclogites and eclogite facies metamorphic rocks. Because chemical equilibrium is rarely fully achieved, eclogites may preserve in their distinctive mineral assemblages and textures a record of the pressures, temperatures and deformation the rock was subjected to during subduction and subsequent exhumation. Radioactive parent-daughter isotopic variations within minerals reveal the timing of these events.

Social reinforcement of substance abuse treatment aftercare participation: Impact on outcome.

Although adherence to aftercare therapy in substance abuse treatment is associated with improved outcome, little research has explored the effects of adherence interventions on outcome. We compared 20 graduates of our 28-day intensive treatment program who received a standard aftercare orientation with 20 graduates who received this intervention plus social reinforcement of aftercare group therapy attendance. The social reinforcement group showed less alcohol use than the standard care group at a 6-month follow-up assessment as measured by the Addiction Severity Index (ASI), but not less drug use.