March GEOLOGY and GSA TODAY media ...(ws nanometer-scale separation of mangane...)

Date:2/29/2008

ws nanometer-scale separation of manganese- and iron-bearing phases, possibly reflecting differing degrees of chemical oxidation. A suite of late-grown manganese and iron phases commonly occur also, together with sparse barium and strontium sulfates, and rare, entrained, carbonaceous particles. These data demonstrate that varnish remains a mineralogically and structurally active system. They furthermore suggest that there must be strict climate controls on varnish growth.

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Forearc diamond from Japan

Simon Wallis et al., Department of Earth and Planetary Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8602, Japan. Pages 219-222.

Most diamonds are brought to the Earth's surface in explosive volcanic eruptions in geologically old continental regions. Volcanism in convergent margins is generally thought to be too shallow in origin to be a host for diamond. Micro-diamonds found in xenoliths within a lamprophyre dike in southwest Japan show this assumption is incorrect, and, furthermore, that diamonds occur in a wider range of geological settings than previously realized. This may help explain the origin of some known anomalous diamond deposits. Studies of associated minerals show the newly recognized diamond-bearing rocks rose from depths of around 160 km and cooled from temperatures of ~1500 C. This result implies that mantle flow in convergent plate boundaries occurs on a larger scale that previously recognized.

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First exposure ages from the Amundsen Sea Embayment, West Antarctica: The Late Quaternary context for recent thinning of Pine Island, Smith, and Pope Glaciers

Joanne Johnson et al., British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK. Pages 223-226.

Dramatic acceleration and thinning of major ice streams in the Amundsen Sea sector of the West Antarctic Ice Sheet have been observed during the last t
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Contact: Ann Cairns acairns@geosociety.org 303-357-1056 Geological Society of America Source:Eurekalert

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