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Dear Colleagues,
 I have gotten a rock showing the assemblage An98 +Cpx (>10 wt% Al2O3) + garnet (Grs58-65Alm32-33Pry8-10) + Spinel (XMg= 0.2-0.4) + amphibole (Magnesiohastingsite) with minor titanite and zoisite. The rock occurs as a raft (100 X 3 sq feet) within felsic orthogneiss. The rock shows cm-dm thick compositional layers rich in plagioclase and mafic phases. My first impression is the rock could be a fragment of a troctolite dyke that was metamorphosed to spinel-grarnet-CPx bearing assemblage. I solicit your valuable opinion on this. I shall be thankful to have some references that publish high aluminous clinopyroxene in metamorphic rock.
Thanking you in advance,
Cheers,
Pulak

N.B. I append a field photograph.


On Fri, Aug 2, 2013 at 4:02 PM, Michael Brown <[log in to unmask]> wrote:
Abstract deadline - next Tuesday, Aug 6

Topical Session T258, GSA Meetings Oct 27-30, 2013

Title: The Pulse of the Earth:  Episodic and Periodic Events on Timescales of ≥ 10 million years

Co-chairs:  Kent Condie, Michael Brown, Stephen Meyers

It has been over 60 years since the publication of Umgrove's "The Pulse of the Earth".  The 125th Anniversary of the GSA seems an appropriate time to recognize this book as well as the numerous papers published later related to episodic and periodic events in Earth history.  This session will address possible common links between terrestrial, oceanic, atmospheric and biologic events, and connections between surficial and deep earth processes including the supercontinent cycle.  Papers on any aspect of the theme are welcome, including isotopic dating methods and problems related to resolution and interpretation of episodic and periodic geologic events.

Invited speakers are: Nick Arndt (Université Joseph Fourier, Grenoble, France), Craig O'Neill (GEMOC Macquarie University, Sydney, Australia), Bjarte Hannisdal (University of Bergen, Bergen, Norway)

Abstract deadline is August 6, see: http://community.geosociety.org/2013AnnualMeeting/Sessions/Abstracts

We hope you will submit an abstract for our session.

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__________________________________________________________

Michael Brown, Professor of Geology

Department of Geology
Geology Building (#237)
University of Maryland
College Park
MD 20742-4211
USA
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http: www.geol.umd.edu
Dept. office: 301 405 4082; Direct line: 301 405 4080
Direct fax: 301 314 7970; Dept. fax: 301 314 9661

LABORATORY FOR CRUSTAL PETROLOGY (Information at:
http: www.geol.umd.edu/pages/faculty/BROWN/LCP/lcp.htm)
__________________________________________________________