[meteorite-list] Mercury?

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:15 2004
Message-ID: <3B3D9884.DBE53898_at_lehrer1.rz.uni-karlsruhe.de>

Steve wrote:

> Certainly magmatic processes on the planet Murcury would
> have ended at about the same time as they did on the moon
> about 3.9 billion years ago. What is the age date angrites?


Hello Steve, Ed, and List,

LUGMAIR G.W. et al. (1989) Isotopic evolution and age of
Angrite LEW86010 (abs. Meteoritics 24-4, 1989, 296):

The Rb-Sr studies show that the initial 87Sr/86Sr isotope ratios
of all mineral fractions of LEW 86010, Angra dos Reis Px, and
Moore County Pl, calculated for an assumed age of 4.55 Ga,
are indistinguishable within the uncertainties of measurement.

McKAY G. et al. (1995) Exotic olivine in Antarctic
angrites LEW 87051 and Asuka 881371 (Meteoritics
30-5, 1995, A543-A544):

Angrites are basaltic meteorites with very early formation ages
suggesting magmatic activity on their parent body shortly after
accretion.

NYQUIST L.E. et al. (1994) Neodymium, Strontium and Chromium
Isotopic Studies of the LEW 86010 and Angra dos Reis Meteorites
and the Chronology of the Angrite Parent Body (Meteoritics 29-6,
1994, 872-885):

The presence of excess fission Xe from 82 Ma 244Pu, very low initial
87Sr/86Sr ratios, and a Pb-Pb age of ca. 4.55 Ga showed Angra dos Reis
to be one of the most ancient meteorites ... The U-Pb ages, Sm-Nd ages,
and 244Pu fission track ages all confirmed ADOR's antiquity. Although
ancient, ADOR is far from "primitive" in a petrologic and geochemical
sense, however. Instead, it is a unique, igneous, ultramafic pyroxenite
containing about 93% of fassaitic pyroxene ... Conventional Sm-Nd
ages obtained in this investigation ... and Pb-Pb ages ... confirmed
the antiquity of LEW 86010 ... Detection of fossil 53Cr is especially
important since it shows that these igneous rocks were produced within
a few million years of the closure of the Solar System to live 53Mn from
stellar sources.

See also:

LUGMAIR G.W. et al. (1992) Age and isotopic relationships among
the angrites LEW 86010 and Angra dos Reis (GCA 56, 1673-1694).


Best wishes,

Bernd
Received on Sat 30 Jun 2001 05:14:44 AM PDT