[meteorite-list] Matrix darkening
From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:10:10 2004 Message-ID: <DIIE.000000390000071F_at_paulinet.de> This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------_=_NextPart_000_0000071F.3EA46CAD Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7Bit Bob inquired: Can someone explain what happens physically or chemically inside a meteorite to turn a light matrix black during the shock (impact) event? Elton responded: Occasionally the shock is so strong that some of the olivine does a phase shift in crystal form to a spinel structure. This high pressure form of olivine is a mineral called Ringwoodite. These veins, in thin translucent section, tend to have a subtle purple tint. Otherwise it looks black and opaque in cross section. Hello Bob, Elton, and List, The high pressure that Elton mentions comes from shock waves in excess of 50 GPa. This causes the transition from olivine to spinel. Lingemann et al. also state that ringwoodite crystallizes most probably not during the short peak pressure pulse but rather during the more extended phase of pressure release. With regard to the "purple tint", the authors state: "The color of the ringwoodite aggregates ranges from purple to blue and colorless." Reference: LINGEMANN C.M. et al. (1994) Ringwoodite in shocked chondrites (abs. Meteoritics 29, 491-492). Best regards, Bernd ------_=_NextPart_000_0000071F.3EA46CAD Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=3DContent-Type content=3D"text/html; charset=3Dwindows-1252"> <META content=3D"MSHTML 6.00.2800.1106" name=3DGENERATOR></HEAD> <BODY style=3D"FONT: 10pt Courier New; COLOR: #000000" leftMargin=3D5 topMargin=3D5> <DIV>Bob inquired:</DIV> <DIV> </DIV> <DIV>Can someone explain what happens physically or <BR>chemically inside a meteorite to turn a light</DIV> <DIV>matrix black during the shock (impact) event?<BR></DIV> <DIV> </DIV> <DIV>Elton responded:</DIV> <DIV> </DIV> <DIV>Occasionally the shock is so strong that some of the olivine does a <BR>phase shift in crystal form to a spinel structure. This high pressure <BR>form of olivine is a mineral called Ringwoodite. These veins, in thin <BR>translucent section, tend to have a subtle purple tint. Otherwise it <BR>looks black and opaque in cross section.</DIV> <DIV> </DIV> <DIV>Hello Bob, Elton, and List,</DIV> <DIV> </DIV> <DIV>The high pressure that Elton mentions comes from shock waves in excess</DIV> <DIV>of 50 GPa. This causes the transition from olivine to spinel. Lingemann</DIV> <DIV>et al. also state that ringwoodite crystallizes most probably not during</DIV> <DIV>the short peak pressure pulse but rather during the more extended phase</DIV> <DIV>of pressure release.</DIV> <DIV> <P>With regard to the "purple tint", the authors state:</P> <P>"The color of the ringwoodite aggregates ranges from purple to blue and colorless."</P> <P>Reference:</P> <P><FONT face=3D"Times New Roman">LINGEMANN C.M. et al. (1994) Ringwoodite in shocked </FONT><FONT face=3D"Times New Roman">chondrites (abs. Meteoritics 29, 491-492).</FONT></P> <P>Best regards,</P> <P>Bernd</P> <P> </P></DIV></BODY></HTML> ------_=_NextPart_000_0000071F.3EA46CAD-- Received on Mon 21 Apr 2003 04:11:58 PM PDT |
 StumbleUpon del.icio.us reddit Yahoo MyWeb
|