FW: RE: [meteorite-list] Ureilites/Venus - Ureilite carbon
From: Joseph Hum <jkarlhum_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:02 2004 Message-ID: <41200195212455590_at_earthlink.net> ------=_NextPart_84815C5ABAF209EF376268C8 Content-type: text/plain; charset=US-ASCII ----- Original Message ----- From: Joseph Hum To: Sent: 9/20/01 8:34:47 PM Subject: FW: RE: [meteorite-list] Ureilites/Venus - Ureilite carbon ----- Original Message ----- From: Joseph Hum To: C.L.Smith_at_open.ac.uk Sent: 9/20/01 8:26:07 PM Subject: RE: [meteorite-list] Ureilites/Venus - Ureilite carbon Howdy, What you say may very well be the case... However, you are saying then, Ureilites, do not possess any features or characteristics of a differentiated body origin?? Insofar as isotopes go, you claimed there is a " mixing " of isotopes occurring and you attempt to explain it away with conventional/usual arguments; why not from a differentiated body?? Moreover, these isotopes of 02,N2,Ar/Ne, Xe, etc. DO come from differentiated bodies... the most important aspect of proving Martian meteorites was due to Martian atmosphere N2 and other isotopes being trapped within minerals in the rocks... So I don't understand what you are talking about... I think we should be analyzing Venusian atmosphere and other data on the Venusian rocks obtained from Vega 1 and 2 and other probes and correlating this data to Ureilites... instead of making armchair judgements out of hand, esp. when you claim there is allot of uncertainty as to the petrogeneisis of Ureilites... maybe you're not looking in the right place To explain this phenomenon... Also, take into account I never said they are purely Venusian rock; I said they are possible Venus and a portion of the IMPACTOR... I read somewhere that the diamonds in Ureilites are different from the ones found in meteorites like Allende; they are larger for one, and did NOT resemble ones created by "shock" as in Canyon Diablo, they are "higher" quality!, like ones produced on a planetary body... and the carbon forms/ratios seemed peculiar compared to other meteorites... At any rate, I really do appreciate you information and it will help me... in my analysis of Ureilites. As I stated before, instead of just relying on theory and supposition to explain these Enigmatic Rocks, I want to correlate Data from Venus and Ureilites to see relationships, if in fact they exist... Which I have and I go in another direction--- toward Venus! Best Regards, Caroline J.K. Hum ----- Original Message ----- From: To: jkarlhum_at_earthlink.net Sent: 9/20/01 8:13:03 AM Subject: RE: [meteorite-list] Ureilites/Venus - Ureilite carbon Hi Joseph Everyone Hopefully I will be able to give some background into ureilite carbon in terms of its abundance, form, isotopes etc. and petrogenetic implications. I think I should start by saying that, along with many other features e.g. O isotopes, noble gases, Sm-Nd ages, ureilite carbon is poorly understood in terms of petrogenesis and there are many differing models that attempt to account for the carbon that we see in the ureilite samples. Ureilite carbon may be divided into four main types or forms; amorphous C, graphite, diamond/lonsdaleite and carbide (iron carbide - cohenite). The vast majority of ureilites contain C in varying amounts usually from about 1 - 5wt% although at least 3 samples contain very little C ( 0.02 wt%) which has been measured using very sensitive analytical techniques at the Open University. A further sample investigated does not reveal any recognisable C in thin section (Goodrich et al. 2001) although this sample has not been investigated at the OU. Interestingly all the very low carbon samples have very similar mg# and mineralogical assemblages. Also two ureilite samples measured contain alot of C (5.9 and 6.9 wt%) which has some interesting implications for ureilite petrogenesis (see later section). In terms of their C isotopic composition the ureilites display a range in d13C between ~ -11? and ~ -1? and the samples appear to split into two groups with a "light" group clustering between -8? and -11? and a "heavy" group clustering between -1? and -3? (Grady et al. 1985). Recent work has suggested that the range in isotopic compositions seen in the ureilites may be be due to a mixing between a 'primary', isotopically light C, derived from a carbonaceous chondrite-like precursor material and isotopically heavier C, i.e. has lost 12C, during reduction processes on the ureilite parent body (UPB) (Smith et al. 2001). The source of ureilite C is poorly understood. The vast majority of authors believe that ureilite C is derived from a carbonaceous chondrite (CC)-like precursor material due to the simple fact that the carbonaceous chondrites are the most similar to the ureilites in terms of C abundance. However, as I mentioned above this hypothesis may be flawed with the discovery that two ureilites contain more C than any known CC group. This is not to sound the death knell though for the link with CC carbon as there may be a concentration mechanism working or there may be a as yet unrecognised CC group lurking in the asteroid belt which has the necessary high C concentration. Of course there are other features that link the ureilites with the CCs including their O isotope compositions and the fact that at least one of the polymict ureilites Nilpena contains clasts that are similar to CI material. Other authors believe that at least some ureilite C (notably amorphous C and diamond) were derived from nebular gases by condensation processes. If we believe that the ureilite C is indeed derived from a CC-like source then the next problem is when the C was actually present in the UPB. Some authors suggest that ureilite C is a primary feature, in that it was certainly present in the juvenile UPB. Evidence for this includes the presence of iron carbide (cohenite) spherules within primary magmatic olivine grains (Goodrich and Berkley, 1986). On the other hand some authors believe that ureilite C is a 'secondary' feature injected into the UPB at a later stage in its history. Evidence for this hypothesis includes the presence of planetary type noble gases (which should not really be preserved in a differentiated body) which may be preserved in an unfractionated state if they were injected in a very rapid shock event. Certainly the ureilites have undergone shock to a greater or lesser extent as can be clearly seen in thin sections. Also, as has been mentioned already on this thread, the ureilite Sm-Nd systematics do show ages of 4.23 and 3.74 Ga. These younger ages may be suggestive of a resetting event which reasonably may be accounted by major disruption of the UPB during a large shock event. One last point with regards to the shock that has clearly affected the ureilites is that it is widely accepted that the origin of the diamond in the ureilites is due to the shock transformation of graphite to diamond. I hope this answers at least some of the questions with regards to ureilite C. I hope that readers can see we do not, by any means, have any definite answers to all the questions that the ureilites pose. Carbon is only one small part of the ureilite problem which is why they are such an interesting (and infuriating) meteorite group to study! In reference to the question as to whether the ureilites may be derived from Venus I think it is EXTREMELY unlikely! They posess too many features (O isotopes, noble gases, siderophile element abundances etc. etc.) that rule out derivation from a planetary sized differentiated body. Regards Caroline Planetary and Space Sciences Research Institute The Open University Walton Hall Milton Keynes Buckinghamshire MK7 6AA Tel : +44 (0)1908 655160 Fax: +44 (0)1908 858022 E-mail: C.L.Smith_at_open.ac.uk Refs: Goodrich, C. A.; Fioretti, A. M.; Tribaudino, M.; Molin, G. (2001) Primary trapped melt inclusions in olivine in the olivine- augite-orthopyroxene ureilite Hughes 009. GCA, 65, no. 4, 621-652. Grady, M. M.; Wright, I. P.; Swart, P. K.; Pillinger, C. T. (1985) The carbon and nitrogen isotopic composition of ureilites: implications for their genesis. GCA, 49, 903-915. Smith, C. L.; Franchi, I. A.; Wright, I. P.; Grady, M. M.; Pillinger, C. T. (2001) Ureilite Graphite: Shocking Implications. MAPS, 36, Suppl. 193. Goodrich, C. A.; Berkley, J. L. (1986) Primary magmatic carbon in ureilites - Evidence from cohenite-bearing metallic spherules. GCA, 50, 681-691. -----Original Message----- From: Joseph Hum [SMTP:jkarlhum_at_earthlink.net ] Sent: 18 September 2001 09:01 To: Meteorite-list_at_meteoritecentral.com Subject: [meteorite-list] Ureilites/Venus Hi, I am working on some lines of thought and I will reply soon. One of the aspects of Ureilites I would like to be elucidated is the amount of diamonds present and other carbon forms that may require a planetary body to produce; moreover, are they similar or different than say Allende, which is a more "primitive" meteorite type?? Best Regards, J.Karl Hum --- Joseph Hum --- jkarlhum_at_earthlink.net mailto:jkarlhum_at_earthlink.net --- EarthLink: It's your Internet. --- Joseph Hum --- jkarlhum_at_earthlink.net --- EarthLink: It's your Internet. --- Joseph Hum --- jkarlhum_at_earthlink.net --- EarthLink: It's your Internet. --- Joseph Hum --- jkarlhum_at_earthlink.net --- EarthLink: It's your Internet. ------=_NextPart_84815C5ABAF209EF376268C8 Content-Type: text/html; charset=US-ASCII <HTML><HEAD> <META content="text/html; charset=windows-1251" http-equiv=Content-Type> <META content="MSHTML 5.00.3211.1700" name=GENERATOR></HEAD> <BODY> <DIV> </DIV> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A href="mailto:jkarlhum_at_earthlink.net" title=jkarlhum@earthlink.net>Joseph Hum</A> </DIV> <DIV style="FONT: 10pt arial"><B>To: </B></DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> 9/20/01 8:34:47 PM </DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> FW: RE: [meteorite-list] Ureilites/Venus - Ureilite carbon</DIV> <DIV><BR></DIV><FONT size=2> <DIV> </DIV> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A href="mailto:jkarlhum_at_earthlink.net" title=jkarlhum@earthlink.net>Joseph Hum</A> </DIV> <DIV style="FONT: 10pt arial"><B>To: </B><A href="mailto:jkarlhum_at_earthlink.net" title=jkarlhum@earthlink.net>C.L.Smith@open.ac.uk</A></DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> 9/20/01 8:26:07 PM </DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> RE: [meteorite-list] Ureilites/Venus - Ureilite carbon</DIV> <DIV><BR></DIV><FONT size=2> <DIV>Howdy,</DIV> <DIV> </DIV> <DIV>What you say may very well be the case... However, you are saying then, Ureilites, do not possess</DIV> <DIV>any features or characteristics of a differentiated body origin?? Insofar as isotopes go, you claimed</DIV> <DIV>there is a " mixing " of isotopes occurring and you attempt to explain it away with conventional/usual</DIV> <DIV>arguments; why not from a differentiated body?? Moreover, these isotopes of 02,N2,Ar/Ne, Xe, etc.</DIV> <DIV>DO come from differentiated bodies... the most important aspect of proving Martian meteorites was</DIV> <DIV>due to Martian atmosphere N2 and other isotopes being trapped within minerals in the rocks... So I don't</DIV> <DIV>understand what you are talking about... I think we should be analyzing Venusian atmosphere and</DIV> <DIV>other data on the Venusian rocks obtained from Vega 1 and 2 and other probes and correlating this</DIV> <DIV>data to Ureilites... instead of making armchair judgements out of hand, esp. when you claim there is</DIV> <DIV>allot of uncertainty as to the petrogeneisis of Ureilites... maybe you're not looking in the right place To</DIV> <DIV>explain this phenomenon... Also, take into account I never said they are purely Venusian rock; I said</DIV> <DIV>they are possible Venus and a portion of the IMPACTOR... I read somewhere that the diamonds in</DIV> <DIV>Ureilites are different from the ones found in meteorites like Allende; they are larger for one, and did NOT</DIV> <DIV>resemble ones created by "shock" as in Canyon Diablo, they are "higher" quality!, like ones produced</DIV> <DIV>on a planetary body... and the carbon forms/ratios seemed peculiar compared to other meteorites...</DIV> <DIV>At any rate, I really do appreciate you information and it will help me... in my analysis of Ureilites.</DIV> <DIV>As I stated before, instead of just relying on theory and supposition to explain these Enigmatic Rocks,</DIV> <DIV>I want to correlate Data from Venus and Ureilites to see relationships, if in fact they exist... Which I have</DIV> <DIV>and I go in another direction--- toward Venus!</DIV> <DIV> </DIV> <DIV> </DIV> <DIV>Best Regards,</DIV> <DIV>Caroline</DIV> <DIV> </DIV> <DIV>J.K. Hum </DIV> <DIV> </DIV> <DIV> </DIV> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A href="mailto:C.L.Smith_at_open.ac.uk" title=C.L.Smith@open.ac.uk></A></DIV> <DIV style="FONT: 10pt arial"><B>To: </B><A href="mailto:C.L.Smith_at_open.ac.uk" title=C.L.Smith@open.ac.uk>jkarlhum@earthlink.net</A></DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> 9/20/01 8:13:03 AM </DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> RE: [meteorite-list] Ureilites/Venus - Ureilite carbon</DIV> <DIV><BR></DIV><FONT size=2> <P> <DIV>Hi Joseph & Everyone</DIV> <DIV> </DIV> <DIV>Hopefully I will be able to give some background into ureilite carbon in</DIV> <DIV>terms of its abundance, form, isotopes etc. and petrogenetic implications.</DIV> <DIV> </DIV> <DIV>I think I should start by saying that, along with many other features e.g. O</DIV> <DIV>isotopes, noble gases, Sm-Nd ages, ureilite carbon is poorly understood in</DIV> <DIV>terms of petrogenesis and there are many differing models that attempt to</DIV> <DIV>account for the carbon that we see in the ureilite samples.</DIV> <DIV> </DIV> <DIV>Ureilite carbon may be divided into four main types or forms; amorphous C,</DIV> <DIV>graphite, diamond/lonsdaleite and carbide (iron carbide - cohenite). The</DIV> <DIV>vast majority of ureilites contain C in varying amounts usually from about 1</DIV> <DIV>- 5wt% although at least 3 samples contain very little C (<0.02 wt%) which</DIV> <DIV>has been measured using very sensitive analytical techniques at the Open</DIV> <DIV>University. A further sample investigated does not reveal any recognisable C</DIV> <DIV>in thin section (Goodrich et al. 2001) although this sample has not been</DIV> <DIV>investigated at the OU. Interestingly all the very low carbon samples have</DIV> <DIV>very similar mg# and mineralogical assemblages. Also two ureilite samples</DIV> <DIV>measured contain alot of C (5.9 and 6.9 wt%) which has some interesting</DIV> <DIV>implications for ureilite petrogenesis (see later section).</DIV> <DIV> </DIV> <DIV>In terms of their C isotopic composition the ureilites display a range in</DIV> <DIV>d13C between ~ -11? and ~ -1? and the samples appear to split into two</DIV> <DIV>groups with a "light" group clustering between -8? and -11? and a "heavy"</DIV> <DIV>group clustering between -1? and -3? (Grady et al. 1985). Recent work has</DIV> <DIV>suggested that the range in isotopic compositions seen in the ureilites may</DIV> <DIV>be be due to a mixing between a 'primary', isotopically light C, derived</DIV> <DIV>from a carbonaceous chondrite-like precursor material and isotopically</DIV> <DIV>heavier C, i.e. has lost 12C, during reduction processes on the ureilite</DIV> <DIV>parent body (UPB) (Smith et al. 2001).</DIV> <DIV> </DIV> <DIV>The source of ureilite C is poorly understood. The vast majority of authors</DIV> <DIV>believe that ureilite C is derived from a carbonaceous chondrite (CC)-like</DIV> <DIV>precursor material due to the simple fact that the carbonaceous chondrites</DIV> <DIV>are the most similar to the ureilites in terms of C abundance. However, as I</DIV> <DIV>mentioned above this hypothesis may be flawed with the discovery that two</DIV> <DIV>ureilites contain more C than any known CC group. This is not to sound the</DIV> <DIV>death knell though for the link with CC carbon as there may be a</DIV> <DIV>concentration mechanism working or there may be a as yet unrecognised CC</DIV> <DIV>group lurking in the asteroid belt which has the necessary high C</DIV> <DIV>concentration. Of course there are other features that link the ureilites</DIV> <DIV>with the CCs including their O isotope compositions and the fact that at</DIV> <DIV>least one of the polymict ureilites Nilpena contains clasts that are similar</DIV> <DIV>to CI material.</DIV> <DIV>Other authors believe that at least some ureilite C (notably amorphous C and</DIV> <DIV>diamond) were derived from nebular gases by condensation processes. </DIV> <DIV> </DIV> <DIV>If we believe that the ureilite C is indeed derived from a CC-like source</DIV> <DIV>then the next problem is when the C was actually present in the UPB. Some</DIV> <DIV>authors suggest that ureilite C is a primary feature, in that it was</DIV> <DIV>certainly present in the juvenile UPB. Evidence for this includes the</DIV> <DIV>presence of iron carbide (cohenite) spherules within primary magmatic</DIV> <DIV>olivine grains (Goodrich and Berkley, 1986). On the other hand some authors</DIV> <DIV>believe that ureilite C is a 'secondary' feature injected into the UPB at a</DIV> <DIV>later stage in its history. Evidence for this hypothesis includes the</DIV> <DIV>presence of planetary type noble gases (which should not really be preserved</DIV> <DIV>in a differentiated body) which may be preserved in an unfractionated state</DIV> <DIV>if they were injected in a very rapid shock event. Certainly the ureilites</DIV> <DIV>have undergone shock to a greater or lesser extent as can be clearly seen in</DIV> <DIV>thin sections. Also, as has been mentioned already on this thread, the</DIV> <DIV>ureilite Sm-Nd systematics do show ages of 4.23 and 3.74 Ga. These younger</DIV> <DIV>ages may be suggestive of a resetting event which reasonably may be</DIV> <DIV>accounted by major disruption of the UPB during a large shock event. One</DIV> <DIV>last point with regards to the shock that has clearly affected the ureilites</DIV> <DIV>is that it is widely accepted that the origin of the diamond in the</DIV> <DIV>ureilites is due to the shock transformation of graphite to diamond. </DIV> <DIV> </DIV> <DIV>I hope this answers at least some of the questions with regards to ureilite</DIV> <DIV>C. I hope that readers can see we do not, by any means, have any definite</DIV> <DIV>answers to all the questions that the ureilites pose. Carbon is only one</DIV> <DIV>small part of the ureilite problem which is why they are such an interesting</DIV> <DIV>(and infuriating) meteorite group to study!</DIV> <DIV> </DIV> <DIV>In reference to the question as to whether the ureilites may be derived from</DIV> <DIV>Venus I think it is EXTREMELY unlikely! They posess too many features (O</DIV> <DIV>isotopes, noble gases, siderophile element abundances etc. etc.) that rule</DIV> <DIV>out derivation from a planetary sized differentiated body.</DIV> <DIV> </DIV> <DIV>Regards</DIV> <DIV> </DIV> <DIV>Caroline</DIV> <DIV> </DIV> <DIV>Planetary and Space Sciences Research Institute</DIV> <DIV>The Open University</DIV> <DIV>Walton Hall</DIV> <DIV>Milton Keynes</DIV> <DIV>Buckinghamshire</DIV> <DIV>MK7 6AA</DIV> <DIV> </DIV> <DIV>Tel : +44 (0)1908 655160</DIV> <DIV>Fax: +44 (0)1908 858022</DIV> <DIV> </DIV> <DIV>E-mail: C.L.Smith_at_open.ac.uk</DIV> <DIV> </DIV> <DIV>Refs: Goodrich, C. A.; Fioretti, A. M.; Tribaudino, M.; Molin, G. (2001)</DIV> <DIV>Primary trapped melt inclusions in olivine in the olivine-</DIV> <DIV>augite-orthopyroxene ureilite Hughes 009. GCA, 65, no. 4, 621-652.</DIV> <DIV>Grady, M. M.; Wright, I. P.; Swart, P. K.; Pillinger, C. T.</DIV> <DIV>(1985) The carbon and nitrogen isotopic composition of</DIV> <DIV>ureilites: implications for their genesis. GCA, 49, 903-915.</DIV> <DIV>Smith, C. L.; Franchi, I. A.; Wright, I. P.; Grady, M. M.;</DIV> <DIV>Pillinger, C. T. (2001) Ureilite Graphite: Shocking Implications.</DIV> <DIV>MAPS, 36, Suppl. 193.</DIV> <DIV>Goodrich, C. A.; Berkley, J. L. (1986) Primary magmatic</DIV> <DIV>carbon in ureilites - Evidence from cohenite-bearing metallic</DIV> <DIV>spherules. GCA, 50, 681-691. </DIV> <DIV> </DIV> <DIV> </DIV> <DIV>> -----Original Message-----</DIV> <DIV>> From: Joseph Hum [<A href="mailto:SMTP:jkarlhum_at_earthlink.net">SMTP:jkarlhum@earthlink.net</A>]</DIV> <DIV>> Sent: 18 September 2001 09:01</DIV> <DIV>> <A href="mailto:To:	Meteorite-list_at_meteoritecentral.com">To: Meteorite-list@meteoritecentral.com</A></DIV> <DIV>> Subject: [meteorite-list] Ureilites/Venus</DIV> <DIV>> </DIV> <DIV>> Hi,</DIV> <DIV>> </DIV> <DIV>> I am working on some lines of thought and I will reply soon.</DIV> <DIV>> One of the aspects of Ureilites I would like to be elucidated</DIV> <DIV>> is the amount of diamonds present and other carbon forms</DIV> <DIV>> that may require a planetary body to produce; moreover, are</DIV> <DIV>> they similar or different than say Allende, which is a more "primitive"</DIV> <DIV>> meteorite type?? </DIV> <DIV>> </DIV> <DIV>> Best Regards,</DIV> <DIV>> J.Karl Hum</DIV> <DIV>> </DIV> <DIV>> --- Joseph Hum</DIV> <DIV>> --- <A href="mailto:jkarlhum_at_earthlink.net">jkarlhum@earthlink.net</A> <<A href="mailto:mailto:jkarlhum@earthlink.net">mailto:jkarlhum@earthlink.net</A>></DIV> <DIV>> --- EarthLink: It's your Internet.</DIV> <DIV>> </DIV> <DIV> </DIV> <P></P></FONT> <P></P></BLOCKQUOTE> <DIV> </DIV> <DIV>--- Joseph Hum</DIV> <DIV>--- <A href="mailto:jkarlhum_at_earthlink.net">jkarlhum@earthlink.net</A></DIV> <DIV>--- EarthLink: It's your Internet.</DIV> <DIV> </DIV></FONT> <P></P></BLOCKQUOTE> <DIV> </DIV> <DIV>--- Joseph Hum</DIV> <DIV>--- <A href="mailto:jkarlhum_at_earthlink.net">jkarlhum@earthlink.net</A></DIV> <DIV>--- EarthLink: It's your Internet.</DIV> <DIV> </DIV></FONT> <P></P></BLOCKQUOTE> <DIV> </DIV> <DIV>--- Joseph Hum</DIV> <DIV>--- <A href="mailto:jkarlhum_at_earthlink.net">jkarlhum@earthlink.net</A></DIV> <DIV>--- EarthLink: It's your Internet.</DIV> <DIV> </DIV></BODY></HTML> ------=_NextPart_84815C5ABAF209EF376268C8-- Received on Thu 20 Sep 2001 10:45:05 PM PDT |
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