Hosted by www.Geocities.ws

@ 2008 JLBP All Rights Reserved

 

Diamond Geology Records Bank

Beginning

Diamond Geology Records Bank

South America

Diamond Geology Records Bank

North America

Diamond Geology Records Bank

Africa

Diamond Geology Records Bank

Europe

Diamond Geology Records Bank

India

Diamond Geology Records Bank

China

Diamond Geology Records Bank

Australia

Diamond Geology Records Bank

Others and Notices

Diamond Geology Records Bank

Dr. JLBP

 

--------------------------------------------------------------------------------------------------------------------------------------------

!!Twenty Years from now you will be more disappointed with the things that you didn't do than by the ones you did do.

So throw off the bowlines. Sail away from safe harbour. Catch the trade winds in your sails, Explore, Dream, Discover!!

Mark Twain

--------------------------------------------------------------------------------------------------------------------------------------------

Hosted by www.Geocities.ws

 

 

 

Diamond Geology

Records Bank

Hosted by www.Geocities.ws

 

 

 

Tracing the diamond way for gives world class diamond mines

Jaime Leonardo Baez Presser

Dr. in Geological Sciences

(ICB/UNA - PARAGUAY)

(USP - BRASIL)

[email protected]

 

 

 

 

Mantle xenoliths provide detailed information on the composition of small volumes of subcontinental lithospheric mantle (SCLM) beneath individual volcanic fields; the challenge for the geologist is to extend that information to larger volumes of the lithospheric mantle (Deen et al., 2006 In: GEMOC 12 Years of Research Highlights 2007. http://www.es.mq.edu.au/gemoc/index.html). Until, recently there was no method of mapping the three dimensional structure of cratonic lithosphere (=SCLM), partly because large areas of cratons are covered with thin veneers of Phanerozoic sediments. It is then difficult to use geological observations to map the margins ofcratons (McKenzie & Priestley, in: Lithos 102 (2008)). Seismic tomography provides stunning images that carry information on the structure of the SCLM, and potentially can be used to map the deep interior. Global tomographic studies show that roots with high seismic velocities extend to depths of 150-300 km under Archean cratons, while younger areas typically show thinner roots, with somewhat lower velocities and extend to lesser depths. Seismic tomography is typically interpreted in terms of thermal variations. However, calculations of seismic velocities for mantle-derived xenoliths show that variations in mantle composition can account for as much as 25-percent; of the observed velocity range (Deen et al., 2006 In: GEMOC 12 Years of Research Highlights 2007.).

 

 

Lithospheric thickness variations with the ages (Adapted from a vision gives by Artemieva, I.M., Mooney, W.D., 2001. Thermal thickness and evolution of Precambrian lithosphere: a global study. J. Geophys. Res. 106, 16387 - 16414.). Were the formula z=0.04*t+93.6 (z is lithospheric thermal thickness in km and t is age in Ma)(Artemieva: Global 1 × 1 thermal model TC1 for the continental lithosphere: Implications for lithosphere secular evolution. Tectonophysics 416 (2006) 245 - 277) it could adjust a vision easily on the cratons and belts depth.

 

 

 

 

Locality

Isotope system

Type of Analysis

Inclusion type

Age (Ma)

Age-deep (Km)

Di-Chr-deep

Xen-Chr-deep (Km)

Craton age (Ma)

References

Kalahari

 

 

 

 

 

242

 

 

3700

Diverse published data source

This work

Newlands

(for reference way)

Re-Os

isochron

E-type gnt + cpx

3080-4540

275

 

 

 

Lithos 71 (2003) 323- 336

This work

Kimberley SA

Sm-Nd

model age

P-type gnt

3200 � 100

218-226

 

 

3700

Nature 310, 198-202.

Finsch SA

Sm-Nd

model age

Di-Chr-deep

Xen-Chr-deep

P-type gnt

3200 � 100

3557

218-226

179-236

215

3700

Nature 310, 198-202.

This work

Venetia SA

Sm-Nd

isochron

P-type gnt + cpx Hz

2300 � 40

184-187

206

 

 

16th Annual V.M. Goldschmidt Conference, Melbourne

(Australia), Abstracts.

This work

Jwaneng

 

Di-Chr-deep

Xen-Chr-deep

 

2790-3715

4075*

(*framesite)

 

205-242

257*

223

3700

Diverse published data source

This work

Orapa

 

Di-Chr-deep

Xen-Chr-deep

 

3304

214

204-240

238

2500-3000

Diverse published data source

This work

Premier

 

Di-Chr-deep

 

3159

 

220

 

 

3700

Diverse published data source

This work

Siberia

(Yakutia)

 

 

 

 

230

 

 

3400

Tectonophysics 416 (2006) 245-277

This work

Udachnaya

Re-Os

model age

Di-Chr-deep

P-type sulphides

3502 � 100

3480 � 210

3410

230-238

 

230

 

 

-Geochimica et Cosmochimica Acta 63, 703-711.

-Goldschmidt 2000. Volume 5(2), 776

This work

Aikhal

Re-Os

model ages

P-type sulphides

3274�970

225-263

 

 

 

Goldschmidt 2000. Volume 5(2), 776

Slave

 

 

 

 

255

 

 

4014 (+/-25)

(U-Pb)

http://www.nwtgeoscience.ca

 

Panda CAN

Re-Os

Isochron

Di-Chr-deep

P-type sulphides

3520 �170

3035

228-241

215

 

2680

Contributions to Mineralogy and

Petrology 152, 275-294.

This work

Till, Ekati-Diavick area

 

Xen-Chr-deep

 

2602

201

 

198

2680

http://www.nwtgeoscience.ca

This work

Others.

Rio de la Plata

(Rio Apa Block)

 

 

Xen-Chr-deep

 

3998

 

194-199

202-214

 

254

(~600 chromites from W of Concepcion Dpto.- Paraguay)

2510-2640+

2700-3000++

Sm-Nd

model age+

U-Pb++

in xenocrystal/alluvial zircon

 

Cordani et al. (2003),Terra Nova, v.15 (5): p. 343-349. GONDWANA12

Cordani et al. (2008), 33rd IGC ..

Babinski et al. (2008) , 33rd IGC .

http://ar.geocities.com/jaimeleonardobp/Paraguay.htm

This work

 

Alto Terere Belt

(N, Rio Apa Block)

 

 

 

 

 

182

 

 

1950-2200

Sm-Nd

model age

Cordani et al. (2003),Terra Nova, v.15 (5): p. 343-349. GONDWANA12

Cordani et al. (2008), 33rd IGC.

This work

Suite Amoguija

(W-NW, Rio Apa Block)

 

 

 

 

 

 

167

 

 

1830

U-Pb

2800

Sm-Nd

model age

Cordani et al. (2003),Terra Nova, v.15 (5): p. 343-349. GONDWANA12

Cordani et al. (2008), 33rd IGC.

This work

Acahay Valley

(Rio Tebicuary Proterozoic block in the South of Rio Apa Block)

 

Xen-Chr-deep

 

2137

175

 

 

179

550 (K/Ar)

2038 (U/Pb)

#Presser (1998)

Cordani et al. (2001). III SSAGI, 2001, Pucon - Chile. III Simposio

Sudamericano de Geologia Isotopica, 2001. And references here.

This work

 

No seismic estimation of the some cratons keel(subcontinental lithospheric mantle =SCLM). To estimate the cratons keel (SCLM) were used barometric data obtained from: diamond inclusion chromites, and/or kimberlitic xenocrystal chromites (Pkar=Cr/(Cr+Al)*Cr2O3 (#PRESSER, J.L.B. (1998). Feicoes Mineralogicas de rochas lamprofiricas Mesozoicas da Provincia Alcalina Central, Paraguai Oriental. Sao Paulo, 355p. Tese de Doutoramento, IG-USP. (in Portuguese)), in one way. In other way, if one knows the diamond inclusion ages (isochron/model ages) and/or craton ages (shield-dates) we employed Artemieva formula (z=0.04*t+93.6 (where z is lithospheric thermal thickness in km and t is age in Ma)) (Km= 3.846*Kbar) to calculate z. If are no well know the craton keel age, t was also deduced from the Artemieva formula employing available diamond inclusion chromites and/or kimberlitic xenocrystal chromites pressure formation.
Hosted by www.Geocities.ws

 

 

Mantle structure beneath Kalahari craton in a view of seismic vertical cross sections for P-wave velocity perturbation models determined by inversion of delay times after correction for elevation and crustal thickness (James et al, 2001. Tectospheric structure beneath southern Africa. Geophysical Research Letters, 28, 2485-2488.) and modified (craton deep and included here diamond type and ages) by Shirey (2004. Archean Subduction and Craton Creation:Evidence from Diamonds and Diamondiferous Eclogite). The strong positive velocity perturbations across the region suggest that the seismically-defined keel extends to depths of ~250 to 300km beneath the Kaapvaal craton, and perhaps slightly less (~225 to 250km) beneath the Limpopo mobile belt and Zimbabwe craton (Fouch et al. 2004. SOUTH AFRICAN JOURNAL OF GEOLOGY, 2004, VOLUME 107, PAGE 33 - 44). For this time the Kalahari craton seismic structure is considerate as the best study craton in relation to seismic information and so view as key to understand others large world cratons. Craton areas that in some case are covered with thin veneers sediments.

 

 

Kalahari craton estimated deep, in a view of Jame�s seismic P-wave data at a depth of 300km, using barometric data from diamond inclusions (white-color); xeno-crystals found in diamond-bearing kimberlites (brown-color) and diamond inclusions ages-data (red-color). Consequently, if the Kalahari peridotitic craton root is approximately 257 kilometers�. =257Km-93.6/0.04 =4.085 Ma, the Kalahari craton formation would have been happened in the Hadean?. The numbers indicate depth in kilometers.

 

 

Detail of the Rio Apa cratonic-block estimated deep, in a view of Rocha (2008. Tomografia sismica com ondas P e S para o estudo do manto superior no Brasil, PHD thesis, IAG, University of Sao Paulo, Sao Paulo (in Portuguese)) seismic P-wave data at a depth of 300km, using barometric data from kimberlitic and alluvial chromites xeno-crystal (brown-color) and some shield published ages-data. The Rio Apa peridotitic cratonic-block root is approximately 253.5 kilometers�.....253.5 Km-93.6/0.04 =3.998 Ma, the Rio Apa cratonic-block formation would have been also happened in the Hadean like the Kalahari craton?. The numbers indicate depth in kilometers.

 

 

ciencias-de-la-tierra
contador gratis

GeoCities va a cerrar el 26 de octubre del 2009. Si quieres guardar los archivos y las imagenes del sitio, descargalos ya. Si deseas obtener instrucciones y mas informacion, visita el centro de asistencia. Una vez que tengas tus paginas e imagenes guardadas en tu equipo, podras volver a crear tu sitio con cualquier proveedor de alojamiento que desees, como por ejemplo STRATO. Para encontrar una forma nueva de conectarte en linea, configura tu perfil de Yahoo, con lo que te resultara mas facil conectarte y compartir informacion con otras personas que te importan. Ver detalles.

1