Neoproterozoic ‘anomalous’ kimberlites of Guaniamo, Venezuela: Mica kimberlites of ‘isotopic transitional’ type

Manganilmenite in the Magnetite Ore Body from Pokphur Area of Nagaland, North East India and the Possibility of Microdiamonds in the Ophiolites of Indo-Myanmar Ranges

“…Inclusions of lowMg, Mn-ilmenite were found in placer diamonds from Guaniamo, Venezuela [24][25][26] . Also, the manganilmenites found in tills across Lena West both in and outside the Cretaceous basin are similar to those in the kimberlites from Guanaimo 27 . Recently manganilmenite has been found as an inclusion in a diamond from a primary deposit kimberlitic pipe-Pandrea-7 in the Juina area of Brazil 13 .…”

Layered mantle structure beneath the western Guyana Shield, Venezuela: Evidence from diamonds and xenocrysts in Guaniamo kimberlites

“…Both lherzolite and harzburgite garnets have been analysed from each of the two kimberlite occurrences; La Ceniza (''The Ash'') and Desengano (''Disappointment''). There are differences in major element Schulze et al (2003a), Kaminsky et al (2004), this paper, and the unpublished database of the Guaniamo Mining Company. Diamond inclusion data from Nixon et al (1994) and Kaminsky et al (2000).…”

“…The single clinopyroxene geothermobarometer of Nimis and Taylor (2000) has been applied to Cr-diopside xenocrysts recovered from fresh Guaniamo kimberlite drill core, to determine the thermal regime (paleo-geothermal gradient) in the mantle at the time of kimberlite eruption (approximately 712 Ma ago-see Kaminsky et al, 2004). The partitioning of Ni between garnet and olivine is temperature dependent (Griffin et al, 1989), and we have applied the Ni-in-garnet thermometer of Canil (1999) to our new garnet xenocryst data, and those published for Cr-pyrope inclusions in Guaniamo diamonds.…”

“…Five Guaniamo Cr-diopsides (three single cpx grains from Kaminsky et al (2004), one each from the Cr-diopside/olivine pair and the garnet peridotite in Table 3) meet the criteria of Nimis and Taylor (2000) for using their single crystal Cr-diopside thermobarometer to calculate pressure (P) and temperature (T) conditions of equilibration. Calculated equilibration conditions are in the range 890-1040°C and 38-45 kbar (Table 6).…”

Mineralogy and Geochemistry of Kimberlites Nk-2 and Kk-6, Narayanpet Kimberlite Field, Eastern Dharwar Craton, Southern India: Evidence for a Transitional Kimberlite Signature

“…Kimberlites exhibiting such transitional characteristics are also reported from the Koidu province in West Africa (e.g., Taylor et al 1994), the Arkhangelsk region on the Kola-Kuloi craton (e.g., Beard et al 2000) and Nukyan region, Siberia (e.g., Aghashev et al 2001) in Russia, the São Fransisco craton in Brazil (e.g., Gibson et al 1995), the Kimberley craton in northwestern Australia (e.g., Edwards et al 1992), the Aravalli-Bundelkhand craton in northeastern India (e.g., Chalapathi Rao 2005, Masun et al 2009), the Northwest Territories in Canada (e.g., Dowall et al 2000), and the Guyana craton in Venezuela (Kaminsky et al 2004). Their emplacement ages range from Proterozoic to Mesozoic, thereby implying their global occurrence in space as well as time.…”