... the Roraima Group is unknown. A West African source has been suggested by some authors but supporting evidence is lacking. A second source of diamonds in the Guyana Shield is responsible for the diamond-bearing alluvial deposits in the Guaniamo district of western Venezuela. For over a decade the kimberlite...

...Zdenek Johan; Daniel Ohnenstetter Abstract Zincochromite associated with chromite and magnesiochromite was found in heavy-mineral concentrates from the Quebrada Grande placer deposit in the Guaniamo River diamondiferous district, Venezuela. It occurs in subhedral to anhedral grains from 0.1 to 0.7...

... of diamond growth ( Meyer 1982 , Harte & Harris 1994 , Davies et al . 1999 ). Diamond grains from the Guaniamo district contain mineral inclusions of all three suites. Ninety-three inclusions were extracted from 77 grains of diamond, of which ten (13%) are of the peridotitic paragenesis and one...

... province which hosts the highly diamondiferous Guaniamo kimberlites, and the Amazonas province containing the Los Pijiguaos plateau bauxite deposits. FIGURE 1. Geologic provinces of the Amazon craton. Modified after Santos et al. (2000) and Tassinari and Macambira (1999) . FIGURE 2...

...Felix V. Kaminsky; Olga D. Zakharchenko; Galina K. Khachatryan; William L. Griffin; Dominic M. DeR. Channer Abstract A set of 77 diamond crystals from the Los Coquitos placer on the Guaniamo River in Bolivar State, Venezuela, has been comprehensively studied and compared to previously studied...

... = Arenápolis, BA = Baoule, BV = Boa Vista, CA = Canastra, CO = Los Coquitos, CR = Coromandel, DC = Dachine, EK = Ekereku, GU = Guaniamo, JW = Jawalla, KM = Kamarang, KU = Kurupung, KW = Konawaruk, MG = Mano Gadua, MK = Maikwak, MM = Monkey Mt., NA = Nassau, RO = Rosebel, SE = Seguela, TE = Tepequém, TO = Tongo...

... district was published D.C. in 1904 when to assess the Jackling proposal for a in 1912 and in it he describes the the suggestion was large-scale, low-grade mining operation. complex geometry of the veins and made by Josiah E. Spurr that there was a faults, the wall-rock alteration, and need for a new...

... Area, Sundargarh District, Odisha, India . Current Science , 111 , 1917 – 1921 . Johan Z. and Ohnenstetter D. ( 2010 ) Zincochromite from the Guaniamo river diamondiferous placers, Venezuela: evidence of its metasomatic origin . The Canadian Mineralogist , 48 , 361 – 374...

.... Sobolev , N.V. , E.S. Yefimova , D.M. Channer , P.F.N. Anderson , and K.M. Barron , Unusual upper mantle beneath Guaniamo, Guyana shield, Venezuela: Evidence from diamond inclusions , Geology , 26 , 11 , 971 – 974 , 1998 . 44...

... been mined since the end of the nineteenth century (only the more important districts are indicated in Fig. 15 ), but most of the mining areas are located in modern deposits derived from nearby mature thin quartz-pebble conglomerates of the Arai Formation ( Fig. 3D ) in the lower part of the Roraima...

... is in agreement with the olivine inclusion compositions at other localities with clearly dominating E-type diamonds over U-type diamonds. However, data on diamond inclusion compositions for some similar mines including Jwaneng ( Stachel et al. , 2004 ) and, especially, Guaniamo, Venezuela ( Sobolev et al...

... patterns in low density geochemical maps of the C-horizon of podzols in Arctic Europe?— Clemens Reimann and Victor Melezhik 963 Thermodynamics of a magmatic gas phase 50 years later: Comments on a paper by John Verhoogen (1949)— James Nicholls 1,313 Diamond from the Guaniamo area, Venezuela...

..., kimberlites) among Permo-Tri-assic traps. Neither were diamonds or kimberlites found in the inner Vilyui basin. Only two finds of type 2 diamonds were documented in the vast territory of the Aldan District. Western Yakutia is best studied; it is called the Yakutian diamond province. Nevertheless, despite all...

... of these rocks. Spectra from these occurrences are sufficiently disturbed that they are not further considered here. Weathering, particularly in tropical climates, can impose profound chemical changes on kimberlite. The Guaniamo kimberlite sheets from Venezuela ( Kaminsky et al . 2004 ) show mobility of Y...

... , D. B. 1981 . Occurrence and origin of garnets in the South Mountain Batholith. Nova Scotia . Canadian Mineralogist 19 , 19 – 24 . Auden , J. B. 1933 . Vindhyan sedimentation in the Son Valley, Mirzapur District . Memoir Geological Survey of India 62 , 141 – 250 . Aydar...

... and related heat and mass transport —A. Simakin and A. Ghassemi 411 3 He/ 4 He ratios in well gases in the Kinki district, SW Japan: Surface appearance of slab-derived fluids in a non-volcanic area in Kii Peninsula —Takuya Matsumoto, Tetsuro Kawabata, Jun-ichi Matsuda, Koshi Yamamoto, and Koichi...

... ( Mitchell 1995 ); K4 Buffalo Hills, Canada ( Eccles et al. 2004 ); Porpoise, Lac de Gras, Canada ( Armstrong et al. 2004 ); Guaniamo, Venezuela ( Kaminsky et al. 2004 ) and Adamantin, Quebec, Canada (Barnett and Laroulandie 2017). An Al–Fe–Mg ternary plot is also useful for examining phlogopite mica Al...

... arises in using the IMA nomenclature in classifying Zr-pyrochlore from the Guaniamo kimberlite, Venezuela (Sharygin et al. , 2009 ). However, establishing a Si-dominant group of the pyrochlore supergroup is not feasible as the crystal-chemical role of Si in the pyrochlore structure is debatable...

..., P.J. (1978) On the composition of some Canadian Green Garnets . The Canadian Mineralogist 16 , 205 – 206 . Fanlo, I., Gervilla, F., Colás, V., & Subías, I. (2015) Zn-, Mn- and Co-rich chromian spinels from the Bou-Azzer mining district (Morocco...

..., Scheibengraben and Bienergraben beryl–columbite pegmatites in the Maršíkov District (Silesian Unit, Bohemian Massif, Czech Republic). Textural and compositional variations of microlite-group minerals were examined using electron probe micro-analyses and microRaman spectroscopy (μRS). A complex post-magmatic...