scholarly journals Kimberlite indicator minerals and “laterite”, Canadian arctic

2019 ◽  
Keyword(s):  
Canadian Arctic ◽  
Kimberlite Indicator Minerals ◽  
Indicator Minerals

Ultrabasic eruptives with alnöitic-kimberlitic affinities from Malaita, Solomon Islands

1965 ◽  
Vol 34 (268) ◽  
pp. 16-34 ◽  
Author(s):  
J. B. Allen ◽  
T. Deans
Keyword(s):  
Solomon Islands ◽  
Chemical Analyses ◽  
Alkaline Rocks ◽  
Kimberlite Indicator Minerals ◽  
Host Rocks ◽  
Indicator Minerals

SummaryA detrital assemblage of magnesian ilmenite, pyrope, chrome-diopside, rutile, and zircon has been traced to outcropping ultrabasic alkaline rocks, hitherto unknown in the Melanesian region. Analyses and descriptions of these ‘kimberlite indicator minerals’ are given. The host rocks comprise alnöite, an alnöite breccia with calcite matrix, and a magnesian ankaratrite, which are described, with chemical analyses. Emphasis is laid on the abundance of ultrabasic inclusions and xenocrysts and the replacements and transformations they have undergone. Malaita Island promises to contribute significantly to the understanding of the relations between alnöite, melilite basalts, and kimberlites.

scholarly journals The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland

2006 ◽  
Vol 10 ◽  
pp. 41-44 ◽  
Author(s):  
Agnete Steenfelt ◽  
Julie A. Hollis ◽  
Karsten Secher
Keyword(s):  
Lithospheric Mantle ◽  
Chemical Elements ◽  
Country Rock ◽  
Alkaline Rock ◽  
Geological Mapping ◽  
Carbonatite Complex ◽  
West Greenland ◽  
Alkaline Rocks ◽  
Kimberlite Indicator Minerals ◽  
Indicator Minerals

Ultrabasic alkaline magmatic rocks are products of melts generated deep within or at the base of the lithospheric mantle. The magmas may reach the surface to form lavas and pyroclastic deposits; alternatively they crystallise at depth to form dykes or central complexes. The rocks are chemically distinct and may contain high concentrations of economically interesting minerals and chemical elements, such as diamonds, niobium, tantalum, rare earth elements, phosphorus, iron, uranium, thorium, and zirconium. Ultrabasic alkaline rocks are known from several provinces in Greenland, but extrusive facies have only been preserved at a few places; e.g. at Qassiarsuk in South Greenland where pyroclastic rocks occur, and in the Maniitsoq region, where a small volcanic breccia (‘Fossilik’) contains fragments of Palaeozoic limestone. Ultramafic lamprophyre and kimberlite are mainly emplaced as dykes, whereas carbonatite forms large intrusive bodies as well as dykes. The ultrabasic alkaline magmas that have been emplaced at certain times during the geological evolution of Greenland can be related to major episodes of continental break-up (Larsen & Rex 1992). The oldest are Archaean and the youngest dated so far are Palaeogene. Figure 1 shows the distribution of known ultrabasic alkaline rocks in West Greenland. The large and well-exposed bodies of alkaline rocks and carbonatites in the Gardar Province were discovered already in the early 1800s (Ussing 1912), while less conspicuous bodies were discovered much later during geological mapping and mineral exploration. Many alkaline rock bodies, particularly dykes, are difficult to identify in the field because they weather more extensively than the country rock gneisses and form vegetated depressions in the landscape. However, their distinct chemistry and mineralogy render alkaline rocks identifiable in geochemical and geophysical survey data. Thus, the Sarfartôq carbonatite complex was discovered during regional airborne gamma-spectrometric surveying owing to its elevated uranium and thorium contents (Secher 1986). The use of kimberlite indicator minerals has led to the discovery of alkaline rocks such as kimberlites and ultramafic lamprophyres that carry fragments of deep lithospheric mantle. Such rocks may also contain diamonds. Kimberlite indicator minerals are high-pressure varieties of minerals, such as garnet, clinopyroxene, chromite and ilmenite that were formed in the lithospheric mantle. Exploration companies have processed thousands of till samples from southern West Greenland for kimberlite indicator minerals and found many new dykes.

About kimberlite indicator minerals in the Triassic tuffs of the Tunguska sineclise

2010 ◽  
Vol 435 (2) ◽  
pp. 1555-1559
Author(s):  
V. P. Afanasiev ◽  
N. S. Tychkov ◽  
N. P. Pokhilenko ◽  
Yu. I. Ovchinnikov
Keyword(s):  
Kimberlite Indicator Minerals ◽  
Indicator Minerals

scholarly journals Kimberlite indicator minerals in glacial deposits, Lac de Gras area, N.W.T.

1996 ◽  
Author(s):  
B C Ward ◽  
L A Dredge ◽  
D E Kerr ◽  
I M Kjarsgaard
Keyword(s):  
Glacial Deposits ◽  
Kimberlite Indicator Minerals ◽  
Indicator Minerals

scholarly journals The new Massadou diamondiferous kimberlite field in Guinea

2019 ◽  
Vol 61 (4) ◽  
pp. 92-100
Author(s):  
V. P. Afanasiev ◽  
E. I. Nikolenko ◽  
N. V. Glushkova ◽  
I. D. Zolnikov
Keyword(s):  
Satellite Images ◽  
Weathering Profile ◽  
Kimberlite Indicator Minerals ◽  
Indicator Minerals ◽  
Wide Zone ◽  
Kimberlite Field ◽  
Diamondiferous Kimberlite

A new kimberlite field, called Massadou, has been discovered in southeastern Guinea near Macenta city. The field consists of numerous ~1 m thick kimberlite dikes with low diamond contents; altogether 16 dikes have been found so far. Mineralization occurs along a 600 m wide zone distinct in satellite images, which is oriented in the same way as the K4 kimberlite reported by Huggerty. The Massadou kimberlite is covered by a thick laterite weathering profile. Main kimberlite indicator minerals found in the area are pyrope, chromite, and ilmenite. The latter occurs as zoned grains with a high-Fe core (hemoilmenite) surrounded by a parallel-columnar aggregate in the rim. The aggregate has a composition of ordinary kimberlitic Mg ilmenite and results from interaction of hemoilmenite with the kimberlite melt. The kimberlite age is estimated as 140—145 Ma by analogy with the surrounding fields. The dikes independent products of kimberlite magmatism in the Guinea-Liberia shield rather than being roots of pipes as interpreted by Skinner (2004). Therefore, the erosion cutout is moderate, and there are no reasons to expect the presence of large and rich diamond placers.

scholarly journals Chemical studies of kimberlite indicator minerals from stream sediment and till samples in the southern Mackenzie region (NTS 85B, C, F, G), Northwest Territories, Canada

2021 ◽  
Author(s):  
I R Smith ◽  
S J A Day ◽  
R C Paulen ◽  
D G Pearson
Keyword(s):  
Rare Earth ◽  
Northwest Territories ◽  
Stream Sediment ◽  
Chemical Analyses ◽  
Great Slave Lake ◽  
Chemical Studies ◽  
Kimberlite Indicator Minerals ◽  
Indicator Mineral ◽  
Indicator Minerals ◽  
Field Area

Till (n=196) and stream sediment (n=60) samples were collected in the area south and west of Great Slave Lake, Northwest Territories (NTS 85B, C, F, and G), over the course of 3 summer field seasons. Samples were processed to recover kimberlite and other indicator minerals. This report summarizes results of the kimberlite indicator mineral (KIM) studies, including measures of KIM mineral types, abundances, and chemistry (major, trace, and rare earth elements). KIMs were present in 24% of the samples collected, and only 183 KIM grains in total were recovered, of which Cr-pyrope garnets were the most abundant (65.6%). Chemical analyses revealed strong similarities to the Drybones Bay and Mud Lake kimberlites which are situated 50 to >100 km to the northeast, roughly aligned with prominent glacially streamlined landform flowsets in this field area. Results suggest there is little evidence for undetected kimberlite outcrop or sub-crop in the study area.

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