Kimberlite

Morphology and Volcanology

• Kimberlite structures are emplaced as carrot-shaped, vertical intrusions termed pipes.
• The carrot shape is formed due to a complex intrusive process of kimberlitic magma.
• Kimberlite classification is based on differing rock facies associated with specific magmatic activity.
• The morphology of kimberlite pipes is the result of explosive diatreme volcanism.
• Kimberlite pipes can have a sheeted dyke complex and range in diameter from 75 meters to 1.5 kilometers.

Petrology

• The location and origin of kimberlitic magmas are subjects of contention.
• Kimberlites have been classified into basaltic and micaceous varieties based on petrographic observations.
• Later revisions led to the classification of group I and group II kimberlites.
• Group II kimberlites were reclassified as orangeites due to their closer affinities to lamproites.
• Group I kimberlites are CO-rich ultramafic potassic igneous rocks with specific mineral assemblages.

Group I Kimberlites

• Group I kimberlites are dominated by primary forsteritic olivine and carbonate minerals.
• They exhibit a distinctive inequigranular texture caused by macrocrystic and megacrystic phenocrysts.
• The groundmass mineralogy is dominated by carbonate and significant amounts of forsteritic olivine.
• Group I kimberlites have a fine- to medium-grained groundmass.
• They contain trace minerals such as magnesian ilmenite, chromium pyrope, and phlogopite.

Olivine Lamproites

• Olivine lamproites were previously called group II kimberlites or orangeites.
• They are ultrapotassic, peralkaline rocks rich in volatiles.
• Olivine lamproites are characterized by phlogopite macrocrysts and microphenocrysts.
• The groundmass micas in olivine lamproites vary in composition.
• Primary phases in the groundmass include zoned pyroxenes, spinel-group minerals, and Sr- and REE-rich minerals.

Kimberlitic Indicator Minerals

• Kimberlites contain mineral species that indicate formation under high pressure and temperature.
• These minerals serve as indicators of mantle conditions.
• Some of these indicator minerals include chromi
• The presence of these minerals is used in diamond exploration.
• The chemical compositions of these minerals provide valuable information about the deep mantle.

Kimberlite Data Sources