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The adamas of Ancient peoples is proved to be the precious diamond. An ancient and uconventional diamond occurrence, the mines of Philippi in Macedonia (northern Greece), is geologically explained here. The most probable source is believed to be flat subduction-related (shoshonitic) lamprophyres that originated at a depth of >110 km within the mantle in the diamond stability field. The thick lithospheric mantle beneath Greece supports the occurrence of diamondiferous lamprophyric rocks in this area. However, no lamprophyre outcrops have been found, except for a few lamprophyre dikes 14 km SE of Philippi. Another explanation for the occurrence would implicate detrital diamonds that have been preserved in the local greenschist facies rocks. The XRD analysis of Philippi paragneiss showed the existence of the mantle mineral magnesiowüstite, which is a possible diamond indicator. The Philippi occurrence deserves detailed investigation involving alluvial sampling and ground magnetic surveys to locate the diamond source.

This paper addresses geochemical and petrological aspects of two outcropping kimberlites (5023 and 5119) of the Gooty cluster, emplaced in carbonate sediments of Vempalli Formation of lower Cuddapah basin at Krishtipadu, Anantapur district, Andhra Pradesh, southern India. These pipes were discovered by the Rio Tinto Exploration Group in the recent past. The 5023 kimberlite is enriched in olivine and serpentine while the 5119 pipe possesses haematitised olivine pseudomorphs. The field, textural characteristics and whole rock geochemistry qualify both the pipes for hypabyssal kimberlite breccias of Group-I type similar to world's classical occurrences. The carbon and oxygen stable isotope data, aided with field and petrological studies, indicates existence of possible carbonatite (sovite) phase associated with the 5119 kimberlite. The two kimberlites appear to be originated from a low degree of partial melting ranging from 0.5 to 2.5%. Enrichment of LREE with a high LREE/HREE ratio indicates fractionation at the mantle source region. Whole rock geochemistry supports their diamondiferous nature. Presence of crustal xenoliths post-dates subsequent emplacement of the two pipes to lower Cuddapah sedimentation (2.4 Ga), manifesting kimberlite magmatism. These pipes are the only known Group-I kimberlites from the Proterozoic Cuddapah Basin and therefore warrant detailed investigations.

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