Origin of Ti-rich garnets in the groundmass of Wajrakarur field kimberlites, southern India: insights from EPMA and Raman spectroscopy

Dongre, Ashish; Viljoen, K.S.; Rao, N. V. Chalapathi; Gucsik, A.

doi:10.1007/s00710-016-0428-4

Cited by 20 publications

(12 citation statements)

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“…Sciences (IUGS) rock classification [44]. Ti-rich garnets in groundmass from Indian kimberlites have been used to classify the rocks as orangeites [25]. Those Ti-rich garnets have similar composition to the Ti-rich garnets studied in the current work, which also plot inside the field of high Ti-andradite from kimberlite-UML rocks ( Figure 6).…”

Section: Discussionmentioning

confidence: 63%

“…However, Ti-rich hydroandradite from the SK-2 kimberlite returns low total (88 wt %-96 wt %) and Si is also very low (1.6-1.9 apfu), thus suggesting the substitution of Si by OH in Z position and the existence of H2O molecules. They plot inside the field of Ti andradites from ultramafic lamprophyres [25] (Figure 6). Kassite replacing type 1 perovskite in SK-2 has a stoichiometric composition (Table 1), whereas the associated aeschynite-(Ce) tends to concentrate LREE and, to a lesser extent, Nb.…”

Section: Mineral Chemistrymentioning

confidence: 99%

Section: Mineral Chemistrymentioning

confidence: 99%

“…Primary Ti-rich garnet is considered as a key mineral for the classification of ultramafic lamprophyres, such as aillikites [24] and orangeites [25]. Ti-rich garnets classified as andradite, schorlomite, zirconian schorlomite and kimzeyite occur in the Torngat aillikite dykes [24]; kimzeyite and Ti-andradite from Aillik Bay are considered as primary magmatic minerals and are indicators of the aillikitic affinity of these rocks [26].…”

Section: Introductionmentioning

confidence: 99%

“…Compositional variation of TiO 2 , FeO T and CaO for Ti-rich garnet from SK-2 kimberlite pipe compared with Ti-rich andradites from ultramafic lamprophyres[25].…”

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confidence: 99%

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Styles of Alteration of Ti Oxides of the Kimberlite Groundmass: Implications on the Petrogenesis and Classification of Kimberlites and Similar Rocks

Melgarejo

Castillo-Oliver

2018

Minerals

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The sequence of replacement in groundmass perovskite and spinel from SK-1 and SK-2 kimberlites (Eastern Dharwar craton, India) has been established. Two types of perovskite occur in the studied Indian kimberlites. Type 1 perovskite is found in the groundmass, crystallized directly from the kimberlite magma, it is light rare-earth elements (LREE)-rich and Fe-poor and its ∆NNO calculated value is from −3.82 to −0.73. The second generation of perovskite (type 2 perovskite) is found replacing groundmass atoll spinel, it was formed from hydrothermal fluids, it is LREE-free and Fe-rich and has very high ∆NNO value (from 1.03 to 10.52). Type 1 groundmass perovskite may be either replaced by anatase or kassite along with aeschynite-(Ce). These differences in the alteration are related to different f (CO 2) and f (H 2 O) conditions. Furthermore, primary perovskite may be strongly altered to secondary minerals, resulting in redistribution of rare-earth elements (REE) and, potentially, U, Pb and Th. Therefore, accurate petrographic and chemical analyses are necessary in order to demonstrate that perovskite is magmatic before proceeding to sort geochronological data by using perovskite. Ti-rich hydrogarnets (12.9 wt %-26.3 wt % TiO 2) were produced during spinel replacement by late hydrothermal processes. Therefore, attention must be paid to the position of Ca-Ti-garnets in the mineral sequence and their water content before using them to classify the rock based on their occurrence.

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Section: Discussionmentioning

confidence: 63%

Section: Mineral Chemistrymentioning

confidence: 99%

Section: Mineral Chemistrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Compositional variation of TiO 2 , FeO T and CaO for Ti-rich garnet from SK-2 kimberlite pipe compared with Ti-rich andradites from ultramafic lamprophyres[25].…”

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confidence: 99%

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