Nyerereite from carbonatite rocks at Vulture volcano: implications for mantle metasomatism and petrogenesis of alkali carbonate melts Research Article

Abstract

Vulture volcano displays a wide range of mafic to alkaline, carbonate-, and/or CaO-rich volcanic rocks, with subvolcanic and plutonic rocks together with mantle xenoliths in pyroclastic ejecta. The roles of magmatic volatiles such as CO 2 , S, and Cl have been determined from compositions and trapping temperatures of inclusions in phenocrysts, which include the Na-K-Ca-carbonate nyerereite within melilite. We surmise that this alkali carbonate crystallised from an appropriate carbonatitic melt at relatively high temperature. Carbonatitic metasomatic features are traceable throughout many of the mantle xenoliths, and various carbonatitic components are found in the late stage extrusive suite. There is no evidence that alkali carbonatite developed as a separate magma, but it may have been an important evolutionary stage. We compare the rare occurrence of nyerereite at Vulture with other carbonatites and with an unaltered kimberlite from the Udachnaya pipe. We review the evidence at Vulture for associated carbonatitic metasomatism in the mantle, and we suggest that low viscosity alkali carbonatitic melts may have a primary and much deeper origin than previously considered.

Silicate-carbonate-salt liquid immiscibility and origin of the sodalite-haüyne rocks: study of melt inclusions in olivine foidite from Vulture volcano, S. Italy

“…Clinopyroxene phenocrysts show glass inclusions with sulphide globules and crystal inclusions of apatite, haüyne, and magnetite. Particularly interesting is the occurrence of extrusive carbonatite at Vallone Toppo del Lupo, where nyerereite inclusions were found in melilite [2]. Data from carbonatite also show that immiscible Na-carbonate existed in the magmatic system [2].…”

“…As to the origin of carbonatites, most researchers think that two-phase silicatecarbonate immiscibility plays a leading role in their formation (see discussion in Stoppa et al [2]). This assumption is supported by numerous experimental data, results of studies of melt inclusions in minerals, and geological observations.…”

“…Abundant occurrences of silicate-carbonate and multiphase silicate-carbonate-salt immiscibility were detected in thermometric experiments with melt inclusions in the minerals of different alkaline rocks [2,[13][14][15][16][17][18][19][20][21][22][23]. Of especial interest was multiphase carbonate-salt immiscibility in silicate-salt inclusions in perovskite of melilite rocks from the Krestovskaya intrusion (Polar Siberia).…”

Calcium-aluminum-silicate-hydrate “cement” phases and rare Ca-zeolite association at Colle Fabbri, Central Italy

“…Other examples of wollastonite melilitolite are from Mt. Vulture [5], a mafic alkaline volcano located in the Lucania Region of Italy, which displays a wide range of mafic to alkaline, Ca-rich volcanic rocks, with melilitolite, ijolite, soevite, Ne-syenite ejecta together with mantle xenoliths [6].…”

“…Carbonatites and high-calcium igneous rocks, such as melilitite/melilitolite and ijolite, also contain CSH minerals [17]. Ettringite has been recently reported from Vulture carbonatite [6].…”