Contact interaction of agpaitic magmas with basement gneisses: An example of the Khibina and Lovozero Massifs

A.A. Arzamastsev, L.V. Arzamastseva, G.P. Zaraiskii

Research output

4 Citations (Scopus)

Abstract

Data on processes that occurred at contacts of large agpaitic syenite intrusions and basement gneisses obtained by the authors by studying and sampling profiles across the contacts and involve the composition of minerals, analysis of mineral assemblages, isotopic dating of the processes, and analysis of the behavior of major, volatile, and trace elements in rocks near the contact. The contact zones of the massifs were determined to consist of products of contact interaction during the early and late magmatic stages and provide a record of successive stages of a continuous process of gneiss transformations, starting with the filling of the magmatic reservoir with melt and ending with late- and postmagmatic processes related to the development of a system of alkaline veins and pegmatite bodies in the gneisses. Early alkaline metasomatic processes in the Khibina Massif were local, controlled by diffusion, and were induced by the immediate thermal and chemical effect of alkaline melts on the gneisses. In the Lovozero Massif, metasomatism was related predominantly to the development of postmagmatic veins at 359 ± 5 Ma, was controlled by infiltration, and proceeded immediately after the consolidation of the main intrusive series. The metasomatic transformations during the early and late magmatic stages under the effect of agpaitic melts on gneisses predetermined different closure conditions and, correspondingly, different behaviors of the Rb-Sr and Sm-Nd isotopic systems during the contact processes: while the interaction of agpaitic melts with gneisses has modified the (87Sr/86Sr)(T = 370 Ma) ratio via the enrichment of radiogenic Sr in the host Archean rocks, the Sm-Nd isotopic characteristics of the syenites in the inner contact zone and veins preserved their mantle values, which corresponded to the average ones for rocks in the central parts of the intrusion. Experimental data, model simulations, and natural observations testify that Nb, Ta, Zr, Hf, and REE were mobile in the contact interaction zone with agpaitic melts. With regard for data on the fluid regime of the agpaitic melts and the concentrations of volatile components in the contact zones, we believe that the main role in the transfer of REE and HFSE during contact metasomatism could be played by their ligands with F-, Cl-, and SO4 2-.
Original languageEnglish
Pages (from-to)109-133
Number of pages25
JournalPetrology
Volume19
Issue number2
DOIs
Publication statusPublished - 2011
Externally publishedYes

Fingerprint

Rocks
melt
Minerals
contact zone
Trace Elements
metasomatism
Infiltration
Consolidation
Data structures
rare earth element
rock
Sampling
Ligands
volatile element
Fluids
syenite
pegmatite
mineral
Chemical analysis
gneiss

Scopus subject areas

  • Geochemistry and Petrology

Cite this

@article{92a96a3c776b4725b7aca7e80652ad6a,
title = "Contact interaction of agpaitic magmas with basement gneisses: An example of the Khibina and Lovozero Massifs",
abstract = "Data on processes that occurred at contacts of large agpaitic syenite intrusions and basement gneisses obtained by the authors by studying and sampling profiles across the contacts and involve the composition of minerals, analysis of mineral assemblages, isotopic dating of the processes, and analysis of the behavior of major, volatile, and trace elements in rocks near the contact. The contact zones of the massifs were determined to consist of products of contact interaction during the early and late magmatic stages and provide a record of successive stages of a continuous process of gneiss transformations, starting with the filling of the magmatic reservoir with melt and ending with late- and postmagmatic processes related to the development of a system of alkaline veins and pegmatite bodies in the gneisses. Early alkaline metasomatic processes in the Khibina Massif were local, controlled by diffusion, and were induced by the immediate thermal and chemical effect of alkaline melts on the gneisses. In the Lovozero Massif, metasomatism was related predominantly to the development of postmagmatic veins at 359 ± 5 Ma, was controlled by infiltration, and proceeded immediately after the consolidation of the main intrusive series. The metasomatic transformations during the early and late magmatic stages under the effect of agpaitic melts on gneisses predetermined different closure conditions and, correspondingly, different behaviors of the Rb-Sr and Sm-Nd isotopic systems during the contact processes: while the interaction of agpaitic melts with gneisses has modified the (87Sr/86Sr)(T = 370 Ma) ratio via the enrichment of radiogenic Sr in the host Archean rocks, the Sm-Nd isotopic characteristics of the syenites in the inner contact zone and veins preserved their mantle values, which corresponded to the average ones for rocks in the central parts of the intrusion. Experimental data, model simulations, and natural observations testify that Nb, Ta, Zr, Hf, and REE were mobile in the contact interaction zone with agpaitic melts. With regard for data on the fluid regime of the agpaitic melts and the concentrations of volatile components in the contact zones, we believe that the main role in the transfer of REE and HFSE during contact metasomatism could be played by their ligands with F-, Cl-, and SO4 2-.",
author = "A.A. Arzamastsev and L.V. Arzamastseva and G.P. Zaraiskii",
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Contact interaction of agpaitic magmas with basement gneisses: An example of the Khibina and Lovozero Massifs. / Arzamastsev, A.A.; Arzamastseva, L.V.; Zaraiskii, G.P.

In: Petrology, Vol. 19, No. 2, 2011, p. 109-133.

Research output

TY - JOUR

T1 - Contact interaction of agpaitic magmas with basement gneisses: An example of the Khibina and Lovozero Massifs

AU - Arzamastsev, A.A.

AU - Arzamastseva, L.V.

AU - Zaraiskii, G.P.

PY - 2011

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N2 - Data on processes that occurred at contacts of large agpaitic syenite intrusions and basement gneisses obtained by the authors by studying and sampling profiles across the contacts and involve the composition of minerals, analysis of mineral assemblages, isotopic dating of the processes, and analysis of the behavior of major, volatile, and trace elements in rocks near the contact. The contact zones of the massifs were determined to consist of products of contact interaction during the early and late magmatic stages and provide a record of successive stages of a continuous process of gneiss transformations, starting with the filling of the magmatic reservoir with melt and ending with late- and postmagmatic processes related to the development of a system of alkaline veins and pegmatite bodies in the gneisses. Early alkaline metasomatic processes in the Khibina Massif were local, controlled by diffusion, and were induced by the immediate thermal and chemical effect of alkaline melts on the gneisses. In the Lovozero Massif, metasomatism was related predominantly to the development of postmagmatic veins at 359 ± 5 Ma, was controlled by infiltration, and proceeded immediately after the consolidation of the main intrusive series. The metasomatic transformations during the early and late magmatic stages under the effect of agpaitic melts on gneisses predetermined different closure conditions and, correspondingly, different behaviors of the Rb-Sr and Sm-Nd isotopic systems during the contact processes: while the interaction of agpaitic melts with gneisses has modified the (87Sr/86Sr)(T = 370 Ma) ratio via the enrichment of radiogenic Sr in the host Archean rocks, the Sm-Nd isotopic characteristics of the syenites in the inner contact zone and veins preserved their mantle values, which corresponded to the average ones for rocks in the central parts of the intrusion. Experimental data, model simulations, and natural observations testify that Nb, Ta, Zr, Hf, and REE were mobile in the contact interaction zone with agpaitic melts. With regard for data on the fluid regime of the agpaitic melts and the concentrations of volatile components in the contact zones, we believe that the main role in the transfer of REE and HFSE during contact metasomatism could be played by their ligands with F-, Cl-, and SO4 2-.

AB - Data on processes that occurred at contacts of large agpaitic syenite intrusions and basement gneisses obtained by the authors by studying and sampling profiles across the contacts and involve the composition of minerals, analysis of mineral assemblages, isotopic dating of the processes, and analysis of the behavior of major, volatile, and trace elements in rocks near the contact. The contact zones of the massifs were determined to consist of products of contact interaction during the early and late magmatic stages and provide a record of successive stages of a continuous process of gneiss transformations, starting with the filling of the magmatic reservoir with melt and ending with late- and postmagmatic processes related to the development of a system of alkaline veins and pegmatite bodies in the gneisses. Early alkaline metasomatic processes in the Khibina Massif were local, controlled by diffusion, and were induced by the immediate thermal and chemical effect of alkaline melts on the gneisses. In the Lovozero Massif, metasomatism was related predominantly to the development of postmagmatic veins at 359 ± 5 Ma, was controlled by infiltration, and proceeded immediately after the consolidation of the main intrusive series. The metasomatic transformations during the early and late magmatic stages under the effect of agpaitic melts on gneisses predetermined different closure conditions and, correspondingly, different behaviors of the Rb-Sr and Sm-Nd isotopic systems during the contact processes: while the interaction of agpaitic melts with gneisses has modified the (87Sr/86Sr)(T = 370 Ma) ratio via the enrichment of radiogenic Sr in the host Archean rocks, the Sm-Nd isotopic characteristics of the syenites in the inner contact zone and veins preserved their mantle values, which corresponded to the average ones for rocks in the central parts of the intrusion. Experimental data, model simulations, and natural observations testify that Nb, Ta, Zr, Hf, and REE were mobile in the contact interaction zone with agpaitic melts. With regard for data on the fluid regime of the agpaitic melts and the concentrations of volatile components in the contact zones, we believe that the main role in the transfer of REE and HFSE during contact metasomatism could be played by their ligands with F-, Cl-, and SO4 2-.

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DO - 10.1134/S0869591111020032

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SN - 0869-5911

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