The Main Anorthosite Layer of the West-Pana Intrusion, Kola Region: Geology and U-Pb Age Dating

Nikolay Groshev,Bartosz Karykowski

doi:10.3390/min9020071

Abstract

The West-Pana intrusion belongs to the Paleoproterozoic Fedorova-Pana Complex of the Kola Region in NW Russia, which represents one of Europe’s most significant layered complexes in terms of total platinum group element (PGE) endowment. Numerous studies on the age of the West-Pana intrusion have been carried out in the past; however, all published U-Pb isotope ages were determined using multi-grain ID-TIMS. In this study, the mineralized Main Anorthosite Layer from the upper portion of the intrusion was dated using SHRIMP-II for the first time. High Th/U (0.9–3.7) zircons gave an upper intercept age of 2509.4 ± 6.2 Ma (2σ), whereas the lower portion of the intrusion was previously dated at 2501.5 ± 1.7 Ma, which suggests an out-of-sequence emplacement of the West-Pana intrusion. Furthermore, high-grade PGE mineralization hosted by the anorthosite layer, known as “South Reef”, can be attributed to (1) downward percolation of PGE-enriched sulfide liquid from the overlying gabbronoritic magma or (2) secondary redistribution of PGEs, which may coincide with a post-magmatic alteration event recorded by low Th/U (0.1–0.9) zircon and baddeleyite at 2476 ± 13 Ma (upper intercept).

Highlights

The West-Pana intrusion represents the central block of the Paleoproterozoic Fedorova-PanaComplex located in the central part of the Kola Peninsula
High-grade platinum group element (PGE) mineralization hosted by the anorthosite layer, known as “South Reef”, can be attributed to (1) downward percolation of PGE-enriched sulfide liquid from the overlying gabbronoritic magma or (2) secondary redistribution of PGEs, which may coincide with a post-magmatic alteration event recorded by low Th/U (0.1–0.9) zircon and baddeleyite at 2476 ± 13 Ma
In terms of the crystallization history of the West-Pana intrusion and its long duration based on available age dating (Figure 8), this study shows that the geochronological questions are currently available age dating (Figure 8), this study shows that the geochronological questions are currently far from being conclusively answered

Summary

Introduction

The West-Pana intrusion represents the central block of the Paleoproterozoic Fedorova-Pana. Complex located in the central part of the Kola Peninsula. It hosts several platinum group element (PGE) deposits that are interpreted to represent contact- and reef-style mineralization (Figure 1). The Fedorova-Tundra deposit occurs at the basal contact of the complex [1], whereas the North. The West-Pana intrusion is the first layered intrusion known in Russia that hosts low-sulfide PGE mineralization at several stratigraphic levels, which share many similarities with the well-known. PGE mineralization at West-Pana occurs in two distinct layered horizons, both consisting of interlayered pyroxenite, norite, gabbronorite, and anorthosite.

Methods

Results

Discussion

Conclusion