# Sulfur and REE zoning in apatite: The example of the Colli Albani magmatic system

## TL;DR

This study examines sulfur and rare earth element zoning in apatite crystals from the Colli Albani volcanic system, revealing core-rim compositional variations linked to magmatic processes and mineral phase absence.

## Contribution

It provides detailed geochemical analysis of apatite zoning in alkaline rocks, highlighting the influence of mineral assemblage on element distribution in magmatic systems.

## Key findings

- Apatite crystals are SrO-rich fluorapatite with up to 4.6 wt% SrO.
- Core-rim zoning shows rims enriched in Si, S, and REE, cores in Ca and P.
- REE contents in apatite account for over 95% of total REE budget.

## Abstract

We investigate the distribution of major and trace elements in apatite crystals hosted in granular alkaline rocks composed mainly of leucite and clinopyroxene, representative of the hypabyssal crystallization of a magma body in the Quaternary ultra-potassic Colli Albani Volcanic District (CAVD), which was emplaced into thick limestone units along the Tyrrhenian margin of Italy. Results show that the analyzed crystals are the SrO-richest (up to 4.6 wt%) fluorapatite (F =2.6-3.7 wt%) of the Italian alkaline rocks. The strontium enrichment is caused by the lack of other Sr-compatible mineral phases, such as plagioclase, alkali feldspar and melilite, in these leucite- and clinopyroxene-bearing rocks. The studied samples show core-rim zoning with rims enriched in Si, S, and REE whereas the cores are enriched in Ca and P. The LREE-oxides contents of apatite, reaching 4.2 wt%, represent more than 95% of the total REE budget; SiO2 contents range from 1.3 to 3.6 wt%, and SO3 concentrations between 0.6 and 1.4 wt%.

---
Source: https://tomesphere.com/paper/1812.11040