DISTINCTION BETWEEN MAGMATIC AND HYDROTHERMAL SIGNATURES IN APATITES FROM NORTH PORTUGAL - CATHODOLUMINESCENCE, SEM AND ELECTRON-MICROPROBE STUDY

• Type: Article in International Scientific Journal
• Date: 1994

Authors

BLANC, P (Author) Other; ROGER, G (Author) Other; COUTO, H (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: BULLETIN DE LA SOCIETE GEOLOGIQUE DE FRANCE

Vol. 165

Pages: 329-339

ISSN: 0037-9409

Publisher: SOC GEOL FRANCE

Indexing

ISI Web of Knowledge - 7 Citations

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Authenticus ID: P-001-KKW

Abstract (EN): Scanning electron microprobe (SEM), electron probe micro analysis (EPMA) and cathodoluminescence (CL) were performed for the study of fluorapatite crystals from samples collected in northwestern Portugal: in syn- to late-tectonic Hercynian granites, in one Sn-bearing aplite-pegmatite vein, and in two Sb-Au bearing quartz veins. Two types of CL spectra are distinguished: (1) apatite with a strong yellow luminescence exhibits a Mn broad band spectrum at 575 nm: (2) apatite with a weak pink-yellow to pale violet luminescence shows a spectrum with narrow peaks characteristic of rare earth elements (REE). EPMA reveal two different chemical signatures: apatites characterized by high grades in Mn (MnO less-than-or-equal-to 7,3%), Fe and Sr, and by the presence of La and Ce, corresponding to type 1 spectra; apatites with very low Mn and Fe concentrations, weak Sr-concentrations, higher Y and Si contents, and the presence of Nd, Sm and Gd. Some peaks of type 2 spectra are due to Dy, Eu, Sm, Tb and Gd. So, the study of apatite by CL optical observation and by CL spectrometry results in the distinction of differences that were not detectable by the use of optical microscopy or by SEM, and these data were a useful guide for microprobe analysis. The correlation between CL and chemical composition is a cheap and efficient tool for identification of apatite geochemical signature. That tool could be improved by a better knowledge of trace elements activators, especially REE, by mean of synthetic doped crystals. Much less than Magmatic much greater than signature is mainly characterized by high concentrations of Mn, Fe and Sr in apatite of type 1, and much less than hydrothermal much greater than signature by high contents in Y and Si in apatite of type 2. The apatites from Ribeiro da Igreja Sb-Au bearing quartz vein show the transition between these two signatures. These results support the hypothesis of a genetic relation between Sb-Au quartz veins, Sn-W bearing veins, and a tardi-plutonic hydrothermal activity.

Language: French

Type (Professor's evaluation): Scientific

No. of pages: 11