A revised program for microprobe-derived amphibole analyses using the IMA rules

Abstract

A Microsoft QUICKBASIC program with the code name NEWAMPHCAL has been written to calculate the structural formulae of amphibole analyses taken from electron-microprobe, and to determine the classification parameters with the prefixes and modifiers according to the procedures proposed by the International Mineralogical Association (IMA) 1997 amphibole nomenclature scheme. The program, which came up with four Al-in hornblende geobarometers, is applicable to plutonic and its associated volcanic rocks including amphibole–biotite–quartz–plagioclase–ortochlase–sphene–FeTi oxides. An amphibole–plagioclase geothermometer for particular calcic amphiboles also is incorporated into the program structure. NEWAMPHCAL has been tested for determination and classification of numerous amphibole analyses compiled from literature. Depending on the evaluations of selected amphibole analyses by using NEWAMPHCAL program, it was determined that approximately 15% amphibole names were changed compared to the author’s IMA 1978 findings. The most important variation in amphibole names has been observed in the calcic amphibole group. This program permits the user data entry, their storage, and calculation and plotting of microprobe amphibole analyses. NEWAMPHCAL plots the calculated chemical parameters on one ternary and seventeen different binary diagrams for amphibole classification. This software, with well-designed screen forms, stores all the calculated results in comma delimited ASCII file format and thus permits the user to process the program outputs for further spreadsheet applications. A menu-driven and easy to use program runs on IBM-compatible microcomputers under DOS and Windows systems with the minimum hardware requirements. The compiled form of NEWAMPHCAL takes approximately 398 kilobytes together with the test data.