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AmphiCalc-1
AmphiCalc-1 automatically calculates amphibole composition and classification from microprobe analyses. For this purpose, AmphiCalc-1 provides several calculation routines ( for more information see below ).
The amphibole group (short: amphiboles) includes minerals from the mineral class of silicates and germanates (compounds of germanium), which are structurally characterized by double chains of corner-sharing Si₂O₄ tetrahedra and whose composition satisfies the following generalized molecular formula:
A₀₋₁B₂C₅T₈O₂₂(OH)₂
In this structural formula, the capital letters A, B, C and T represent different positions in the amphibole structure. They are occupied by the following cations. The dominant cations at the individual positions are highlighted in bold:
- A: Spaces, Na⁺, K⁺, Ba²⁺, Sr²⁺, Ca²⁺, Li⁺
- B: Ca²⁺, Na⁺, Mg²⁺, Fe²⁺, Mn²⁺, Li⁺, Sr²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mg²⁺, Pb²⁺, Cu, Zr, Mn³⁺, Cr³⁺, V, Fe³⁺
- C: Mg²⁺, Fe²⁺, Mn²⁺, Li⁺, Al³⁺, Zn²⁺, Ni²⁺, Co²⁺, Ti4⁺, Fe³⁺, V, Cr³⁺, Mn³⁺, Zr
- T: Si⁴⁺, Al³⁺, Ti⁴⁺
- Instead of the hydroxyl group (OH), amphiboles also contain F⁻, Cl⁻, O²⁻
AmphiCalc-1: Amphibole – Composition and classification
Amphiboles are the mineral group with the greatest chemical variability. Amphiboles occur worldwide in many different parageneses and geological environments. They are an important component of both magmatic and metamorphic rocks with a wide variety of compositions and formation conditions. Various minerals in this group are referred to as asbestos.
The AmphiCalc-1 program automatically calculates the formula occupancy, the Fe²⁺ and Fe³⁺ distribution, as well as other parameters of amphiboles from microprobe analyses. The following diagrams are automatically created: Leake diagram, ACF diagram, AFM diagram.
Due to the complexity of amphiboles, AphiCalc-1 provides several calculation routines. You can select these by clicking on the respective name (e.g. "Amp13RM") in the table below:
- Amp13RM: Calculation on the basis of 13 cations without Na, K, Mn und Ca.
- Amp13RX: Calculation on the basis of 13 cations without Na, K, Ca.
- Amp15KX: Calculation on the basis of 15 cations without K; Ca only on position B.
- Amp15KC: Calculation on the basis of 15 cations without K; Ca also on position C.
- Amp15RX: Calculation on the basis of 15 cations without Na, K; Ca only on position B.
Literature
- Deer, W.A., Howie, R.A. & Zussman, J. (1992): An introduction to the rock-forming minerals. – Longman Scientific & Technical, Harlow, 2nd edition 1992: 696 p.
- Ehlers, E.G. and Blatt, H. (1982): Petrology: Igneous, Sedimentary and Metamorphic. W. H. Freeman, New York, 732 p.
- Wikipedia
- Further literature can be found under the individual calculation routines.