Dating emplacement and evolution of the orogenic magmatism in the internal Western Alps: 1. The Miagliano Pluton

Swiss Journal of Geosciences

Table 2 Average composition of the rock forming minerals

Mineral phase	Biotite^a		Amphibole^b		Pyroxene^c
Phase type	Low Mg (1)	High Mg (2)	Ca–Mg hornblende		Augite	Pigeonite
Number of analyses	152	55	52		13	26
Oxides (wt%)	Average	Average	Average	SD^d	Average	Average
SiO₂	36.46	36.54	44.49	0.69	53.97	53.55
TiO₂	3.49	3.51	1.21	0.34	0.12	0.16
Al₂O₃	14.78	15.02	9.56	9.56	1.73	1.73
Fe₂O₃	4.84	4.45	6.07	1.04
FeO	17.41	16.00	12.74	1.04	14.72	24.52
MnO	0.36	0.14	0.46	0.13	0.69	1.07
MgO	9.97	11.68	9.94	0.66	15.11	16.55
CaO	0.12	0.15	11.51	0.46	12.55	1.60
Na₂O	bdl	bdl	0.83	0.24	0.22	0.16
K₂O	9.94	9.34	0.90	0.18	0.09	0.04
H₂O	4.02	3.71	2.00
Total	101.72	101.19	99.63		99.21	99.38
Cations (apfu)
Si	2.619	2.605	6.640		2.046	2.062
Ti	0.188	0.188	0.136		0.003	0.005
Al^tot	1.251	1.262	1.682		0.078	0.078
Al^IV	1.251	1.262	1.360		0.005	0.001
Al^VI			0.322		0.073	0.077
Fe³⁺	0.261	0.238	0.681
Fe²⁺	1.046	0.954	1.590		0.467	0.790
Mn	0.022	0.009	0.058		0.022	0.035
Mg	1.068	1.242	2.210		0.854	0.950
Ca	0.009	0.012	1.840		0.510	0.066
Na	0.012	0.024	0.239		0.016	0.012
K	0.911	0.849	0.172		0.004	0.002
H	0.825	0.666	2.000
Total cations	7.391	7.387	15.247		4.000	4.000

The amphiboles are given with their standard deviation
^aBiotite norm based on 11 oxygens and 2 (OH, F, Cl) using Fe³⁺/Fe_tot = 0.2
^bAmphibole norm based on 46 charges and Fe³⁺/Fe^tot = 0.3. Normalization with 23 oxygens and Fe²⁺/Fe³⁺ estimation assuming ∑13 cations
^cPyroxenes normalized to 4 cations and 12 charges
^dOne standard deviation in wt%