The role of the antigorite + brucite to olivine reaction in subducted serpentinites (Zermatt, Switzerland)

Swiss Journal of Geosciences

Table 1 Major and minor element composition of magnetite, Cr-magnetite, Cr-spinel

Sample	FA					Ol28				MF	Ol26
wt%	Polygon	Vein	Core	Core	Rim	Core	Core	Rim	Core	Polygon	Vein
TiO₂	0.05	0.06	0.14	0.12	0.06	0.14	0.15	0.04	0.20	0.06	0.12
Al₂O₃	b.d.	0.15	0.27	0.03	0.03	4.38	0.23	0.01	26.82	0.09	0.02
Cr₂O₃	1.55	3.94	24.53	8.11	4.06	35.95	45.78	3.15	40.34	3.08	1.03
Fe₂O₃	68.81	67.14	46.33	63.07	66.40	31.90	27.39	67.10	4.50	67.80	69.10
FeO	24.60	23.49	15.62	21.62	24.04	15.93	15.87	25.61	10.51	23.07	24.07
MnO	0.31	0.58	2.77	0.82	0.45	2.16	2.86	0.23	1.45	0.44	0.46
NiO	0.32	0.29	0.24	0.37	0.23	0.19	0.06	0.33	0.06	0.64	0.43
MgO	3.70	4.47	7.92	5.50	4.07	9.24	8.64	3.16	15.89	4.06	3.96
CaO	b.d.	0.01	0.59	b.d.	0.01	b.d.	0.01	0.02	0.01	b.d.	b.d.
Total	99.35	100.15	99.01	99.71	99.36	99.93	101.05	99.68	99.79	99.45	99.28
Ti	0.002	0.002	0.004	0.003	0.002	< 0.001	0.040	< 0.001	< 0.001	0.002	0.003
Al	–	0.007	0.011	0.001	0.001	0.180	0.001	< 0.001	0.940	0.004	0.001
Cr	0.046	0.116	0.698	0.237	0.120	0.980	1.263	0.090	0.950	0.091	0.031
Fe³	1.950	1.873	1.254	1.751	1.873	0.830	0.719	1.900	0.100	1.909	1.955
Fe²	0.775	0.728	0.470	0.667	0.754	0.460	0.463	0.810	0.260	0.722	0.757
Mn	0.010	0.018	0.084	0.026	0.014	0.060	0.085	0.010	0.040	0.014	0.015
Ni	0.010	0.009	0.007	0.011	0.007	0.010	0.002	0.010	< 0.001	0.019	0.013
Mg	0.208	0.247	0.425	0.302	0.227	0.480	0.449	0.180	0.700	0.226	0.222
Ca	–	< 0.001	0.023	–	< 0.001	–	< 0.001	< 0.001	< 0.001	–	–
Mg#	20.7	24.7	43.1	30.1	22.7	47.5	42.2	17.8	70.0	23.1	22.0
Cr#	1.000	0.946	0.984	0.994	0.989	0.845	0.961	1.000	0.503	0.957	0.965

CaO and SiO₂ mass fractions derive from secondary fluorescence and or beam deflection
Normalized to 3 cations and 4 oxygens Mg# = (Mg/(Mg + Fe + Ni + Mn))*100
Cr# = Cr/(Cr + Al)
b.d. below detection limit