Mineralogical and geochemical characteristics of the NNW-NNE trending Libiri doleritic dyke swarm of the Paleoproterozoic Liptako basement (West Niger): Genesis and magmatic evolution

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Table 4

Selected points are representative electron microprobe analysis results of pyroxene.

Samples	SD	SD	SD	TD1	TD1	SLB	TD2

Mineral	Augite	Pigeonite	Hypersthene	Augite	Diopside	Pigeonite	Augite
SiO₂	52.43	51.98	53.88	51.3	49.93	52.92	51.22
Na₂O	0.18	0.06	0.03	0.29	0.57	0.11	0.30
MgO	17.00	20.42	28.12	15.65	9.07	20.49	14.98
Al₂O₃	1.74	1.49	2.72	2.56	1.40	1.48	2.10
K₂O	0.00	0.02	0.00	0.01	0.00	0.00	0.00
CaO	16.51	6.85	2.16	18.67	21.37	7.58	17.79
TiO₂	0.30	0.32	0.15	0.70	0.20	0.28	0.72
Cr₂O₃	0.17	0.20	0.46	0.11	0.02	0.11	0.02
MnO	0.25	0.30	0.16	0.24	0.71	0.39	0.32
FeO	10.87	17.67	11.36	9.5	15.45	16.18	11.25
NiO	0.03	0.03	0.10	0.05	0.00	0.04	0.04
Total	99.48	99.34	99.14	99.08	98.85	99.58	98.74
Numbers of ions based on 6 oxygens
Al^IV	0.04	0.053	0.067	0.078	0.044	0.036	0.063
Si	1.94	1.946	1.932	1.922	1.956	1.963	1.937
Na	0.01	0.004	0.002	0.021	0.043	0.007	0.022
Mg	0.94	1.140	1.503	0.874	0.53	1.133	0.844
Al^VI	0.028	0.012	0.047	0.035	0.021	0.028	0.030
K	0.00	0.00	0.000	0.000	0.000	0.000	0.00
Ca	0.65	0.274	0.083	0.75	0.897	0.301	0.720
Ti	0.008	0.009	0.004	0.02	0.006	0.007	0.020
Cr	0.005	0.005	0.013	0.003	0.001	0.003	0.000
Mn²⁺	0.007	0.009	0.004	0.008	0.024	0.012	0.010
Fe²⁺	0.338	0.5534	0.3407	0.298	0.506	0.502	0.355
Total	4.004	4.009	3.998	4.009	4.027	3.997	4.0052
Al^IV/Al^VI	1.652	4.341	1.441	2.228	2.095	1.257	2.058
Wo (Ca)	0.338	0.139	0.043	0.3886	0.4585	0.1546	0.3732
En (Mg)	0.4842	0.5764	0.7782	0.4532	0.2707	0.5815	0.4373
Fs (Fe)	0.1777	0.2846	0.1789	0.1583	0.2708	0.2639	0.1895

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