Geochemical Characteristics and Provenance Analysis of Clastic Reservoirs in Sub-Salt Rift Period in Gabon Basin

doi:10.19657/j.geoscience.1000-8527.2023.044

Abstract

Abstract:

Provenance of the subsalt reservoir in the Gabon basin mainly comes from the upper crust, mainly felsic rocks, together with the ancient metavolcanic-sedimentary rocks under Proterozoic convergence and subduction tectonic setting. There is certain amount of mixing of alkaline basalt and granite, with good inheritance of provenance composition and tectonic background of the source region, and no obvious difference. Differences in major and trace element compositions in Gamba and Dentale formations are unobvious. Analyses of major elements, trace elements and rare earth elements show that the provenance mainly comes from the convergence and subduction zones of active continental margin, with trench-Arc basin system. They are featured by low SiO₂ and Na₂O, similar to the Katanga supergroup and Pore group deposited in Proterozoic back-Arc basin on the western margin of Congo Craton. The Delonggu group is related to each other. The sub-salt reservoirs in the basin have high total REE content. The REE distribution pattern is related to the Proterozoic Lufili orogenic belt on the western margin of Congo Craton, but differs greatly from the Proterozoic Archean tectonic belts of San Francisco Craton in South America. This indicates that they are not the main provenance of the basin, and that the provenance is mainly the Congo Craton.

Key words: Gabon basin, subsalt clastic reservoir, major element, trance element, REE pattern

CLC Number:

P588.21

CHEN Quanhong, YANG Huaizhong, ZHAO Hongyan, ZHANG Ke, HUANG Haibin, GUO Jiaming, LIU Xinying, YUAN Ye. Geochemical Characteristics and Provenance Analysis of Clastic Reservoirs in Sub-Salt Rift Period in Gabon Basin[J]. Geoscience, 2023, 37(05): 1385-1397.

Figures/Tables 15

References 28

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地层及构造环境		SiO₂	TiO₂	Al₂O₃	TFe₂O₃	MnO	MgO	CaO	Na₂O	K₂O	P₂O₅	LOI	TFe₂O₃+ MgO	Al₂O₃/ SiO₂	K₂O/ Na₂O	Al₂O₃/ (CaO+Na₂O)	TFe₂O₃/ K₂O
Gamba 组	L1(6)	52.2	00.89	15.05	5.68	0.04	3.32	1.90	0.47	4.38	0.32	11.41	09.00	0.29	10.35	06.43	1.30
	L2(9)	47.03	00.68	12.34	4.77	0.07	3.07	5.00	0.59	3.35	0.28	16.40	07.84	0.27	05.84	02.91	1.42
	N1	52.94	00.90	15.05	5.27	0.08	2.63	2.09	1.23	4.12	0.29	10.71	07.90	0.28	03.34	04.53	1.28
	Tsi(2)	64.52	0	21.54	3.73	0	4.17	0.33	0.46	4.65	0	-	07.90	0.34	10.13	28.36	0.80
Dentale 组	L1	56.02	0.81	14.70	4.74	0.05	2.80	1.98	0.47	5.25	0.30	08.91	07.54	0.26	11.11	06.00	0.90
	L2	53.61	0.74	13.16	4.49	0.03	2.41	2.20	1.03	4.31	0.28	11.22	06.90	0.25	04.20	04.08	1.04
	N1(6)	53.86	0.86	13.90	5.78	0.06	2.67	2.26	1.61	4.11	0.32	09.99	08.45	0.26	02.57	03.60	1.41
	Oba(2)	68.09	0	13.10	3.55	0	7.18	0	0.46	5.29	0	-	10.73	0.22	09.40	26.59	0.67
OIA	58.83	01.06	17.11	01.95	0.15	3.65	5.83	4.10	1.60	0.26	5.52	11.73	00.29	0.39	01.72	01.22
CIA	70.69	00.64	14.04	01.43	0.10	1.97	2.68	3.12	1.89	0.16	3.05	06.79	00.20	0.61	02.42	00.76
ACM	73.86	00.46	12.89	01.30	0.10	1.23	2.48	2.77	2.90	0.09	1.58	04.63	00.17	1.05	02.46	00.45
PCM	81.95	00.49	08.41	01.32	0.05	1.39	1.89	1.07	1.71	0.12	1.76	02.89	00.10	1.60	02.84	00.77
上地壳	66	00.64	15.20	04.50	0.08	2.20	4.20	3.90	3.40	0.15	-	07.15	00.23	0.87	01.88	01.32

地层及构造环境		SiO₂	TiO₂	Al₂O₃	TFe₂O₃	MnO	MgO	CaO	Na₂O	K₂O	P₂O₅	LOI	TFe₂O₃+ MgO	Al₂O₃/ SiO₂	K₂O/ Na₂O	Al₂O₃/ (CaO+Na₂O)	TFe₂O₃/ K₂O
Gamba 组	L1(6)	52.2	00.89	15.05	5.68	0.04	3.32	1.90	0.47	4.38	0.32	11.41	09.00	0.29	10.35	06.43	1.30
	L2(9)	47.03	00.68	12.34	4.77	0.07	3.07	5.00	0.59	3.35	0.28	16.40	07.84	0.27	05.84	02.91	1.42
	N1	52.94	00.90	15.05	5.27	0.08	2.63	2.09	1.23	4.12	0.29	10.71	07.90	0.28	03.34	04.53	1.28
	Tsi(2)	64.52	0	21.54	3.73	0	4.17	0.33	0.46	4.65	0	-	07.90	0.34	10.13	28.36	0.80
Dentale 组	L1	56.02	0.81	14.70	4.74	0.05	2.80	1.98	0.47	5.25	0.30	08.91	07.54	0.26	11.11	06.00	0.90
	L2	53.61	0.74	13.16	4.49	0.03	2.41	2.20	1.03	4.31	0.28	11.22	06.90	0.25	04.20	04.08	1.04
	N1(6)	53.86	0.86	13.90	5.78	0.06	2.67	2.26	1.61	4.11	0.32	09.99	08.45	0.26	02.57	03.60	1.41
	Oba(2)	68.09	0	13.10	3.55	0	7.18	0	0.46	5.29	0	-	10.73	0.22	09.40	26.59	0.67
OIA	58.83	01.06	17.11	01.95	0.15	3.65	5.83	4.10	1.60	0.26	5.52	11.73	00.29	0.39	01.72	01.22
CIA	70.69	00.64	14.04	01.43	0.10	1.97	2.68	3.12	1.89	0.16	3.05	06.79	00.20	0.61	02.42	00.76
ACM	73.86	00.46	12.89	01.30	0.10	1.23	2.48	2.77	2.90	0.09	1.58	04.63	00.17	1.05	02.46	00.45
PCM	81.95	00.49	08.41	01.32	0.05	1.39	1.89	1.07	1.71	0.12	1.76	02.89	00.10	1.60	02.84	00.77
上地壳	66	00.64	15.20	04.50	0.08	2.20	4.20	3.90	3.40	0.15	-	07.15	00.23	0.87	01.88	01.32

构造环境及层段		La	Ce	Nd	∑REE	LREE/HREE	δEu	(La/Yb)_N	La/Y	La/Yb
大洋岛弧	杂砂岩^*	8.72±2.5	22.5±35.9	11.36±2.9	58±10	3.8±0.9	1.04±0.11	2.8±0.9	0.48±0.12	4.2±1.3
大陆岛弧	杂砂岩^*	24.4±2.3	50.5±4.3	20.8±1.6	146±20	7.7±1.7	0.79±0.13	7.5±2.5	1.02±0.07	7.5±2.5
活动陆缘	杂砂岩^*	33.0±4.5	72.7±9.8	25.4±3.4	186	9.1	0.6	8.5	1.33±0.09	8.5
被动陆缘	杂砂岩^*	44.5±5.8	71.9±11.5	29.0±5.03	210	8.5	0.56	10.8	1.31±0.26	10.8
Gamba组	L1(7)	35.3	64.1	29.9	159	9.2	0.61	10.2	1.6	15.8
	L2(8)	43.1	82.2	36.6	210	9.2	0.72	9.4	1.7	14.5
	N1(1)	78.2	139	50	319	12	0.97	15.7	2.8	24.2
	Tsi(23)	6.2	10.2	4.6	26.1	8.4	0.81	8.9	1.6	13.8
Dentale组	L1(2)	37.3	68.5	32	169.2	9.4	0.67	10.2	1.6	15.8
	L2(2)	54.7	106	46.2	273.2	10.9	0.67	10.9	1.9	6.9
	N1(6)	58.9	110.7	43.5	263	9.7	0.95	11.3	2	17.4
	Oba(43)	9.4	15.7	7.3	39.9	9.4	0.79	11.1	1.8	17.1
构造环境及层段		Zr	Sc	V	Co	Ti	La/Sc	Ti/Zr	Sc/Cr
大洋岛弧	杂砂岩^*	96±20	19.5±5.2	131±40	186.3	4800±1200	0.55±0.22	56.8±2.14	0.57±0.16
大陆岛弧	杂砂岩^*	229±27	14.8±1.7	89±13.7	122.7	3900±600	1.82±0.3	19.7±4.3	0.32±0.06
活动陆缘	杂砂岩^*	179±33	8.0±1.1	48±5.9	101.7	2600±200	4.55±0.8	15.3±2.4	0.30±0.02
被动陆缘	杂砂岩^*	298±80	6.0±1.4	31±9.9	52.4	2200±600	6.25±1.35	6.74±0.9	0.16±0.02
Gamba组	L1(7)	176	11.7	74	15.7	0.48	3.1	-	0.16
	L2(8)	299	15.4	125	17.8	0.83	2.9	-	0.18
	N1(1)	301	19.8	157	25.5	-	3.9	-	0.17
	Tsi(23)	100.2	1.9	17.6	-	-	4	-	0.61
Dentale组	L1(2)	186	12.4	76	17.8	-	3	-	0.17
	L2(2)	354	16.3	133	15.4	-	3.4	-	0.17
	N1(6)	334.5	17.4	133.7	19.4	-	3.4	-	0.18
	Oba(43)	115.7	2.2	30.8	-	-	4.8	-	0.79

构造环境及层段		La	Ce	Nd	∑REE	LREE/HREE	δEu	(La/Yb)_N	La/Y	La/Yb
大洋岛弧	杂砂岩^*	8.72±2.5	22.5±35.9	11.36±2.9	58±10	3.8±0.9	1.04±0.11	2.8±0.9	0.48±0.12	4.2±1.3
大陆岛弧	杂砂岩^*	24.4±2.3	50.5±4.3	20.8±1.6	146±20	7.7±1.7	0.79±0.13	7.5±2.5	1.02±0.07	7.5±2.5
活动陆缘	杂砂岩^*	33.0±4.5	72.7±9.8	25.4±3.4	186	9.1	0.6	8.5	1.33±0.09	8.5
被动陆缘	杂砂岩^*	44.5±5.8	71.9±11.5	29.0±5.03	210	8.5	0.56	10.8	1.31±0.26	10.8
Gamba组	L1(7)	35.3	64.1	29.9	159	9.2	0.61	10.2	1.6	15.8
	L2(8)	43.1	82.2	36.6	210	9.2	0.72	9.4	1.7	14.5
	N1(1)	78.2	139	50	319	12	0.97	15.7	2.8	24.2
	Tsi(23)	6.2	10.2	4.6	26.1	8.4	0.81	8.9	1.6	13.8
Dentale组	L1(2)	37.3	68.5	32	169.2	9.4	0.67	10.2	1.6	15.8
	L2(2)	54.7	106	46.2	273.2	10.9	0.67	10.9	1.9	6.9
	N1(6)	58.9	110.7	43.5	263	9.7	0.95	11.3	2	17.4
	Oba(43)	9.4	15.7	7.3	39.9	9.4	0.79	11.1	1.8	17.1
构造环境及层段		Zr	Sc	V	Co	Ti	La/Sc	Ti/Zr	Sc/Cr
大洋岛弧	杂砂岩^*	96±20	19.5±5.2	131±40	186.3	4800±1200	0.55±0.22	56.8±2.14	0.57±0.16
大陆岛弧	杂砂岩^*	229±27	14.8±1.7	89±13.7	122.7	3900±600	1.82±0.3	19.7±4.3	0.32±0.06
活动陆缘	杂砂岩^*	179±33	8.0±1.1	48±5.9	101.7	2600±200	4.55±0.8	15.3±2.4	0.30±0.02
被动陆缘	杂砂岩^*	298±80	6.0±1.4	31±9.9	52.4	2200±600	6.25±1.35	6.74±0.9	0.16±0.02
Gamba组	L1(7)	176	11.7	74	15.7	0.48	3.1	-	0.16
	L2(8)	299	15.4	125	17.8	0.83	2.9	-	0.18
	N1(1)	301	19.8	157	25.5	-	3.9	-	0.17
	Tsi(23)	100.2	1.9	17.6	-	-	4	-	0.61
Dentale组	L1(2)	186	12.4	76	17.8	-	3	-	0.17
	L2(2)	354	16.3	133	15.4	-	3.4	-	0.17
	N1(6)	334.5	17.4	133.7	19.4	-	3.4	-	0.18
	Oba(43)	115.7	2.2	30.8	-	-	4.8	-	0.79