Paleoenvironmental Reconstruction and Organic Matter Enrichment of Middle Permian Black Shale: Insights From the Gufeng Formation, Enshi Area, Western Hubei

doi:10.19657/j.geoscience.1000-8527.2024.071

Abstract

Abstract:

A series of black rocks dominated by basin facies developed in the Middle Permian Gufeng Formation in the Enshi area, Western Hubei Province.This formation was recently identified for shale gas development and exploration; however, little is known about the sedimentary paleoenvironment and the mechanisms of orga-nic matter enrichment in the black rock series.In this study, we focus primarily on two sections of the Gufeng Formation, Tianfengping and Yutangba, located in the Enshi area, Western Hubei.Our aim is to elucidate the paleoenvironment during the sedimentary phase of the Gufeng Formation shale and to identify the key factors governing organic matter accumulation in this area.A comprehensive suite of analytical techniques was used in this study, including petrography, mineralogy, total organic carbon (TOC) quantification, and elemental geochemistry.The results reveal that the Gufeng Formation shale predominantly consists of siliceous shale facies, with a notable TOC content ranging from 5.8% to 41.6%.Quartz (81.5% on average) and clay minerals (12.6% on average) constitute the bulk of the mineral assemblages, with minor contributions from feldspar, pyrite, and carbonate minerals.The Chemical Alteration Index (CIA) suggests that the sedimentary environment of the Gufeng Formation shale was primarily characterized by hot and humid climate.The V/(V+Ni) and U/Th ratios indicate anoxic to sulfidic conditions in the bottom waters.The biogenic silicon (Si_bio), Cu/Al,Ni/Al values indicate higher primary productivity during the depositional phase.The weak correlation between TOC and U/Th, Al, Ti/Al suggests that bottom water anoxic sulfidic conditions and terrigenous detrital input have a limited influence on organic matter enrichment in black shales of the Gufeng Formation.Conversely, the positive correlation with Ni/Al suggests the primary productivity is a pivotal factor driving organic matter enrichment.The sedimentary environment of the Gufeng Formation shale is characterized by deep-water anoxia, a hot and humid climate, and high primary productivity.We therefore established a depositional environmental model for deep-water intraplatform basins, constrained by redox conditions, paleo-productivity, and a hot-humid paleoclimate.

Key words: Enshi area of Western Hubei, Gufeng Formation of the Middle Permian, black shale, lithofacies, sedimentary environment, organic matter enrichment

CLC Number:

P618.1

LIU Bei, GAO Xianzhi, LI Feng, GONG Zhiyu, LUO Fan, DU Xiaofeng. Paleoenvironmental Reconstruction and Organic Matter Enrichment of Middle Permian Black Shale: Insights From the Gufeng Formation, Enshi Area, Western Hubei[J]. Geoscience, 2024, 38(06): 1484-1497.

Figures/Tables 14

References 44

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样品编号	TOC(%)	SiO₂(%)	Al₂O₃(%)	Fe₂O₃(%)	CaO(%)	MgO(%)	Na₂O(%)	K₂O(%)	TiO₂(%)	P₂O₅(%)
T-7	11.53	73.11	2.23	9.17	0.07	0.14	0.08	0.36	0.16	0.62
T-6	19.55	80.25	1.60	1.38	0.09	0.11	0.06	0.26	0.07	0.12
T-5	24.66	75.41	3.63	0.04	0.08	0.35	0.08	0.79	0.18	0.07
T-4	13.64	74.58	8.03	0.38	0.11	0.69	0.10	1.80	0.42	0.06
T-3	5.79	90.18	2.32	0.55	0.09	0.16	0.07	0.31	0.08	0.12
T-2	10.65	87.58	3.07	0.37	0.12	0.26	0.08	0.51	0.13	0.16
T-1	6.34	87.72	2.79	0.43	0.38	0.29	0.09	0.49	0.11	0.18
Y-6	10.63	84.69	2.42	0.13	0.10	0.18	0.04	0.38	0.14	0.16
Y-5	7.49	80.66	2.70	0.07	0.12	0.32	0.03	0.48	0.14	0.03
Y-4	41.59	78.03	1.59	0.11	0.07	0.24	0.02	0.27	0.05	0.08
Y-3	31.09	76.88	3.15	0.14	0.58	0.40	0.05	0.62	0.12	0.55
Y-2	6.07	87.00	1.80	0.14	0.38	0.13	0.04	0.34	0.06	0.46
Y-1	9.36	85.37	2.55	0.08	0.26	0.29	0.05	0.43	0.09	0.25

样品编号	TOC(%)	SiO₂(%)	Al₂O₃(%)	Fe₂O₃(%)	CaO(%)	MgO(%)	Na₂O(%)	K₂O(%)	TiO₂(%)	P₂O₅(%)
T-7	11.53	73.11	2.23	9.17	0.07	0.14	0.08	0.36	0.16	0.62
T-6	19.55	80.25	1.60	1.38	0.09	0.11	0.06	0.26	0.07	0.12
T-5	24.66	75.41	3.63	0.04	0.08	0.35	0.08	0.79	0.18	0.07
T-4	13.64	74.58	8.03	0.38	0.11	0.69	0.10	1.80	0.42	0.06
T-3	5.79	90.18	2.32	0.55	0.09	0.16	0.07	0.31	0.08	0.12
T-2	10.65	87.58	3.07	0.37	0.12	0.26	0.08	0.51	0.13	0.16
T-1	6.34	87.72	2.79	0.43	0.38	0.29	0.09	0.49	0.11	0.18
Y-6	10.63	84.69	2.42	0.13	0.10	0.18	0.04	0.38	0.14	0.16
Y-5	7.49	80.66	2.70	0.07	0.12	0.32	0.03	0.48	0.14	0.03
Y-4	41.59	78.03	1.59	0.11	0.07	0.24	0.02	0.27	0.05	0.08
Y-3	31.09	76.88	3.15	0.14	0.58	0.40	0.05	0.62	0.12	0.55
Y-2	6.07	87.00	1.80	0.14	0.38	0.13	0.04	0.34	0.06	0.46
Y-1	9.36	85.37	2.55	0.08	0.26	0.29	0.05	0.43	0.09	0.25

样品编号	Cr (10^-6)	Sr (10^-6)	V (10^-6)	Ni (10^-6)	Co (10^-6)	Ba (10^-6)	Cu (10^-6)	U (10^-6)	Mo (10^-6)	Mn (10^-6)	Rb (10^-6)	Th (10^-6)	Ga (10^-6)
T-1	574	60	204	31	0.65	62	19	13.6	13	18.11	16.31	1.51	2.95
T-2	874	127	1194	32	0.74	64	68	19.6	76	27.86	17.73	1.70	3.42
T-3	607	165	1506	38	0.52	50	42	11.7	120	18.28	11.01	0.85	2.57
T-4	1334	114	2157	64	0.93	161	16	18.2	52	20.72	62.56	5.32	10.90
T-5	1192	217	1546	173	0.65	106	21	9.94	21	23.22	27.30	2.05	5.67
T-6	519	45	1487	108	0.59	37	52	8.7	23	32.68	9.472	0.75	3.15
T-7	433	156	1283	40	1.18	90	74	11.3	108	43.70	12.86	1.65	4.05
Y-1	413	70	413	98	0.74	39	68	18.2	106	16.69	12.60	2.43	2.68
Y-2	366	75	366	126	0.66	40	14	16.4	48	22.39	10.37	0.68	2.00
Y-3	684	133	684	306	1.33	53	88	98.6	219	26.6	22.03	1.57	3.89
Y-4	271	25	271	240	0.19	41	310	17.8	376	16.69	11.28	1.13	2.55
Y-5	146	48	146	128	0.25	80	30	18.9	472	18.70	19.74	1.96	3.81
Y-6	474	125	474	225	0.56	66	57	14.1	283	26.6	15.34	1.54	4.53

样品编号	Cr (10^-6)	Sr (10^-6)	V (10^-6)	Ni (10^-6)	Co (10^-6)	Ba (10^-6)	Cu (10^-6)	U (10^-6)	Mo (10^-6)	Mn (10^-6)	Rb (10^-6)	Th (10^-6)	Ga (10^-6)
T-1	574	60	204	31	0.65	62	19	13.6	13	18.11	16.31	1.51	2.95
T-2	874	127	1194	32	0.74	64	68	19.6	76	27.86	17.73	1.70	3.42
T-3	607	165	1506	38	0.52	50	42	11.7	120	18.28	11.01	0.85	2.57
T-4	1334	114	2157	64	0.93	161	16	18.2	52	20.72	62.56	5.32	10.90
T-5	1192	217	1546	173	0.65	106	21	9.94	21	23.22	27.30	2.05	5.67
T-6	519	45	1487	108	0.59	37	52	8.7	23	32.68	9.472	0.75	3.15
T-7	433	156	1283	40	1.18	90	74	11.3	108	43.70	12.86	1.65	4.05
Y-1	413	70	413	98	0.74	39	68	18.2	106	16.69	12.60	2.43	2.68
Y-2	366	75	366	126	0.66	40	14	16.4	48	22.39	10.37	0.68	2.00
Y-3	684	133	684	306	1.33	53	88	98.6	219	26.6	22.03	1.57	3.89
Y-4	271	25	271	240	0.19	41	310	17.8	376	16.69	11.28	1.13	2.55
Y-5	146	48	146	128	0.25	80	30	18.9	472	18.70	19.74	1.96	3.81
Y-6	474	125	474	225	0.56	66	57	14.1	283	26.6	15.34	1.54	4.53

样品编号	V/ (V+Ni)	U/ Th	Cr_ef	Sr_ef	V_ef	Ni_ef	Ba_ef	Cu_ef	Mo_ef
T-1	0.869	8.97	19.96	0.49	5.5	2.03	0.33	2.19	38.17	22.85	0.42	0.41	0.50	13.01	20.79	0.12	36.37	1.47	0.046
T-2	0.974	11.54	27.62	0.95	29.25	1.91	0.31	7.13	197.2	30.04	0.41	0.42	0.53	41.91	19.39	0.21	35.84	1.62	0.046
T-3	0.975	13.7	19.18	1.64	48.83	3.00	0.32	5.83	414.3	23.65	0.34	0.28	0.52	34.01	31.19	0.10	38.28	1.23	0.041
T-4	0.971	3.43	16.09	0.33	20.18	1.46	0.29	0.64	52.01	10.65	0.56	0.50	0.64	3.69	15.09	0.19	21.62	4.25	0.059
T-5	0.975	4.85	31.83	1.37	32.04	8.72	0.43	1.86	46.92	12.87	0.54	0.42	0.74	10.85	90.32	0.15	29.24	1.92	0.055
T-6	0.974	11.56	31.48	0.65	69.96	12.36	0.34	10.47	117	25.59	0.43	0.35	0.93	61.83	127.30	0.19	34.83	0.85	0.051
T-7	0.869	6.85	18.78	1.60	43.15	3.27	0.59	10.65	387.7	23.73	0.41	0.55	0.86	62.78	33.66	0.51	30.45	1.18	0.079
Y-1	0.823	7.49	15.69	0.63	12.17	7.02	0.22	8.58	282.4	48.34	0.35	0.72	0.50	42.00	72.60	0.12	35.65	1.35	0.038
Y-2	0.799	23.90	19.73	0.96	15.31	12.82	0.33	2.51	214.3	42.74	0.41	0.28	0.53	31.95	132.60	0.15	37.65	0.95	0.040
Y-3	0.896	62.70	21.07	0.97	16.34	17.77	0.25	9.00	557.7	147.20	0.50	0.37	0.58	186.00	183.40	0.35	30.71	1.67	0.042
Y-4	0.921	15.76	16.53	0.36	12.85	27.66	0.38	62.89	1898	52.76	0.51	0.54	0.76	104.20	285.60	0.03	33.81	0.84	0.037
Y-5	0.925	9.65	5.24	0.41	4.06	8.66	0.43	3.57	1399	32.81	0.52	0.55	0.67	10.07	89.27	0.05	33.21	1.43	0.057
Y-6	0.865	9.16	18.97	1.19	14.72	16.99	0.40	7.57	326.5	62.45	0.46	0.48	0.89	53.39	175.60	0.15	35.55	1.28	0.064