Geochemical Characteristics Comparison and Tectonic Background Analysis of Siliceous Rocks from Qixia Formation and Gufeng Formation of Permian in Chaohu Area, Anhui Province

Abstract

Abstract:

Aiming to discuss the origin and sedimentary background of Permian chert in Yangtze region, we took the siliceous rocks as samples from Qixia Formation and Gufeng Formation in Chaohu area, which located in the northern margin of the Yangtze block. In this study, we collected previous research data of these two formations and systematically analyzed major, trace and rare elements data of siliceous rocks collected from the two formations.Test results of samples which we got in this study show that rare earth elements (REEs) pattern curves lean slightly to the left, with slight Ce negative anomaly and HREE relative enrichment, reflects the characteristics of the hydrothermal chert.The points pitched on the Al-Fe-Mn diagram of Qixia Formation and Gufeng Formation siliceous rocks indicate that most of the samples are high in Al. In this paper,we proposed that magma suffered the contamination of the Si-Al rich continental crust during the eruption,with high Al ratio. Combined with diagrams of sedimentary environments we came to a conclusion that cherts in Qixia Formation and Gufeng Formation were deposited at continental margin, continental margin-ocean basin, respectively. From Qixia Period to Gufeng Period, transgression scale became large, the depth of seawater became large, the area of ocean basin expanded, which made sedimentary environment different.The siliceous rocks sedimentation in both Qixia Formation and Gufeng Formation was closely related to continental margin chasmic activities.

Key words: siliceous rock, ocean basin, continental margin, hydrothermal sedimentation, Chaohu area

CLC Number:

P588.2

JIANATIGULI Wusiman, ZHOU Yaoqi, YAO Xu, XU Hanhua, FANG Xue. Geochemical Characteristics Comparison and Tectonic Background Analysis of Siliceous Rocks from Qixia Formation and Gufeng Formation of Permian in Chaohu Area, Anhui Province[J]. Geoscience, 2017, 31(04): 734-745.

Figures/Tables 14

References 35

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样品编号	SiO₂	Al₂O₃	TiO₂	Fe₂O₃	MnO	MgO	CaO	Na₂O	K₂O	P₂O₅
CH-qx-2	94.32	0.60	0.028	0.335	0.002 1	0.070	0.99	0.042	0.15	0.017 7
CH-qx-3	95.04	0.42	0.020	0.145	0.001 1	0.180	1.01	0.040	0.13	0.016 1
CH-qx-4	94.24	0.21	0.053	0.065	0.001 8	0.680	1.97	0.030	0.11	0.016 2
CH-qx-5	95.58	0.18	0.007	0.052	0.000 8	0.091	1.30	0.025	0.07	0.015 6
CH-qx-6	95.86	0.33	0.011	0.090	0.001 3	0.025	1.13	0.013	0.10	0.014 6
CH-qx-7	96.32	0.20	0.008	0.076	0.000 7	0.027	1.01	0.012	0.14	0.015 5
CH-qx-8	93.98	0.20	0.008	0.038	0.000 8	0.014	0.06	0.010	0.11	0.014 6
CH-qx-9	82.56	0.23	0.009	0.090	0.009 0	0.650	7.38	0.019	0.10	0.022 4
CH-gf-1	94.62	0.60	0.025	0.189	0.001 6	0.110	0.98	0.023	0.34	0.046 9
CH-gf-2	94.44	0.67	0.027	0.204	0.001 0	0.067	0.33	0.041	0.13	0.047 2
栖霞组均值	93.49	0.30	0.020	0.110	0.000 0	0.22	1.86	0.020	0.11	0.016 6
孤峰组均值	94.53	0.64	0.030	0.200	0.000 0	0.09	0.66	0.030	0.24	0.047 0

样品编号	SiO₂	Al₂O₃	TiO₂	Fe₂O₃	MnO	MgO	CaO	Na₂O	K₂O	P₂O₅
CH-qx-2	94.32	0.60	0.028	0.335	0.002 1	0.070	0.99	0.042	0.15	0.017 7
CH-qx-3	95.04	0.42	0.020	0.145	0.001 1	0.180	1.01	0.040	0.13	0.016 1
CH-qx-4	94.24	0.21	0.053	0.065	0.001 8	0.680	1.97	0.030	0.11	0.016 2
CH-qx-5	95.58	0.18	0.007	0.052	0.000 8	0.091	1.30	0.025	0.07	0.015 6
CH-qx-6	95.86	0.33	0.011	0.090	0.001 3	0.025	1.13	0.013	0.10	0.014 6
CH-qx-7	96.32	0.20	0.008	0.076	0.000 7	0.027	1.01	0.012	0.14	0.015 5
CH-qx-8	93.98	0.20	0.008	0.038	0.000 8	0.014	0.06	0.010	0.11	0.014 6
CH-qx-9	82.56	0.23	0.009	0.090	0.009 0	0.650	7.38	0.019	0.10	0.022 4
CH-gf-1	94.62	0.60	0.025	0.189	0.001 6	0.110	0.98	0.023	0.34	0.046 9
CH-gf-2	94.44	0.67	0.027	0.204	0.001 0	0.067	0.33	0.041	0.13	0.047 2
栖霞组均值	93.49	0.30	0.020	0.110	0.000 0	0.22	1.86	0.020	0.11	0.016 6
孤峰组均值	94.53	0.64	0.030	0.200	0.000 0	0.09	0.66	0.030	0.24	0.047 0

沉积环境	酸性	弱酸性	中性	弱碱性	碱性
MnO/Fe	<0.013	0.013~0.016	0.016~0.026	0.026~0.055	>0.055
pH值	<5	5~6	6~7.8	7.8~9	>9

沉积环境	酸性	弱酸性	中性	弱碱性	碱性
MnO/Fe	<0.013	0.013~0.016	0.016~0.026	0.026~0.055	>0.055
pH值	<5	5~6	6~7.8	7.8~9	>9

样品编号	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu
CH-qx-2	0.77	1.50	0.200	0.77	0.160	0.040	0.160	0.028	0.15	0.034	0.110	0.017	0.120	0.020
CH-qx-3	0.48	0.98	0.120	0.47	0.110	0.023	0.100	<0.02	0.10	0.016	0.055	0.0110	0.062	0.013
CH-qx-4	0.46	0.66	0.087	0.29	0.042	0.020	0.063	<0.02	0.07	0.013	0.048	<0.01	0.046	<0.01
CH-qx-5	0.26	0.43	0.070	0.22	0.055	0.018	0.065	<0.02	0.05	<0.01	0.045	<0.01	0.035	<0.01
CH-qx-6	0.30	0.51	0.074	0.29	0.029	0.020	0.063	<0.02	0.050	<0.01	0.038	<0.01	0.035	<0.01
CH-qx-7	0.43	0.82	0.100	0.31	0.060	0.015	0.045	<0.02	0.05	<0.01	0.038	<0.01	0.057	<0.01
CH-qx-8	0.07	0.16	<0.02	0.07	0.008	0.005	<0.02	<0.02	0.008	0.003	<0.02	<0.01	<0.03	<0.01
CH-qx-9	0.83	0.93	0.210	0.83	0.190	0.040	0.170	0.035	0.18	0.042	0.110	0.014	0.089	0.010
CH-gf-1	2.09	2.94	0.440	1.87	0.370	0.090	0.450	0.063	0.46	0.110	0.290	0.044	0.300	0.035
CH-gf-2	2.05	2.75	0.460	1.68	0.340	0.080	0.410	0.060	0.41	0.100	0.260	0.041	0.260	0.043
栖霞组均值	0.45	0.75	0.110	0.41	0.080	0.020	0.090	0.020	0.08	0.020	0.060	0.010	0.060	0.010
孤峰组均值	2.07	2.85	0.45	1.78	0.360	0.090	0.430	0.060	0.44	0.110	0.280	0.040	0.280	0.040