Geochemistry and Geochronology of West Shadegai Granites in Wulashan of Inner Mongolia and Its Geological Significance

Abstract

Abstract:

The West Shadegai granites in Wulashan of Inner Mongolia is located in Hadamengou molybdenum orefield,tectonically located in the west part of the northern margin of North China Craton,whose lithology is syenogranite. Geochemical characteristics show that the granite is characterized by high silicon (the mass fraction of SiO₂ is 74.08%-75.95%),rich potassium (K₂O/Na₂O=1.20-3.39),rich alkali (K₂O+Na₂O= 7.03%-8.46%),weakly peraluminous (mass fraction of Al₂O₃ is 11.22%-13.06%,A/CNK= 1.002-1.284).The Litman index belongs to the calc alkaline.The REEs are of enrichment of light rare earth elements,loss of heavy rare earth elements (LREE/HREE=19.84-27.83),and obvious loss of Eu (δEu=0.36-0.53).The enriched trace elements include Rb,Th,U,Pb,Zr,Hf,Sm; the loss elements include Ba,Ta,P,Ti;high field strength elements including Nb and Sr are slightly low,showing the characteristics of continental crust reformation type granite.The LA-ICP-MS ²⁰⁶Pb/²³⁸U weighted average age of 22 zircon samples from Shadegai pluton is (231±0.8) Ma,belonging to Middle Triassic. According to the contrast of the mineralization age and the diagenetic age,the diagenesis and mineralization both occurred in Late Triassic,and the mineralization age is slightly less than the diagenetic age,showing the pluton belongs to the product of extensional tectonic magmatic activity after Indosinian. According to the available age data,we concluded that significant tectono-magmatic molybdenite mineralization events had ever occurred in Indosinian.

Key words: West Shadegai granite, continental crust reformation type granite, molybdenum deposit, geochemistry, geochronology, Indosinian

CLC Number:

P588.12

DAI Chaocheng, HUANG Cheng, JIAO Zheng, WANG Xinliang. Geochemistry and Geochronology of West Shadegai Granites in Wulashan of Inner Mongolia and Its Geological Significance[J]. Geoscience, 2017, 31(04): 662-671.

Figures/Tables 10

References 29

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单位编号	样品编号	SiO₂	Al₂O₃		Fe₂O₃		MgO		CaO		Na₂O		K₂O		MnO		TiO₂		P₂O₅		FeO		CO₂		A/CNK
23240	TWB5GS	74.080	12.960		2.310		0.465		0.560		2.610		4.420		0.049		0.510		0.113		0.600		0.040		1.284
63555	GS D4629	74.130	11.220		4.260		0.344		0.606		1.810		6.140		0.026		0.198		0.050		1.300		0.040		1.046
63556	GS D2657	76.910	12.430		1.280		0.130		0.408		3.720		4.740		0.016		0.101		0.021		0.450		0.040		1.036
63557	GS D8058	75.160	13.060		1.820		0.312		0.691		3.740		4.600		0.037		0.213		0.062		0.630		0.080		1.054
63558	GS D1325	75.660	12.660		1.830		0.223		0.770		3.820		4.570		0.030		0.161		0.046		0.900		0.040		1.002
63559	GS D4640	75.950	12.150		2.500		0.202		0.221		2.460		5.910		0.036		0.183		0.026		1.330		0.130		1.120
平均值		75.315	12.413		2.333		0.279		0.543		3.027		5.063		0.032		0.228		0.053		0.868		0.062		1.090
单位编号	样品编号	SI		AR		σ43		σ25		R₁		R₂		F₁		F₂		F₃		A/MF		C/MF		DI
23240	TWB5GS	4.500		3.170		1.580		1.010		2 926		342.00		0.76		-1.02		-2.49		2.6		0.2		67.370
63555	GS D4629	2.510		5.100		2.030		1.290		2 711		302.00		0.76		-0.85		-2.38		1.38		0.14		74.070
63556	GS D2657	1.260		4.860		2.110		1.380		2 640		293.00		0.74		-1.03		-2.53		4.78		0.29		63.940
63557	GS D8058	2.820		4.080		2.170		1.380		2 525		344.00		0.73		-1.05		-2.53		3.26		0.31		60.990
63558	GS D1325	1.970		4.330		2.160		1.380		2 522		339.00		0.73		-1.06		-2.52		3.03		0.34		60.510
63559	GS D4640	1.630		5.180		2.130		1.370		2 670		269.00		0.76		-0.89		-2.44		2.17		0.07		72.400
平均值		2.448		4.453		2.030		1.302		2 666		314.833		0.747		-0.983		-2.482		2.870		0.225		66.547

单位编号	样品编号	SiO₂	Al₂O₃		Fe₂O₃		MgO		CaO		Na₂O		K₂O		MnO		TiO₂		P₂O₅		FeO		CO₂		A/CNK
23240	TWB5GS	74.080	12.960		2.310		0.465		0.560		2.610		4.420		0.049		0.510		0.113		0.600		0.040		1.284
63555	GS D4629	74.130	11.220		4.260		0.344		0.606		1.810		6.140		0.026		0.198		0.050		1.300		0.040		1.046
63556	GS D2657	76.910	12.430		1.280		0.130		0.408		3.720		4.740		0.016		0.101		0.021		0.450		0.040		1.036
63557	GS D8058	75.160	13.060		1.820		0.312		0.691		3.740		4.600		0.037		0.213		0.062		0.630		0.080		1.054
63558	GS D1325	75.660	12.660		1.830		0.223		0.770		3.820		4.570		0.030		0.161		0.046		0.900		0.040		1.002
63559	GS D4640	75.950	12.150		2.500		0.202		0.221		2.460		5.910		0.036		0.183		0.026		1.330		0.130		1.120
平均值		75.315	12.413		2.333		0.279		0.543		3.027		5.063		0.032		0.228		0.053		0.868		0.062		1.090
单位编号	样品编号	SI		AR		σ43		σ25		R₁		R₂		F₁		F₂		F₃		A/MF		C/MF		DI
23240	TWB5GS	4.500		3.170		1.580		1.010		2 926		342.00		0.76		-1.02		-2.49		2.6		0.2		67.370
63555	GS D4629	2.510		5.100		2.030		1.290		2 711		302.00		0.76		-0.85		-2.38		1.38		0.14		74.070
63556	GS D2657	1.260		4.860		2.110		1.380		2 640		293.00		0.74		-1.03		-2.53		4.78		0.29		63.940
63557	GS D8058	2.820		4.080		2.170		1.380		2 525		344.00		0.73		-1.05		-2.53		3.26		0.31		60.990
63558	GS D1325	1.970		4.330		2.160		1.380		2 522		339.00		0.73		-1.06		-2.52		3.03		0.34		60.510
63559	GS D4640	1.630		5.180		2.130		1.370		2 670		269.00		0.76		-0.89		-2.44		2.17		0.07		72.400
平均值		2.448		4.453		2.030		1.302		2 666		314.833		0.747		-0.983		-2.482		2.870		0.225		66.547

单位编号	样品编号	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	Y	ΣREE
23240	TWB5GS	98.3	156.0	14.80	47.20	6.06	0.91	5.06	0.63	3.47	0.66	2.22	0.40	3.13	0.55	21.80	339.39
63555	GSD4629	37.8	58.4	5.06	15.00	1.86	0.21	1.68	0.23	0.88	0.16	0.59	0.10	0.72	0.12	7.49	122.81
63556	GSD2657	19.5	25.0	2.10	5.61	0.69	0.13	0.75	0.10	0.47	0.10	0.36	0.08	0.68	0.13	3.59	55.70
63557	GSD8058	46.4	66.7	6.17	17.90	2.20	0.37	2.15	0.27	0.93	0.16	0.59	0.10	0.71	0.12	5.45	144.76
63558	GSD1325	46.7	63.1	5.80	16.30	2.00	0.32	1.94	0.25	0.98	0.18	0.67	0.12	0.94	0.16	6.24	139.47
63559	GSD4640	39.2	58.2	5.29	15.10	1.92	0.26	1.79	0.22	0.79	0.14	0.52	0.09	0.76	0.14	4.12	124.42
单位编号	样品编号	LREE	HREE	L/H	La_N/ Yb_N	δEu	δCe	Rb	Ba	Th	U	K	Ta	Nb	Sr	Zr	Hf
23240	TWB5GS	323.27	16.13	20.05	22.53	0.49	0.89	230	169	60.0	4.44	4.42	8.04	96.2	56.3	466	15.50
63555	GSD4629	118.33	4.48	26.41	37.45	0.36	0.90	395	650	20.4	23.60	6.14	2.13	38.6	52.9	126	3.58
63556	GSD2657	53.03	2.67	19.84	20.63	0.53	0.78	224	99	26.6	1.99	4.74	2.78	36.7	31.3	97	3.88
63557	GSD8058	139.74	5.02	27.83	46.68	0.51	0.84	208	621	29.2	4.80	4.60	2.30	29.2	165.0	139	4.32
63558	GSD1325	134.22	5.25	25.59	35.52	0.49	0.80	186	403	29.5	5.87	4.57	2.58	32.6	118.0	132	4.26
63559	GSD4640	119.97	4.45	26.96	36.90	0.42	0.86	377	540	32.3	6.23	5.91	3.09	49.4	76.6	146	5.06

单位编号	样品编号	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	Y	ΣREE
23240	TWB5GS	98.3	156.0	14.80	47.20	6.06	0.91	5.06	0.63	3.47	0.66	2.22	0.40	3.13	0.55	21.80	339.39
63555	GSD4629	37.8	58.4	5.06	15.00	1.86	0.21	1.68	0.23	0.88	0.16	0.59	0.10	0.72	0.12	7.49	122.81
63556	GSD2657	19.5	25.0	2.10	5.61	0.69	0.13	0.75	0.10	0.47	0.10	0.36	0.08	0.68	0.13	3.59	55.70
63557	GSD8058	46.4	66.7	6.17	17.90	2.20	0.37	2.15	0.27	0.93	0.16	0.59	0.10	0.71	0.12	5.45	144.76
63558	GSD1325	46.7	63.1	5.80	16.30	2.00	0.32	1.94	0.25	0.98	0.18	0.67	0.12	0.94	0.16	6.24	139.47
63559	GSD4640	39.2	58.2	5.29	15.10	1.92	0.26	1.79	0.22	0.79	0.14	0.52	0.09	0.76	0.14	4.12	124.42
单位编号	样品编号	LREE	HREE	L/H	La_N/ Yb_N	δEu	δCe	Rb	Ba	Th	U	K	Ta	Nb	Sr	Zr	Hf
23240	TWB5GS	323.27	16.13	20.05	22.53	0.49	0.89	230	169	60.0	4.44	4.42	8.04	96.2	56.3	466	15.50
63555	GSD4629	118.33	4.48	26.41	37.45	0.36	0.90	395	650	20.4	23.60	6.14	2.13	38.6	52.9	126	3.58
63556	GSD2657	53.03	2.67	19.84	20.63	0.53	0.78	224	99	26.6	1.99	4.74	2.78	36.7	31.3	97	3.88
63557	GSD8058	139.74	5.02	27.83	46.68	0.51	0.84	208	621	29.2	4.80	4.60	2.30	29.2	165.0	139	4.32
63558	GSD1325	134.22	5.25	25.59	35.52	0.49	0.80	186	403	29.5	5.87	4.57	2.58	32.6	118.0	132	4.26
63559	GSD4640	119.97	4.45	26.96	36.90	0.42	0.86	377	540	32.3	6.23	5.91	3.09	49.4	76.6	146	5.06

样品号(TWB5)	含量/10^-6		同位素比值				年龄/Ma
测点	Pb	U	²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²³⁵U	1σ	²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²³⁵U	1σ
1	37	1 029	0.036 5	0.000 4	0.253	0.003 1	231	2	230	3
2	52	1 402	0.036 7	0.000 3	0.253	0.002 8	232	2	229	3
3	35	931	0.036 2	0.000 3	0.285	0.012 5	229	2	255	11
4	66	1 678	0.036 4	0.000 3	0.286	0.004 3	231	2	255	4
5	45	1 265	0.036 4	0.000 3	0.256	0.002 9	230	2	232	3
6	47	1 267	0.036 5	0.000 3	0.311	0.003 3	231	2	275	3
7	81	2 123	0.036 5	0.000 3	0.327	0.004 5	231	2	288	4
8	75	1 793	0.036 3	0.000 3	0.309	0.004 4	230	2	274	4
9	40	1 111	0.036 4	0.000 3	0.255	0.003 2	231	2	231	3
10	68	1 742	0.036 3	0.000 3	0.260	0.006 7	230	2	235	6
11	62	1 579	0.036 4	0.000 3	0.303	0.008 3	231	2	269	7
12	35	941	0.036 5	0.000 3	0.252	0.005 0	231	2	229	5
13	36	881	0.036 7	0.000 3	0.283	0.005 6	232	2	253	5
14	21	616	0.036 2	0.000 4	0.256	0.009 2	230	2	232	8
15	72	1 789	0.036 6	0.000 3	0.289	0.004 3	232	2	258	4
16	32	890	0.036 4	0.000 3	0.256	0.003 7	231	2	231	3
17	68	1 502	0.036 3	0.000 4	0.295	0.005 5	230	2	263	5
18	55	1 207	0.036 3	0.000 4	0.324	0.012 6	230	2	285	11
19	90	1 752	0.037 0	0.000 3	0.293	0.005 3	234	2	261	5
20	100	1 767	0.036 7	0.000 3	0.296	0.003 2	232	2	264	3
21	55	1 406	0.036 3	0.000 3	0.258	0.003 2	230	2	233	3
22	26	743	0.031 4	0.000 3	0.352	0.005 0	199	2	306	4