Geochemical Characteristics of Cumulates in the Guomangcuo Ophiolites, Northern Tibet and Its Geological Significance

Abstract

Abstract:

The Guomangcuo ophiolite in the central Shiquanhe-Namco-Bomi ophiolitic mélange belt is composed of mantle peridotite,ultramafic-mafic cumulates,mafic lavas, dikes and siliceous rocks. Petrographic studies of the ultramafic cumulates show that the ultramafic cumulates has a well crystallization order. Trace elements analyses indicate that the ultramafic cumulates are enriched in HFSE,depleted in LILE,and that the compatible elements have a good change rule. The rare earth elements analyses also show a enriched LREE pattern with slight Eu anomaly,displaying that the rocks are formed from a enriched mantle source metasomatized by fluid in the slab subduction.Guomangcuo mafic rocks have both E-MORB and IAB affinity and are effected by the subduction fluids.We suggest that guomangcuo ophiolite likely developed in a back-arc basin,as a portion of Shiquanhe-Namco-Bomi ophiolitic mélange belt which is the Bangonghu-Nujiang Tethyan ocean back-arc basin.

Key words: Guomangcuo ophiolite, cumulate, geochemistry, enriched mantle source, back-arc basin

CLC Number:

P588.12

WANG Zhen, YE Peisheng, ZHANG Xujiao, YANG Xingchen, CHEN Yupeng, QI Jie, SHI Jianyue, SHENG Yuying. Geochemical Characteristics of Cumulates in the Guomangcuo Ophiolites, Northern Tibet and Its Geological Significance[J]. Geoscience, 2017, 31(03): 486-497.

Figures/Tables 11

References 30

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岩性	样品号	SiO₂	K₂O	Na₂O	CaO	MgO	MnO	FeO^T	Al₂O₃	TiO₂	P₂O₅	烧失量	总量
玄武岩	GMC-01	50.45	0.40	2.77	10.82	8.73	0.15	9.36	15.78	1.14	0.10	1.17	99.70
	GMC-03	51.43	0.53	2.72	10.87	9.14	0.14	8.69	15.66	0.91	0.08	1.57	100.17
	GMC-04	51.00	0.73	2.86	10.51	9.97	0.14	8.70	15.87	0.95	0.08	1.78	100.79
辉绿岩	GMC-05	52.80	0.45	4.01	8.07	8.17	0.17	9.91	14.19	1.36	0.15	1.96	99.28
	GMC-06	52.07	0.62	3.18	8.86	7.72	0.14	8.95	16.06	1.38	0.18	2.19	99.17
	GMC-07	51.10	0.58	2.77	10.37	8.57	0.16	8.67	15.96	1.16	0.13	2.33	99.47
纯橄岩	GMC-08	43.16	0.01	0.02	0.12	41.88	0.10	13.67	1.17	0.00	0.01	11.74	100.15
纯橄岩	GMC-09	45.65	0.02	0.03	0.23	41.07	0.13	12.25	1.17	0.01	0.01	12.10	100.57
方辉橄榄岩	GMC-10	41.94	0.01	0.02	0.18	42.25	0.10	13.38	1.62	0.01	0.01	11.96	99.52
	GMC-11	44.31	0.02	0.03	0.18	40.53	0.09	13.94	1.15	0.04	0.01	11.88	100.30
	GMC-16	45.15	0.01	0.03	0.24	46.09	0.10	7.47	1.23	0.00	0.01	15.85	100.34
二辉橄榄岩	GMC-12	46.44	0.01	0.04	2.89	37.59	0.11	11.69	1.24	0.01	0.01	11.15	100.03
	GMC-13	48.97	0.02	0.08	7.68	32.00	0.12	9.83	1.43	0.00	0.01	9.38	100.14
	GMC-14	47.88	0.02	0.06	6.29	33.59	0.11	10.33	1.43	0.00	0.01	9.50	99.72
	GMC-15	47.03	0.02	0.08	7.44	33.34	0.17	10.15	2.65	0.05	0.01	8.40	100.95
单斜辉石岩	GMC-17	53.09	0.02	0.17	19.63	19.83	0.13	5.19	2.48	0.01	0.01	0.82	100.56
	GMC-18	52.29	0.01	0.15	19.15	19.60	0.14	5.39	2.71	0.00	0.01	2.34	99.47
	GMC-19	47.99	0.01	0.11	10.23	31.66	0.13	8.55	1.84	0.04	0.01	6.36	100.58
	GMC-20	52.47	0.03	0.16	18.85	19.70	0.13	5.28	2.59	0.03	0.01	0.67	99.25
	GMC-21	52.59	0.01	0.17	19.41	19.20	0.13	5.46	2.61	0.01	0.01	0.92	99.59

岩性	样品号	SiO₂	K₂O	Na₂O	CaO	MgO	MnO	FeO^T	Al₂O₃	TiO₂	P₂O₅	烧失量	总量
玄武岩	GMC-01	50.45	0.40	2.77	10.82	8.73	0.15	9.36	15.78	1.14	0.10	1.17	99.70
	GMC-03	51.43	0.53	2.72	10.87	9.14	0.14	8.69	15.66	0.91	0.08	1.57	100.17
	GMC-04	51.00	0.73	2.86	10.51	9.97	0.14	8.70	15.87	0.95	0.08	1.78	100.79
辉绿岩	GMC-05	52.80	0.45	4.01	8.07	8.17	0.17	9.91	14.19	1.36	0.15	1.96	99.28
	GMC-06	52.07	0.62	3.18	8.86	7.72	0.14	8.95	16.06	1.38	0.18	2.19	99.17
	GMC-07	51.10	0.58	2.77	10.37	8.57	0.16	8.67	15.96	1.16	0.13	2.33	99.47
纯橄岩	GMC-08	43.16	0.01	0.02	0.12	41.88	0.10	13.67	1.17	0.00	0.01	11.74	100.15
纯橄岩	GMC-09	45.65	0.02	0.03	0.23	41.07	0.13	12.25	1.17	0.01	0.01	12.10	100.57
方辉橄榄岩	GMC-10	41.94	0.01	0.02	0.18	42.25	0.10	13.38	1.62	0.01	0.01	11.96	99.52
	GMC-11	44.31	0.02	0.03	0.18	40.53	0.09	13.94	1.15	0.04	0.01	11.88	100.30
	GMC-16	45.15	0.01	0.03	0.24	46.09	0.10	7.47	1.23	0.00	0.01	15.85	100.34
二辉橄榄岩	GMC-12	46.44	0.01	0.04	2.89	37.59	0.11	11.69	1.24	0.01	0.01	11.15	100.03
	GMC-13	48.97	0.02	0.08	7.68	32.00	0.12	9.83	1.43	0.00	0.01	9.38	100.14
	GMC-14	47.88	0.02	0.06	6.29	33.59	0.11	10.33	1.43	0.00	0.01	9.50	99.72
	GMC-15	47.03	0.02	0.08	7.44	33.34	0.17	10.15	2.65	0.05	0.01	8.40	100.95
单斜辉石岩	GMC-17	53.09	0.02	0.17	19.63	19.83	0.13	5.19	2.48	0.01	0.01	0.82	100.56
	GMC-18	52.29	0.01	0.15	19.15	19.60	0.14	5.39	2.71	0.00	0.01	2.34	99.47
	GMC-19	47.99	0.01	0.11	10.23	31.66	0.13	8.55	1.84	0.04	0.01	6.36	100.58
	GMC-20	52.47	0.03	0.16	18.85	19.70	0.13	5.28	2.59	0.03	0.01	0.67	99.25
	GMC-21	52.59	0.01	0.17	19.41	19.20	0.13	5.46	2.61	0.01	0.01	0.92	99.59

岩性	样品号	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu
玄武岩	GMC-01	4.76	10.79	1.69	9.10	2.87	1.19	2.95	0.66	4.63	0.99	2.76	0.48	3.13	0.49
	GMC-03	4.17	9.62	1.54	8.44	2.73	1.15	2.76	0.63	4.40	0.91	2.53	0.43	2.86	0.45
	GMC-04	4.87	10.46	1.62	8.62	2.73	1.15	2.84	0.64	4.41	0.93	2.57	0.44	2.91	0.45
辉绿岩	GMC-05	6.36	12.84	1.91	9.64	2.77	0.95	2.67	0.59	3.97	0.85	2.37	0.40	2.53	0.41
	GMC-06	9.25	17.81	2.64	12.97	3.64	1.21	3.40	0.77	5.21	1.10	3.08	0.52	3.36	0.52
	GMC-07	7.89	15.52	2.28	11.10	3.05	1.13	2.80	0.61	4.00	0.83	2.27	0.38	2.43	0.39
纯橄岩	GMC-08	0.07	0.17	0.01	0.06	0.01	0.01	0.02	0.00	0.03	0.01	0.02	0.00	0.03	0.01
纯橄岩	GMC-09	0.10	0.21	0.02	0.10	0.03	0.02	0.03	0.01	0.07	0.02	0.05	0.01	0.06	0.01
方辉橄榄岩	GMC-10	0.20	0.37	0.04	0.15	0.04	0.02	0.04	0.01	0.08	0.02	0.06	0.01	0.08	0.01
	GMC-11	0.54	0.75	0.07	0.24	0.05	0.02	0.05	0.01	0.06	0.02	0.05	0.01	0.06	0.01
	GMC-16	0.69	1.23	0.17	0.88	0.22	0.07	0.20	0.05	0.29	0.06	0.17	0.03	0.18	0.03
二辉橄榄岩	GMC-12	0.32	0.57	0.06	0.30	0.11	0.04	0.11	0.03	0.25	0.05	0.17	0.03	0.19	0.03
	GMC-13	1.43	2.11	0.22	0.91	0.20	0.07	0.23	0.05	0.32	0.07	0.22	0.04	0.23	0.04
	GMC-14	2.15	3.37	0.36	1.41	0.30	0.08	0.31	0.06	0.42	0.09	0.26	0.04	0.30	0.05
	GMC-15	3.75	5.89	0.57	2.20	0.46	0.13	0.49	0.09	0.58	0.13	0.34	0.06	0.39	0.06
单斜辉石岩	GMC-17	0.21	0.47	0.06	0.43	0.18	0.08	0.22	0.06	0.46	0.11	0.30	0.05	0.34	0.06
	GMC-18	0.25	0.52	0.08	0.52	0.25	0.10	0.28	0.08	0.62	0.14	0.40	0.07	0.45	0.08
	GMC-19	2.45	3.60	0.39	1.62	0.37	0.10	0.39	0.08	0.56	0.12	0.35	0.06	0.39	0.06
	GMC-20	0.40	0.84	0.12	0.72	0.32	0.13	0.38	0.10	0.83	0.19	0.55	0.10	0.62	0.11
	GMC-21	2.67	4.61	0.48	2.00	0.59	0.20	0.64	0.15	1.11	0.25	0.72	0.12	0.83	0.13

岩性	样品号	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu
玄武岩	GMC-01	4.76	10.79	1.69	9.10	2.87	1.19	2.95	0.66	4.63	0.99	2.76	0.48	3.13	0.49
	GMC-03	4.17	9.62	1.54	8.44	2.73	1.15	2.76	0.63	4.40	0.91	2.53	0.43	2.86	0.45
	GMC-04	4.87	10.46	1.62	8.62	2.73	1.15	2.84	0.64	4.41	0.93	2.57	0.44	2.91	0.45
辉绿岩	GMC-05	6.36	12.84	1.91	9.64	2.77	0.95	2.67	0.59	3.97	0.85	2.37	0.40	2.53	0.41
	GMC-06	9.25	17.81	2.64	12.97	3.64	1.21	3.40	0.77	5.21	1.10	3.08	0.52	3.36	0.52
	GMC-07	7.89	15.52	2.28	11.10	3.05	1.13	2.80	0.61	4.00	0.83	2.27	0.38	2.43	0.39
纯橄岩	GMC-08	0.07	0.17	0.01	0.06	0.01	0.01	0.02	0.00	0.03	0.01	0.02	0.00	0.03	0.01
纯橄岩	GMC-09	0.10	0.21	0.02	0.10	0.03	0.02	0.03	0.01	0.07	0.02	0.05	0.01	0.06	0.01
方辉橄榄岩	GMC-10	0.20	0.37	0.04	0.15	0.04	0.02	0.04	0.01	0.08	0.02	0.06	0.01	0.08	0.01
	GMC-11	0.54	0.75	0.07	0.24	0.05	0.02	0.05	0.01	0.06	0.02	0.05	0.01	0.06	0.01
	GMC-16	0.69	1.23	0.17	0.88	0.22	0.07	0.20	0.05	0.29	0.06	0.17	0.03	0.18	0.03
二辉橄榄岩	GMC-12	0.32	0.57	0.06	0.30	0.11	0.04	0.11	0.03	0.25	0.05	0.17	0.03	0.19	0.03
	GMC-13	1.43	2.11	0.22	0.91	0.20	0.07	0.23	0.05	0.32	0.07	0.22	0.04	0.23	0.04
	GMC-14	2.15	3.37	0.36	1.41	0.30	0.08	0.31	0.06	0.42	0.09	0.26	0.04	0.30	0.05
	GMC-15	3.75	5.89	0.57	2.20	0.46	0.13	0.49	0.09	0.58	0.13	0.34	0.06	0.39	0.06
单斜辉石岩	GMC-17	0.21	0.47	0.06	0.43	0.18	0.08	0.22	0.06	0.46	0.11	0.30	0.05	0.34	0.06
	GMC-18	0.25	0.52	0.08	0.52	0.25	0.10	0.28	0.08	0.62	0.14	0.40	0.07	0.45	0.08
	GMC-19	2.45	3.60	0.39	1.62	0.37	0.10	0.39	0.08	0.56	0.12	0.35	0.06	0.39	0.06
	GMC-20	0.40	0.84	0.12	0.72	0.32	0.13	0.38	0.10	0.83	0.19	0.55	0.10	0.62	0.11
	GMC-21	2.67	4.61	0.48	2.00	0.59	0.20	0.64	0.15	1.11	0.25	0.72	0.12	0.83	0.13

岩性	样品号	Rb	Ba	Th	U	Nb	Ta	Pb	Sr	Zr	Hf	Y	Ni	Cr	Co	V
玄武岩	GMC-01	4.64	63.00	1.50	0.22	9.30	0.42	14.60	177.00	82.00	4.76	19.70	80.60	224.00	37.69	214.50
	GMC-03	6.59	74.00	0.63	0.11	7.30	0.49	13.30	171.00	67.00	4.01	18.40	92.90	238.00	39.92	223.30
	GMC-04	13.44	67.00	0.90	0.16	5.80	0.62	13.70	164.00	59.00	4.41	16.60	110.20	297.00	44.34	232.20
辉绿岩	GMC-05	5.66	82.00	1.72	0.16	11.20	0.52	12.50	125.00	100.00	3.33	22.60	79.80	170.00	27.78	159.40
	GMC-06	6.74	118.00	1.48	0.20	15.40	0.49	14.30	262.00	114.00	4.58	22.30	100.00	224.00	33.42	204.80
	GMC-07	10.77	106.00	1.06	0.45	11.60	0.40	11.20	264.00	96.00	3.78	17.90	97.20	246.00	33.34	190.50
纯橄岩	GMC-08	0.28	1.00	0.21	0.05	0.80	0.00	0.50	6.00	14.00	0.22	0.10	1 769.30	1 743.00	87.13	150.50
纯橄岩	GMC-09	0.35	1.00	0.15	0.13	0.80	0.00	0.20	10.00	13.00	0.16	0.10	1 331.10	754.00	100.40	135.50
方辉橄榄岩	GMC-10	0.52	3.00	0.13	0.12	0.80	0.00	0.20	10.00	13.00	0.12	0.10	1 424.20	382.00	114.80	65.43
	GMC-11	0.88	1.00	0.17	0.10	0.80	0.00	0.20	9.00	17.00	0.15	0.10	1 531.50	223.00	121.20	52.47
	GMC-16	1.37	6.00	0.41	0.05	0.80	0.02	0.20	6.00	13.00	1.13	0.10	2 295.20	3 241.00	70.50	206.90
二辉橄榄岩	GMC-12	0.65	15.00	0.14	0.13	0.80	0.01	0.20	11.00	19.00	0.16	0.10	1 163.20	1 470.00	104.60	126.00
	GMC-13	3.10	13.00	0.39	0.18	0.80	0.01	3.20	13.00	16.00	0.13	0.80	915.40	1 750.00	82.34	224.30
	GMC-14	5.45	2.00	0.65	0.25	0.80	0.01	1.80	11.00	18.00	0.19	0.10	950.80	1 660.00	93.74	233.20
	GMC-15	9.68	1.00	1.31	0.17	0.80	0.01	2.90	9.00	13.00	0.41	0.60	853.50	2 126.00	102.70	279.00
单斜辉石岩	GMC-17	0.73	15.00	0.25	0.11	4.60	0.01	17.50	14.00	16.00	0.33	5.30	305.20	3 066.00	47.59	13.45
	GMC-18	0.51	12.00	0.13	0.11	3.90	0.00	15.20	13.00	15.00	0.29	5.10	407.70	4 138.00	43.37	25.90
	GMC-19	5.41	11.00	0.63	0.11	0.80	0.01	4.90	8.00	19.00	0.24	1.50	832.80	2 827.00	94.74	35.50
	GMC-20	1.15	16.00	0.28	0.07	4.60	0.01	16.50	12.00	21.00	0.49	5.20	325.50	3 593.00	68.32	30.51
	GMC-21	10.52	16.00	1.04	0.12	4.00	0.01	15.00	13.00	15.00	0.59	5.90	307.10	3 218.00	63.02	30.25