Discovery of the Early Indosinian Granite in Lujing Area, Hunan and Jiangxi Border and Its Geological Significance

doi:10.19657/j.geoscience.1000-8527.2018.05.01

Abstract

Abstract:

Indosinian granites are widely distributed in Southern China. Previous studies indicate that the Indosinian granites mainly concentrated in the Middle-Late Triassic are attributed to post-collisional granite type. In this paper, we reported a Jiaoyelong concealed granite from Lujing area, the border of the Hunan and Jiangxi provinces. The results show that this granite with medium-coarse grained granitic texture and muscovite is chara-cterized by high contents of silicon (SiO₂=73.97%-76.92%), aluminum (Al₂O₃=12.56%-13.86%), potassium (K₂O=4.02%-5.13%), and K₂O>Na₂O, and belongs to high potassium calcalkaline series. The A/CNK ranges from 1.17 to 1.30,suggesting a peraluminous series. It is rich in large ion lithophile elements (Rb, K, etc.) and high field intensity elements (Th, U, Ta, Nb, Zr, Hf, etc). The contents of U range from 3.24 × 10^-6 to 15.40×10^-6, with the average content of 8.31 × 10^-6. The ratio of Th/U is 1.21-1.98, indicating a rich uranium pluton property. This granite enriched in LREE has a relatively high fractionation between LREE and HREE. LA-ICP-MS zircon U-Pb dating of the granite yields a mean age of (247±2.2) Ma, belonging to the early Indosinian intrusion. Furthermore, the aluminum saturation index and Rb/30-Hf-3Ta diagram show that the pluton formed in the collisional continental margin tectonic background, suggesting that a tectonic transition from compression to extension took place in Southern China during the Early-Middle Triassic.

Key words: medium-coarse grained granite, zircon age, syn-collision, tectonic transformation, Hunan-Jiangxi border

CLC Number:

P588.121

ZHANG Wanliang, GAO Mengqi, LÜ Chuan, HUANG Chao, HUANG Di, XIE Zhicong. Discovery of the Early Indosinian Granite in Lujing Area, Hunan and Jiangxi Border and Its Geological Significance[J]. Geoscience, 2018, 32(05): 863-873.

Figures/Tables 16

References 27

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样号	取样位置	SiO₂	Al₂O₃	Fe₂O₃	FeO	CaO	MgO	K₂O	Na₂O	TiO₂	P₂O₅	MnO	烧失量	总计
LY16-17	ZK91-1,488.30 m	74.10	13.51	1.12	0.540	0.949	0.548	5.13	1.88	0.187	0.222	0.057	1.45	100.15
LY16-18	ZK67-1,312.70 m	76.92	12.56	0.740	0.290	0.555	0.151	4.02	3.25	0.074	0.282	0.067	0.67	99.75
JD5-4	ZK83-1,424.00 m	73.97	13.86	0.654	0.767	0.643	0.324	4.93	3.27	0.155	0.287	0.053	0.867	99.92
JD5-3	ZK75-2,260.90 m	75.31	13.64	0.680	0.395	0.584	0.223	4.26	3.35	0.094	0.242	0.056	1.22	100.31
4样平均值		75.08	13.39	0.80	0.50	0.68	0.31	4.59	2.94	0.13	0.26	0.06	1.05	100.03
分析检出限		18.98	0.21	0.09	0.50	0.07	0.08	0.01	0.06	0.01	0.004	0.002	0.10

样号	取样位置	SiO₂	Al₂O₃	Fe₂O₃	FeO	CaO	MgO	K₂O	Na₂O	TiO₂	P₂O₅	MnO	烧失量	总计
LY16-17	ZK91-1,488.30 m	74.10	13.51	1.12	0.540	0.949	0.548	5.13	1.88	0.187	0.222	0.057	1.45	100.15
LY16-18	ZK67-1,312.70 m	76.92	12.56	0.740	0.290	0.555	0.151	4.02	3.25	0.074	0.282	0.067	0.67	99.75
JD5-4	ZK83-1,424.00 m	73.97	13.86	0.654	0.767	0.643	0.324	4.93	3.27	0.155	0.287	0.053	0.867	99.92
JD5-3	ZK75-2,260.90 m	75.31	13.64	0.680	0.395	0.584	0.223	4.26	3.35	0.094	0.242	0.056	1.22	100.31
4样平均值		75.08	13.39	0.80	0.50	0.68	0.31	4.59	2.94	0.13	0.26	0.06	1.05	100.03
分析检出限		18.98	0.21	0.09	0.50	0.07	0.08	0.01	0.06	0.01	0.004	0.002	0.10

样号	取样位置	Ni	Co	Rb	Sr	Ba	Nb	Ta	U	Th	Zr	Hf	Ga
LY16-17	ZK91-1,488.30 m	2.50	2.12	400	40.6	150	23.0	3.64	8.83	16.9	84.2	3.78	19.4
LY16-18	ZK67-1,312.70 m	1.88	0.99	460	16.3	33.4	27.1	5.56	3.24	6.42	36.5	2.25	18.7
JD5-4	ZK83-1,424.00 m	1.79	1.41	344	40.3	142	22.1	3.28	15.4	18.7	83.5	3.42	17.1
JD5-3	ZK75-2,260.90 m	1.68	1.38	438	23.0	35.4	36.1	5.87	5.76	10.2	39.9	2.78	21.4
4样平均值		1.96	1.48	410.50	30.05	90.20	27.08	4.59	8.31	13.06	61.03	3.06	19.15
分析检出限		1.00	0.20	1.00	0.20	0.50	1.00	2.90	0.003	0.80	1.20	0.50	0.20

样号	取样位置	Ni	Co	Rb	Sr	Ba	Nb	Ta	U	Th	Zr	Hf	Ga
LY16-17	ZK91-1,488.30 m	2.50	2.12	400	40.6	150	23.0	3.64	8.83	16.9	84.2	3.78	19.4
LY16-18	ZK67-1,312.70 m	1.88	0.99	460	16.3	33.4	27.1	5.56	3.24	6.42	36.5	2.25	18.7
JD5-4	ZK83-1,424.00 m	1.79	1.41	344	40.3	142	22.1	3.28	15.4	18.7	83.5	3.42	17.1
JD5-3	ZK75-2,260.90 m	1.68	1.38	438	23.0	35.4	36.1	5.87	5.76	10.2	39.9	2.78	21.4
4样平均值		1.96	1.48	410.50	30.05	90.20	27.08	4.59	8.31	13.06	61.03	3.06	19.15
分析检出限		1.00	0.20	1.00	0.20	0.50	1.00	2.90	0.003	0.80	1.20	0.50	0.20

样号	取样位置	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	Y
LY16-17	ZK91-1,488.30 m	19.6	44.1	5.23	19.1	4.19	0.51	4.76	0.63	2.98	0.6	1.54	0.25	1.41	0.20	15.9
LY16-18	ZK67-1,312.70 m	6.05	13.7	1.60	5.83	1.57	0.12	1.82	0.28	1.32	0.26	0.66	0.12	0.79	0.12	7.57
JD5-4	ZK83-1,424.00 m	19.7	44.3	5.05	18.2	4.15	0.44	4.70	0.62	3.04	0.58	1.52	0.22	1.42	0.18	15.3
JD5-3	ZK75-2,260.90 m	6.72	15.6	1.83	6.74	1.77	0.15	1.96	0.32	1.59	0.31	0.75	0.15	0.89	0.14	8.45
4样平均值		13.02	29.43	3.43	12.47	2.92	0.31	3.31	0.46	2.23	0.44	1.12	0.19	1.13	0.16	11.81
分析检出限		0.05	0.01	0.01	0.05	0.02	0.01	0.05	0.03	0.02	0.03	0.01	0.03	0.01	0.02	0.03