皖南休宁县石岭头一带花岗质小岩株形成时代重新厘定

刘秀; 余心起; 陈子微; 李鹏举; 周术召; 杨鑫鹏

皖南休宁县石岭头一带花岗质小岩株形成时代重新厘定

1.
中国地质大学(北京)地球科学与资源学院, 北京 100083

2.
四川理工学院经济与管理学院, 四川自贡 643000

基金项目:
国家自然科学基金项目《浙赣皖相邻区中生代推（滑）覆构造特征及其时序分析》（批准号：41872201）

详细信息

作者简介: 刘秀(1990-), 男, 在读博士生, 构造地质学专业。E-mail:didaliuxiu@sina.com

通讯作者: 余心起(1962-), 男, 教授, 博士生导师, 构造地质学专业。E-mail:yuxinqi@cugb.edu.cn

中图分类号: P588.12⁺1

收稿日期: 2018-08-03

修回日期: 2018-10-10

刊出日期: 2019-03-15

Redetermination of the age of granitic stocks in Silingtou area, Xiuning Country, southern Anhui Province

1.
School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China

2.
School of Economics and Management, Sichuan University of Science & Engineering, Zigong 643000, Sichuan, China

More Information

Corresponding author: YU Xinqi, yuxinqi@cugb.edu.cn

Received Date: 03 August 2018

Revised Date: 10 October 2018

Publish Date: 15 March 2019

摘要

摘要:
前人对皖南休宁县石岭头花岗质小岩株进行了K-Ar测年，结果为133.4Ma，属于早白垩世。笔者近期的野外地质调查发现，这些花岗质小岩株含过铝矿物堇青石，岩性特征与休宁花岗闪长岩体非常相近，为中粗粒花岗闪长岩，且见有变形，局部片理化明显。分别在休宁花岗闪长岩体内部和北部外叶村河中采集测年样品进行测定，获得休宁花岗闪长岩体内部835.4±32Ma和外叶小岩株841±29Ma的年龄，二者在误差范围内基本一致，表明它们属于同期岩体。岩石地球化学数据显示，花岗质小岩株具有与休宁花岗闪长岩体类似的地球化学特征，亏损Nb、Ta、Sr等高场强元素，富集K、Ru、Ba、U、Th，且均为强过铝质。结合前人所测休宁岩体数据对比分析，认为这些原先被认为早白垩世的花岗岩是新元古代的产物，为晋宁期休宁岩体的一部分，同时休宁岩体北界应北移约2km。其上覆盖的南华系休宁组砂岩应为超覆沉积形成。
- 新元古代 /
- 花岗质小岩株 /
- 锆石U-Pb测年 /
- 休宁花岗闪长岩 /
- 皖南
Abstract:
The small granitic stocks in Xiuning granodiorite have K-Ar age of 133.4Ma, suggesting that these stocks were formed in Early Cretaceous. During recent field geological survey, the authors found that these small stocks contain aluminum mineral cordierite, and their lithologic characteristics are very similar to those of Xiuning granodiorite. They are all coarse grained granodiorite with local deformation and obvious schistosity. Samples collected from both internal Xiuning granodiorite and Waiye stock yielded LA-ICP-MS zircon U-Pb age of 835.4±32Ma for Xiuning granodiorite and 841±29Ma for Waiye rock, showing that they were formed during the same period. In addition, these small granitic stocks have similar geochemical characteristics to Xiuning granodiorite. Whole-rock geochemical data show that both samples are characteristics by lower HFSE Nb, Ta, Sr and higher K, Ru, Ba, U, Th, and thus belong to the peraluminous S-type granite. By comparative analysis of lithology characteristics, U-Pb age and geochemical data from previous study and this paper, the authors confirm that these stocks should intruded during the Neoproterozoic as a part of the Jinningian Xiuning pluton, not in the Early Cretaceous as previously thought. And the northern boundary of Xiuning pluton must have migrated northward for about 2km. The sandstone (no conglomerate) of Xiuning Formation resulted from the transgressive deposition on these stocks.
- Neoproterozoic /
- granitic stock /
- U-Pb zircon dating /
- Xiuning granodiorite /
- southern Anhui Province

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图 1 皖南休宁岩体地区地质简图(据参考文献①修改)

Figure 1.

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图 2 D252休宁兰渡外叶村花岗闪长岩野外照片

Figure 2.

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图 3 休宁岩体和外叶花岗质小岩株稀土元素球粒陨石标准化配分曲线(a)及微量元素原始地幔标准化蛛网图(b)(标准化数据据参考文献[10])

Figure 3.

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图 4 休宁岩体(D052)和外叶花岗质小岩株(D252)锆石阴极发光(CL)图像及微区U-Pb年龄分析点位

Figure 4.

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图 5 休宁花岗闪长岩锆石U-P谐和图(a、c)及年龄加权平均值示意图(b、d)

Figure 5.

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图 6 休宁组陆源碎屑沉积示意图

Figure 6.

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表 1 外叶和休宁花岗闪长岩主量、微量和稀土元素地球化学数据

Table 1. Petrochemical and geochemical data of Waiye and Xiuning granodiorite

样品	03WN33*	03WN 35*	03HN49*	03HN51*	WN350**	D052	D252-y1	D252-y2	D252-y3
SiO₂	68.95	68.61	70.24	70.96	75.71	69.6	68.91	66.73	68.47
TiO₂	0.42	0.41	0.34	0.29	0.71	0.5	0.46	0.58	0.56
Al₂O₃	15.63	15.77	15.21	14.73	12.61	15	15.37	16.37	15.23
FeO^-	3.28	3.4	2.79	2.63	2.68	3.74	3.33	3.81	3.89
MnO	0.06	0.05	0.05	0.05	0.02	0.06	0.066	0.065	0.068
MgO	1	1.24	0.97	1.05	0.5	1.17	1.09	1.34	1.30
CaO	1.36	0.8	0.8	0.97	0.15	0.68	0.72	0.89	1.03
Na₂O	2.47	2.73	2.63	2.88	0.14	2.94	3.20	3.24	3.03
K₂O	4.18	3.93	4.12	3.68	4.21	3.96	4.63	4.45	3.49
P₂O₅	0.21	0.24	0.16	0.19	0.06	0.2	0.18	0.19	0.19
烧失量	1.88	2.31	2.2	2.11	2.6	1.73	1.86	2.16	2.62
总计	99.44	99.49	99.51	99.54	99.39	99.73	99.83	99.81	99.88
A/CNK	1.41	1.55	1.49	1.4	2.56	1.45	1.40	1.49	1.57
Mn	413.8	383.7	397.2	419.2	154.93	464.79	514.74	503.79	525.15
Ni	13.07	16.49	10.4	11.82	9.56	-	13.4	16.2	16.9
Ga	17.62	19.58	17.46	17.59	17.4	18.8	16.6	18.1	17.7
Rb	133.8	151	130	132.1	142	139	138	111	127
Ba	808.3	620.3	894.8	670.9	466	724	879	910	380
Th	9.31	9.11	8.84	7.07	-	11.2	9.09	8.75	10.7
Nb	8.67	9.87	7.17	7.23	12	9	9.34	10.7	8.92
Ta	0.67	0.72	0.58	0.49	0.96	0.7	0.61	0.70	0.60
Hf	4.58	4.96	4.54	3.72	3.8	5	6.94	6.50	7.83
U	2.52	2.52	1.53	1.04	2.54	1.78	2.06	1.28	1.96
Sr	161	189.4	196.3	179	29.2	184.5	180	175	135
Zr	164.7	186.1	144.9	142.4	128	171	169	186	203
Y	24.26	33.68	25.64	25.07	26.2	22.9	21.8	20.8	29.6
La	24.49	27.39	24.32	22.45	33.3	28.2	21.2	29.3	41.1
Ce	51.8	56.85	50.91	47.97	70.2	64	51.0	63.5	82.8
Pr	6.73	7.42	6.67	6.01	8.17	7.15	6.08	8.46	10.3
Nd	26.05	28.5	25.51	22.39	32.2	27.1	25.0	34.6	41.3
Sm	5.83	6.27	5.53	4.97	6.31	6.03	5.35	7.20	8.68
Eu	1	1.07	1.07	0.89	1.11	1.16	1.12	1.43	1.20
Gd	5.48	5.62	4.97	4.21	4.94	5.91	4.58	5.82	7.34
Tb	0.88	0.92	0.8	0.71	0.88	0.93	0.84	0.95	1.21
Dy	4.53	5.14	4.46	3.69	5.44	4.42	4.52	4.48	6.02
Ho	0.9	0.95	0.89	0.68	1.02	0.89	0.80	0.76	1.07
Er	2.4	2.43	2.38	1.72	2.83	2.26	2.03	1.80	2.73
Tm	0.36	0.39	0.39	0.26	0.42	0.33	0.35	0.27	0.45
Yb	2.44	2.56	2.41	1.65	2.72	0.93	2.05	1.54	2.68
Lu	0.4	0.35	0.39	0.23	0.37	0.31	0.30	0.24	0.41
注:03WN33、03WN35、03WN49、03WN51四组数据来自于吴荣新等^[7]; WN350**数据来自于薛怀民等^[1]; 主量元素含量单位为%, 微量和稀土元素含量单位为10^-6

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表 2 休宁和外叶花岗闪长岩 LA-ICP-MS锆石 U-Th-Pb分析结果

Table 2. LA-ICP-MS zircon U-Th-Pb analytical results of Xiuning and Waiye granodiorite



注：带删除线数据不参与计算

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