华北克拉通南缘太古—元古宙界线安沟群火山岩的年龄及地球化学

高山; 周炼; 凌文黎; 刘勇胜; 周鼎武

华北克拉通南缘太古—元古宙界线安沟群火山岩的年龄及地球化学

高山^{1, 2,},
周炼²,
凌文黎²,
刘勇胜¹,
周鼎武¹

1.
中国地质大学地质过程与矿产资源国家重点实验室, 湖北武汉 430074
2.
西北大学地质学系教育部大陆动力学重点实验室, 陕西西安 710069

基金项目:

国家自然科学基金自由申请项目 40373013

详细信息

作者简介:
高山(1962-), 男, 教授, 博士生导师, 主要从事岩石圈地球化学研究.E-mail: gaoshan@cug.edu.cn

中图分类号: P59
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出版历程
- 收稿日期: 2005-01-16
- 刊出日期: 2005-05-25

Age and Geochemistry of Volcanic Rocks of Angou Group at the Archean-Proterozoic Boundary

1.
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
2.
Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China

摘要

摘要: 河南登封地区登封群和安沟群记录了华北克拉通南缘太古宙—元古宙界线两侧地层较完整的演化历史.Kröner et al.(1988)曾获得登封群顶部老羊沟组变英安岩中锆石的SHRIMP年龄为(2 512±12)Ma.本研究获得不整合覆盖在登封群之上的安沟群同源双峰式拉斑玄武岩和英安岩7个样品全岩Sm-Nd同位素等时线年龄为(2 507± 96)Ma, MSWD=6.3, 初始¹⁴³Nd/¹⁴⁴Nd=0.509 560±0.000 093, ε_Nd(2.5 Ga)=3.27±1.82.上述年龄制约了登封群顶部长英质火山岩与安沟群底部的双峰火山岩之间的年龄相差最多应不超过113 Ma.安沟群演化程度较低的拉斑玄武岩La/Nb比值为0.66~ 1.14, 与软流圈地幔的比值接近, 而明显不同于岛弧玄武岩(La/Nb < 2.0).结合安沟群火山岩的双峰特征, 这些说明太古宙末或元古宙初期至少华北克拉通南缘已进入陆内裂谷伸展环境.
- 华北克拉通 /
- 太古宙 /
- 双峰火山岩 /
- SmNd同位素
Abstract: The Dengfeng Group and Angou Group from the Dengfeng area, Henan Province preserve rocks at the Archean- Proterozoic boundary. Kröner et al.(1988) yielded an SHRIMP U-Pb zircon age of (2 512± 12) Ma for a date from the up- per Dengfeng Group. Here we report an Sm-Nd whole rock isochron age of (2 507± 96) Ma (MSWD= 6.3) for 7 volcanic rocks from the Angou Group with initial ¹⁴³Nd/¹⁴⁴Nd= 0.509 560± 0.000 093, which corresponds to ε_Nd(2.5 Ga)= 3.27± 1.82. This constrains an age difference of less than 113 Ma between the top of Dengfeng and the bottom of Angou volcanic rocks. The less evolved Angou metatholeiites are characterized by asthenospheric La/Nb ratios (< 2.0). Together with the bimodal character, it is inferred that the Angou Group formed in a continental rift setting.
- North China craton /
- Archean /
- bimodal volcanic rocks /
- Sm-Nd isotope

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图 1 河南临汝县寨沟地区地质简图(据孙枢等(1985)简化)

1.晚太古代太华群; 2.早元古代安沟群寨沟组; 3.早元古代安沟群石梯沟组; 4.中上元古界—寒武系; 5.中上元古界; 6.第四系; 7.闪长岩; 8.花岗岩; 9.断层

Fig. 1. Geological sketch map of Zhaigou area in Lingru county, Henan Province

下载: 全尺寸图片幻灯片

图 2 登封群和安沟群地层柱状图(不同岩性地层厚度资料参考孙枢等(1985))

GJY.郭家窑组; JGM.金家门组; LYG.老羊沟组; STG.石梯沟组; ZG.寨沟组

Fig. 2. Stratigraphic column of the Dengfeng Group and Angou Group

下载: 全尺寸图片幻灯片

图 3 安沟群双峰火山岩的稀土元素分配模式

Fig. 3. Chondrite-normalized REE patterns of volcanic rocks from the Angou Group

下载: 全尺寸图片幻灯片

图 4 安沟群双峰火山岩Sm-Nd等时线图

Fig. 4. Sm-Nd isochron age for volcanic rocks from the Angou Group

下载: 全尺寸图片幻灯片

表 1 安沟群火山岩的主量元素成分

Table 1. Major element compositions of volcanic rocks from the Angou Group

表 2 安沟群火山岩的微量和稀土元素成分

Table 2. Trace and rare earth element compositions of volcanic rocks from the Angou Group

表 3 安沟群火山岩的Sm-Nd同位素组成

Table 3. Sm-Nd isotope compositions of volcanic rocks from the Angou Group

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