北秦岭灰池子花岗质复式岩体的源岩讨论——元素-同位素地球化学制约

李伍平; 王涛; 王晓霞

北秦岭灰池子花岗质复式岩体的源岩讨论——元素-同位素地球化学制约

李伍平^{1, 2},
王涛³,
王晓霞²

1.
中国科学院广州地球化学研究所, 广东广州 510640
2.
长安大学地球科学系, 陕西西安 710054
3.
北京大学地质学系, 北京 100871

基金项目:

国家自然科学基金项目 40072064

详细信息

作者简介:
李伍平(1963), 男, 1999年毕业于中国地质大学地球科学学院, 获博士学位, 主要从事区域地质和岩石学研究

中图分类号: P591.1
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出版历程
- 收稿日期: 2000-03-20
- 刊出日期: 2001-05-25

SOURCE OF HUICHIZI GRANITOID COMPLEX PLUTON IN NORTHERN QINLING, CENTRAL CHINA: CONSTRAINED IN ELEMENT AND ISOTOPIC GEOCHEMISTRY

1.
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
2.
Department of Earth Science, Chang'an University, Xi'an 710054
3.
Department of Geology, Peiking University, Beijing 100871, China

摘要

摘要: 灰池子复式岩体是北秦岭造山带核部规模最大的花岗岩体, 它由3个深成岩体组成.花岗岩具有高SiO₂ (6 6.86 %~ 73.48%), Al₂O₃ (14.44 %~ 16.32 %) 和Na₂O (4.17%~4.78%), 低TiO₂ (< 0.74%), MgO (< 1.18%) 和K₂O (< 3.33 %) 的特征.花岗岩轻稀土元素富集(27.45 < w (La)_N/w (Yb)_N < 72.99), Eu为负—弱正异常, 微量元素Y的质量分数为(3.70~9.77)×10^-6, Yb为(0.30~ 1.14)×10^-6, Sr为(310~ 775)×10^-6, w (Sr) /w (Y) 为47.87~ 114.36, 大离子亲石元素(Rb, Ba, Th, Sr等) 相对富集, 高场强元素(Nb, Ta, Ti, Zr) 相对亏损.同位素组成比较均匀, 0.5 12 31 < w (¹⁴³Nd) /w (¹⁴⁴Nd) < 0.5 12 38, 0.70 783 < w (⁸⁷Sr) /w (⁸⁶Sr) < 0.70 880, 0.95Ga < t_DM < 1.0 9Ga, - 0.81 < ε (Nd, 437Ma) < 0.93, 且18 < ε (Sr, 437Ma) < 32, 这些特征与Adakitic质岩相似.笔者认为灰池子花岗岩是由深部下地壳新元古代玄武质岩石部分熔融形成的Adakitic质岩, 其形成与晚加里东—早海西期北秦岭杂岩地体南北裂陷海盆发生陆内双向俯冲有关.
- 灰池子复式岩体 /
- Adakitic质岩 /
- 下地壳 /
- 部分熔融 /
- 晚加里东—早海西期 /
- 北秦岭
Abstract: Huichizi complex pluton, the largest granitoid pluton in the core of northern Qinling orogenic belt, is composed of three sequences. These granitoid rocks have higher SiO₂ (66.86%-73.48%), Al₂O₃ (14.44%-16.32%), abundant Na₂O (4.17%-4.78%), and lower TiO₂ (< 0.74%), MgO (< 1.18%) and K₂O (< 3.33%) mass fraction, and more enriched in LREE (27.45 < w (La)_N/ w (Yb)_N < 72.99), and distinct negative and weak positive Eu anomaly. In these granitoid rocks, Y, Yb, Sr mass fractions and w (Sr) / w (Y) ratio of trace elements vary respectively from 3.70×10^-6 to 9.77×10^-6 (< 18×10^-6), 0.30×10^-6 to 1.14×10^-6 (< 1.90×10^-6), 310×10^-6 to 775×10^-6 and 47.87 to 114.36. While those of Huichizi complex display multi element patterns with large positive ion lithophile elements (Rb, Ba, Th and Sr) anomalies and high negative field strong elements (Nb, Ta, Ti and Zr) anomalies and indicate the geochemical characteristics of calc alkalic granites and volcanic arc granites. All the granitoid rocks exhibit a similar range of Nd and Sr isotopic ratios: 0.512 31 < w (¹⁴³Nd) / w (¹⁴⁴Nd) < 0.512 38), 0.707 83 < w (⁸⁷Sr) / w (⁸⁶Sr) < 0.708 80, 0.95 Ga < t_DM (depleted mantle model age) < 1.09 Ga, -0.81 < ε (Nd, 437 Ma) < 0.93 and 18 < ε (Sr, 437 Ma) < 32, and show the source of Huichizi complex from basic rocks. These characteristics are similar to those of the Adakitic rocks. The authors think that the granitoid rocks of Huichizi complex may have been the result of the subduction of the southern intracontinent rift along the Danfeng Shangnan fault by a north dipping of the northern intracontinent rift (Erlangping rift) and that along the Zhuyangguan Xiaguanying fault by a south dipping under the Northern Qinling block during late Caledonian-early Hercynian period. This subduction of the intracontinent rifts leads to the partial melting of Late Proterozoic underplating basic rocks of lower crust and the formation of the granitoid rocks of Huichizi complex.
- Huichizi complex pluton /
- Adakitic rocks /
- lower crust /
- partial melting /
- late Caledonian-early Hercynian /
- northern Qinling

HTML全文

图 1 灰池子花岗质复式岩体区域地质简图

1.峡河岩群; 2.秦岭岩群; 3.明朗河岩体草沟单元; 4.明朗河岩体下庄单元; 5.明朗河岩体东沟单元; 6.淇河岩体颜坪单元; 7.淇河岩体黄泥盖单元; 8.淇河岩体南坪单元; 9.蔡家沟岩体姚家岔单元; 10.蔡家沟岩体后拐岔单元; 11.蔡家沟岩体谷谷庵单元; 12.采样位置及编号; 13.平移断层; 14.片麻理产状; 15.叶理产状; 16.韧性剪切带; 17.涌动型侵入接触界线; 18.脉动型侵入接触界线; 19.高压、超高压变质带

Fig. 1. Regional geological map of Huichizi granitoid complex pluton in northern Qinling, Central China

下载: 全尺寸图片幻灯片

图 2 灰池子复式岩体花岗岩稀土元素配分曲线(球粒陨石标准值见文献[34])

Fig. 2. Chondrite-normalized REE patterns for granites of Huichizi complex pluton

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图 3 灰池子复式岩体花岗岩微量元素蛛网图(原始地幔标准值见文献[34])

Fig. 3. Primitive mantle-normalized spider diagram for granites of Huichizi complex pluton

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图 4 w (Y+Nb) /w (Rb) 关系图解(据Pearce等^[42])

Fig. 4. w (Y+Nb) vs w (Rb) diagramVAG.火山弧花岗岩; S-COLG.同碰撞花岗岩; ORG.洋中脊花岗岩; WPG.板内花岗岩

下载: 全尺寸图片幻灯片

表 1 灰池子复式岩体花岗岩和秦岭岩群变质岩主量元素分析结果

Table 1. Analysis data of major elements for granites of Huichizi complex pluton and for metamorphic rocks of Qinling Group

表 2 灰池子复式岩体花岗岩CIPW标准矿物计算

Table 2. CIPW standard minerals calculated data for granites of Huichizi complex pluton

表 3 灰池子复式岩体花岗岩和秦岭岩群变质岩微量元素分析结果

Table 3. Analysis data of trace elements for granites of Huichizi complex pluton and for metamorphic rocks of Qinling Group

表 4 灰池子复式岩体花岗岩同位素分析结果

Table 4. Nd and Sr isotopic analysis data for granites of Huichizi complex pluton

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