昆秦接合部志留-泥盆纪侵入岩及其构造环境

张智勇; 张克信; 朱云海; 王瑾

昆秦接合部志留-泥盆纪侵入岩及其构造环境

张智勇^{1, 2},
张克信¹,
朱云海¹,
王瑾²

1.
中国地质大学(武汉)地球科学学院, 湖北武汉 430074
2.
青海省地质调查院, 青海西宁 810012

基金项目:

中国地质调查局“1∶25万兴海幅区域地质调查”项目 19961300010122

高等学校全国优秀博士学位论文作者专项资金项目 200228

详细信息

中图分类号: P588
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出版历程
- 收稿日期: 2004-10-15
- 刊出日期: 2005-03-25

Silurian-Devonian Intrusive Rocks and Tectonic Environment in Copulae of Kunlun-Qinling Mountains

1.
Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China
2.
Geological Survey Institute of Qinghai, Xining 810012, China

摘要

摘要: 通过详细的地质填图和年代学研究,确定昆秦接合部存在志留-泥盆纪岩浆活动,采用单颗粒锆石U-Pb定年方法测定侵入岩的形成时代为382~423Ma,即志留-泥盆纪.岩体以小岩株、岩脉及构造岩片产出,普遍受后期构造作用,多数以构造片岩卷入海西期苦海-赛什塘构造混杂岩带内.岩性有石英闪长岩、英云闪长岩、花岗闪长岩及二长花岗岩4种,属于典型的钙碱性系列.常量和微量元素特征及构造环境判别显示,其形成于岛弧或陆缘弧及同碰撞构造环境,反映了原特提斯洋壳俯冲消减及随后的陆壳碰撞过程.该阶段侵入岩在侵入时代和形成的构造环境上,与东昆仑早古生代岩浆活动一致,因此,昆秦接合部发育的志留-泥盆纪岩浆弧向西可与东昆仑早古生代岩浆岩带相接.志留-泥盆纪侵入岩产出的地质特征及其形成的构造环境进一步说明,昆秦接合部地区古特提斯多岛小洋盒形成于弧后扩张作用,与原特提斯洋的关闭紧密相关.
- 侵入岩 /
- 志留-泥盆纪 /
- 昆秦接合部 /
- 构造环境
Abstract: Silurian-Devonian magmatic activity was discovered in the copulae of the Kunlun-Qinling mountains by detailed mapping and chronology analysis. Single grain zircon U-Pb dating yielded formation dates of 382-423 Ma in the intrusive rocks, which is Silurian-Devonian. The intrusive bodies are output in stocks, dikes and tectonic slices, which were suffered from later tectonism and evolved in the Kuhai-Saishitang Hercynian mélange belt as tectonic slices. The rock types are quartz-diorite, tonalite, granodiorite and monzonite granite, belonging to typical calc-alkali rocks. The characteristics of trace elements, main elements and tectonic environment discrimination reveal that the rocks were formed in an island arc tectonic environment or a continental margin arc tectonic environment. Some were also formed in a syncollisional tectonic environment, which reflects the stages of the prototethys ocean subduction and later continental crust collision. In that period intrusive rocks are in accordance with the East Kunlun Early Paleozoic magmatic activity zone, so it is suggested that a Silurian-Devonian magmatic arc developed in the copulae between the Kunlun-Qinling mountains, which joins the East Kunlun Early Paleozoic magmatic rock zone to the west. The geological characteristics and tectonic environment of the Silurian-Devonian intrusive rock in the copulae between Kunlun-Qinling Mountains indicated that the Paleotethys archipelagic ocean was formed in back-arc expandation, which was closely related to the close of the prototethys ocean.
- intrusive rock /
- Silurian-Devonian /
- copulae of Kunlun-Qinling mountains /
- tectonic environment

HTML全文

图 1 昆秦接合部构造单元及志留-泥盆纪侵入岩分布

1.裂解基底岩片; 2.蛇绿岩; 3.第四系; 4.滑脱带构造单元边界; 5.走滑断层; 6.逆冲带构造单元边界; 7.逆冲断层; 8.采样位置及同位素年龄; 9.岩体位置; Pt₁b.白沙河岩组; TL.隆务河群; TH.洪水川群; γδ^T3.晚三叠世花岗闪长岩; 构造岩片: Sch.龙通片岩(Pt₁b); lgn.沙乃亥片麻岩(Pt₁); Yβ.雅日玄武岩(P); Psmo.塞日科龙洼蛇绿混杂岩(P); Pms.雪穷糜棱片岩(P); Pmav.曲龙中酸性火山岩(P); Ptu.双龙浊积岩(P); 志留-泥盆纪花岗岩: δo^S3.喔尔日石英闪长岩; oγ^S3.曲龙英云闪长岩; δo^D1.乎若合石英闪长岩; γδ^D1.唉呀日山花岗闪长岩; ηγ^D1.扎那合惹二长花岗岩

Fig. 1. Tectonic unit and S-D intrusive rock distribution in copulae of Kunlun-Qinling mountain

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图 2 w (SiO₂)-AR图

Fig. 2. w (SiO₂)-AR diagram

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图 3 稀土配分曲线和微量元素蛛网图(球粒陨石标准化值据Taylor and Mclennan, 1985;洋脊花岗岩值据Pearce et al., 1984)

Fig. 3. REE distribution patterns and spider diagram of trace elements

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图 4 U-Pb年龄曲线谐和图

Fig. 4. U-Pb age concordant curve

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图 5 花岗岩R₁-R₂图解(Batchelor and Bowden, 1985)

1.地幔分异花岗岩; 2.碰撞前花岗岩; 3.碰撞后隆起花岗岩; 4.造山晚期—晚造山期花岗岩; 5.非造山区花岗岩; 6.同碰撞花岗岩; 7.造山后花岗岩

Fig. 5. R₁-R₂ diagram for granites

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图 6 花岗岩w (Nb)-w (Y)、w (Rb)-w (Y+Nb) 判别图(Pearce et al., 1984)

Fig. 6. w (Nb)-w (Y) and w (Rb)-w (Y+Nb) discrimination diagram for granites

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表 1 志留-泥盆纪侵入岩常量元素(10^-2)、稀土元素及微量元素分析(10^-6) 结果

Table 1. Analyses results of major, trace and rare earth elements from S-D intrusive rocks

表 2 侵入岩单颗粒锆石铀-铅年龄测定结果

Table 2. Single grain Zircon U-Pb dating results of intrusive rocks

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