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| 青藏高原西部甜水海地区白垩纪花岗岩类的岩石学地球化学特征及其地质意义 | |
| 引用本文： | 王春英,蔺新望,张俊良,王世炎.青藏高原西部甜水海地区白垩纪花岗岩类的岩石学地球化学特征及其地质意义[J].地质通报,2009,28(5):585-593. |
| 作者姓名： | 王春英 蔺新望 张俊良 王世炎 |
| 作者单位： | 1. 中国地质大学地球科学与资源学院,北京,100083;山西省第三地质工程勘察院,山西,榆次,030600 2. 陕西省地质调查院,陕西,西安,710016 3. 河南省地质调查院,河南,郑州,450001 |
| 基金项目： | 中国地质调查局国土资源大调查综合研究项目 |
| 摘 要： | 甜水海地区广泛分布白垩纪的中酸性侵入岩，可分为早白垩世（123Ma）、晚白垩世早期（100~93Ma）和晚白垩世晚期（79~74Ma）3期。早期侵入体零星，为正长花岗岩、二云母花岗岩及含石榴子石花岗岩，属高钾钙碱性系列，A/CNK大于1.1，K2O含量大于Na2O，负Eu异常明显，刚玉分子数大于1.1，属于典型的强过铝质S型花岗岩。晚白垩世早期花岗岩分布广泛，以英云闪长岩和花岗闪长岩为主，主要属中—高钾钙碱性系列，个别属于钾玄岩系列，A/CNK主体小于1.15，负Eu异常中等，刚玉分子数多小于1.1，主体属I型花岗岩。晚白垩世晚期花岗岩同样分布广泛，为花岗闪长岩、二长花岗岩组合，主要属于高钾钙碱性系列，个别为中钾钙碱性系列，A/CNK主体大于1.05，负Eu异常较明显，刚玉分子数多大于1.1，主体属于典型的S型花岗岩。综合分析认为，甜水海地区白垩纪中酸性侵入岩与班公湖-怒江残余洋盆消减、闭合有关，可能记录了羌塘-冈底斯带之间的同碰撞（早期）、碰撞后（晚白垩世）等构造岩浆演化过程。 |
| 关 键 词： | 花岗岩类 岩石学 地球化学 白垩纪 甜水海地区 西藏西部 |
Petrographical and geochemical characteristics of the Cretaceous granitoids in the Tianshuihai area, western Qinghai-Tibet Plateau, China and its geological significance. Geological Bulletin of China |
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| Wang C Y,Lin X W,Zhang J L,Wang S Y.Petrographical and geochemical characteristics of the Cretaceous granitoids in the Tianshuihai area, western Qinghai-Tibet Plateau, China and its geological significance. Geological Bulletin of China[J].Geologcal Bulletin OF China,2009,28(5):585-593. | |
| Authors: | Wang C Y Lin X W Zhang J L Wang S Y |
| Institution: | School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China |
| Abstract: | The Cretaceous intermediate-acid intrusive rocks are widely distributed in Tianshuihai, those rocks can be divided into three categories as per different age: early Cretaceous (123Ma), the early stage of Late Cretaceous (100-93Ma) and the late stage of Late Cretaceous. The early Cretaceous intrusive bodies are sporadic and dominated by orthoclase granite, two-mica granite and granite containing garnet, which belong to high-K calc-alkaline type. The A/CNK ratios are more than 1.1, the contents of K2O are more than those of Na2O, negative Eu anomalies are obvious, the molecular numbers of corundum are more than 1.1, all these facts indicate that they belong to the typical peraluminum S type granitoids. Granitoids from the early stage of late Cretaceous are also widely distributed dominated by tonalite and granodiorite, which mainly belong to medium-high potassium and calcium alkaline types, some of them belong to potassium basalt. Generally A/CNK ratios are less than 1.15, negative Eu anomalies are medium, molecular numbers ofcorundum are less than 1.1 and they mainly belong to I type granitoids. Granitoids from the Late stage of Late Cretaceous are widely distributed which dominated by granite diorite and ultimate-granite, mainly belong to high-potassium calcium alkaline type, some of them belong to medium-potassium calcium type. A/CNK ratios are over 1.05 with noticeable Eu negative anomalies, the molecular numbers of corundum are more than 1.1 and generally belong to S type. It is concluded after comprehensive analysis that the Cretaceous intrusive rocks in the Tianshuihai area are closely linked to the reduction and closure of Bangonghu-Nujiang residual ocean basin, and their formation may keep record of those syn-collision or post-collison structural magmatic evolution between Qiangtang-Gangdisi belt. |
| Keywords: | granitoid rocks petrography geochemistry Cretaceous Tianshuihai area western Tibet |
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