| 新疆阿尔泰可可托海3号伟晶岩脉岩浆—热液演化和成因 |
| |
| 引用本文： | 朱金初,吴长年,刘昌实,李福春,黄小龙,周东山.新疆阿尔泰可可托海3号伟晶岩脉岩浆—热液演化和成因[J].高校地质学报,2000,6(1):40-52. |
| |
| 作者姓名： | 朱金初 吴长年 刘昌实 李福春 黄小龙 周东山 |
| |
| 作者单位： | 南京大学 地球科学系；南京大学 内生金属矿床成矿机制研究国家重点实验室 江苏 南京 210093 |
| |
| 基金项目： | 中国科学院资助项目，中国有色金属工业总公司资助项目，49573185;49873017，，， |
| |
| 摘 要： | 新疆阿尔泰可可托海3号伟晶岩脉，由一陡倾斜的巨大岩钟和缓倾斜的板状体联合组成，总 体形态似一实心草帽。其空间分带十分明显，自外向内可依次划分出如下九个共生－结 构带 ：Ⅰ 文象、变文象伟晶岩带；Ⅱ 糖粒状钠长石带；Ⅲ 块状微斜长石带；Ⅳ 白云母-石英 带；Ⅴ 叶钠长石-锂辉石带；Ⅵ 石英-锂辉石（-叶钠长石）带；Ⅶ 白云母-薄片状钠长石 带；Ⅷ 锂云母-薄片状钠长石带；Ⅸ 石英和微斜长石核。根据伟晶岩各共生－结构带的时 空关系、矿物的多世代性和矿物中的包裹体等特征，从岩浆－热液演化的角度，探讨了伟 晶岩的成因问题，认为：Ⅰ、Ⅲ带和部分Ⅱ、Ⅳ带主要是富水但水不饱和的伟晶岩浆 直接结晶的产物；Ⅴ、Ⅵ、Ⅶ带是在晶体相、熔体相和流体相三相并存的条件下，即岩浆— 热液过渡阶段结晶形成的；Ⅸ带是在热液早阶段从高温富硅酸盐溶质的超临界流体中结晶出 来 的；Ⅷ带和部分Ⅱ、Ⅳ带则是热液交代的产物。但交代流体不是从深部外来，而是从伟 晶岩浆体系本身在分异演化过程中发生液相分离的结果。
|
| 关 键 词： | 伟晶岩 空间分带 岩浆－热液演化 岩石成因 |
| 收稿时间： | 2000-03-20 |
| 修稿时间： | 1999-12-15 |
Magmatic-Hydrothermal Evolution and Genesis of Koktokay No.3 Rare Metal Pegmatite Dyke, Altai, China |
| |
| ZHU Jin-chu,WU Chang-nian,LIU Chang-shi,LI Fu-chun,HUANG Xiao-long,ZHOU Dong-shang.Magmatic-Hydrothermal Evolution and Genesis of Koktokay No.3 Rare Metal Pegmatite Dyke, Altai, China[J].Geological Journal of China Universities,2000,6(1):40-52. |
| |
| Authors: | ZHU Jin-chu WU Chang-nian LIU Chang-shi LI Fu-chun HUANG Xiao-long ZHOU Dong-shang |
| |
| Institution: | Department of Earth Sciences and State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China |
| |
| Abstract: | The Koktokay No.3 Li-Be-Ta-Nb-Cs bearing pegmatite dyke of the Upper Paleozoic age is located in the Altai Caledonian-Hercynian fold be lt, Xinjiang Autonomous Region, China. It consists of two major parts: a gent ly dipping “plate”, and a steeply dipping cupola protruding from the plate upw ards. The overall shape of the dyke looks like a solid hat.
The Koktokay pegmatite cupola is emplaced in the amphibolitized gabbro and chara cterized by a well developed internal zonal structure. From the border wall inw ards the following 9 mineralogical-textural zones can be subdivided: Ⅰ. Graphi c and pseudo-graphic pegmatite zone; Ⅱ. Saccharoidal albite zone; Ⅲ. Block y alkali feldspar zone; Ⅳ. Muscovite-quartz zone; Ⅴ. Cleavelandite-spodumene zone; Ⅵ. Quartz-spodumene (-cleavelandite) zone; Ⅶ. Thin sliced albite-mus covite zone; Ⅷ. Lepidolite-thin sliced albite (-pollucite) zone; Ⅸ. Blocky quartz and microcline core.
Studies on the melt inclusions, fluid-melt inclusions and fluid inclusions in t he minerals of pegmatite provide important clues in judging the magmatic-hydr ot hermal evolution history for the pegmatite formation. The quartz, microcline, g arnet and beryl from zones Ⅰ and Ⅲ contain melt inclusions which are homogeni zed at the temperature range of 610℃～900℃. The spodumene, beryl and quartz f rom zones Ⅳ-Ⅶ contain fluid-melt inclusions and fluid inclusions. The cryst al phases in the fluid-melt inclusions comprise albite, quartz, spodumene, bery l and pollucite etc. The coexisting fluid inclusions in these minerals are of H 2O-CO2-NaCl character, with Th of 310℃～420℃. The salinities are high (wi th NaCl and/or KCl crystal) or moderate (10%～18%). The quartz from core zone contains only fluid inclusions, with Th of 300℃～320℃ and salinities of 5%～12 %. All above-mentioned temperature measurements are not pressure corrected. T he formation pressures are estimated as 3.2～1.5kb.
Based on the zonal distribution and textural relationship of mineral assemblages , multiple generations of rock-forming and rare-metal minerals, as well as the features of inclusions and their thermometric data etc， it is interpreted that the zones Ⅰ, Ⅲ and partly Ⅱ、Ⅳ were crystallized from the volatile-undersa turated silicate melt; zones Ⅴ, Ⅵ and Ⅶ were crystallized from the volati le-oversaturated rare metal-rich residual silicate melt at the magmatic-hydro thermal transition stage where the residual melt phase, silicate crystal ph ase and exsolved fluid phase coexist. The blocky quartz and microcline of zone Ⅸ might be directly crystallized from the high temperature supercritical hydrot hermal solution enriched in silicate solute. The zone Ⅷ and partly zones Ⅱ an d Ⅳ might be considered as metasomatic units. However, the metasomatizing hydrothermal solutions were derived from the pegmatitic residual magma system i tself during its crystallization and evolution, but not from the outside environ ment. |
| |
| Keywords: | Altai pegmatite internal zonal structure multiple generations of minerals fluid inclusions magmatic-hydrothermal evolution |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《高校地质学报》浏览原始摘要信息 |
| 点击此处可从《高校地质学报》下载免费的PDF全文 |
|
