| 西昆仑库地蛇绿岩富Al型豆荚状铬铁矿床成因 |
| |
| 引用本文： | 刘建国,王建.西昆仑库地蛇绿岩富Al型豆荚状铬铁矿床成因[J].地质学报,2016,90(6):1182-1194. |
| |
| 作者姓名： | 刘建国 王建 |
| |
| 作者单位： | 吉林大学,吉林大学 |
| |
| 摘 要： | 西昆仑库地蛇绿岩发育小规模的铬铁矿床,矿体呈豆荚状和层状、似层状,均与纯橄岩紧密伴生。这些纯橄岩主要由橄榄石和副矿物尖晶石组成,与方辉橄榄岩相比,橄榄岩中的橄榄石粒径粗(平均2.5mm),Mg#(88~90)低,这与它们全岩低Mg#(90)值,富Al_2O_3、TiO_2、Cr_2O_3、Fe_2O_3相吻合,与熔融残余成因的纯橄岩明显不同,反映了其很可能是由熔体与方辉橄榄岩反应而成。矿体主要由块状、浸染状及脉状铬铁矿石组成;铬铁矿石中的尖晶石具有低而相对稳定的Cr#(43~56),低于富铬型铬铁矿矿床中的铬铁矿(Cr#60)。块状矿石与纯橄岩呈突变接触,矿石中的尖晶石呈浑圆状,包裹有较多橄榄石、辉石等硅酸盐矿物及角闪石等含水硅酸盐矿物;浸染状铬铁矿石中的尖晶石与橄榄石颗粒构成交织结构,或呈云朵状,沿橄榄石颗粒边界相互连接,矿石的结构构造显示了熔/岩反应成因特征。通过计算分析,我们认为该区富铝型铬铁矿石是由拉斑玄武质熔体与地幔橄榄岩反应而成,由于熔体中含有较高的H_2O,参与反应的熔体可能源于弧后扩张脊环境。
|
| 关 键 词： | 豆荚状铬铁矿 蛇绿岩 熔/岩反应 库地 新疆 西昆仑 |
| 收稿时间： | 2014/11/9 0:00:00 |
| 修稿时间： | 2/1/2015 12:00:00 AM |
Formation of Al Rich Type Podiform Chromitites in the Kudi Ophiolite |
| |
| LIU Jianguo and WANG Jian.Formation of Al Rich Type Podiform Chromitites in the Kudi Ophiolite[J].Acta Geologica Sinica,2016,90(6):1182-1194. |
| |
| Authors: | LIU Jianguo and WANG Jian |
| |
| Institution: | Jilin University,Jilin University |
| |
| Abstract: | Small scale chromite deposit was discovered in Kudi ophiolite, western Kunlun orogenic belt. Orebodies are in podiform and stratiform, which closely associate with dunite. These dunites consist of olivines and spinels. Dunites contain coarser olivines and lower Mg# olivine (88~90) than those in harzburgites, consistent with their low Mg# (less than 90) and relatively high Al2O3, TiO2, Cr2O3 and Fe2O3 in bulk-rock composition when compared with harzburgite, indicating that they are likely the interaction product of melt/harzburgite, rather than residue of mantle peridotite after highly partial melting. Orebody is composed of massive, disseminated and veined chromitites, of which spinels have relatively uniform Cr# ranging from 43 to 56, lower than those of chromites in high-Cr chromitite. In massive ores, they show sharp contact relationships between dunite envelop and chromitite with many silicates (e.g., olivine and pyroxene) as well as hydrous minerals (amphiboles) hosted in rounded spinel grains. In disseminated ores, spinel and olivine grains show interlocking texture, or cloud-shape spinel aggregations directly contact with olivine along grain boundaries. The structures and textures of chromitites in Kudi ophiolite suggest that they were formed through melt/rock interaction. Based on systematic calculation and comprehensive analysis, we consider that the Al-rich type chromitites of Kudi ophiolite are most likely to be interaction products of tholeiitic melt/mantle peridotites with the melt likely derived from back-arc spreading ridge considering its high H2O content. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地质学报》浏览原始摘要信息 |
| 点击此处可从《地质学报》下载免费的PDF全文 |
|
