...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The American mineralogist >The occurrence of tetrahedrally coordinated Al and B in tourmaline: An 11B and ~(27)Al MAS NMR study
【24h】

The occurrence of tetrahedrally coordinated Al and B in tourmaline: An 11B and ~(27)Al MAS NMR study

机译：电气石中四面体配位的Al和B的存在：一项11B和〜（27）Al MAS NMR研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Considerable uncertainty has surrounded the occurrence of tetrahedrally coordinated Al and B at the T site in tourmaline. Although previously detected in several tourmaline specimens, the frequency of these substitutions in nature, as well as the extent to which they occur in the tourmaline structure, is not known. Using 11B and 27Al MAS NMR spectroscopy, we have investigated the presence of B and Al at the T site in 50 inclusion-free tourmaline specimens of low transition-metal content and different species (elbaite, “fluor-elbaite,” liddicoatite, dravite, uvite, olenite, and magnesiofoitite) from different localities worldwide. Chemical shifts of [4]B and [3]B in 11B spectra, and [4]Al and [6]Al in 27Al spectra, are well resolved, allowing detection of even small amounts of T-site constituents. In the observed spectra, [4]B and [3]B peaks are located at 0 and 18–20 ppm, respectively, with the greatest intensity corresponding to [3]B (=3 apfu). In 27Al spectra, [4]Al and [6]Al bands are located at 68–72 and 0 ppm, respectively, with the greater intensity corresponding to [6]Al. However, inadequate separation of YAl and ZAl precludes resolution of these two bands. Simulation of 11B MAS NMR spectra shows that tetrahedrally and trigonally coordinated B can be readily distinguished at 14.1 T and that a [4]B content of 0.0–0.5 apfu is common in tourmaline containing low amounts of paramagnetic species. 27Al MAS NMR spectra show that Al is also a common constituent of the T site in tourmaline. Determination of [4]Al content by peak-area integration commonly shows values of 0.0–0.5 apfu. Furthermore, the chemical shift of the 27Al tetrahedral peak is sensitive to local order at the adjacent Y and Z octahedra, where [4]Al-YMg3 and [4]Al-Y(Al,Li)3 arrangements result in peaks located at ~65 and ~75 ppm, respectively. Both 11B MAS NMR and 27Al MAS NMR spectra show peak broadening as a function of transition-metal content (i.e., Mn2+ + Fe2+ = 0.01–0.30 apfu) in the host tourmaline. In 11B spectra, broadening and loss of intensity of the [3]B signal ultimately obscures the signal corresponding to [4]B, increasing the limit of detection of [4]B in tourmaline. Our results clearly show that all combinations of Si, Al, and B: T = (Al, Si)6, T = (B, Si)6, T = (Al, B, Si)6, and T = Si6 apfu, are common in natural tourmalines
机译：电气石中T部位四面配位的Al和B的存在存在很大的不确定性。尽管先前已在几个电气石样本中检测到这些，但自然界中这些取代的频率以及它们在电气石结构中出现的程度尚不清楚。使用11B和27Al MAS NMR光谱，我们研究了T部位中B和Al在50个过渡金属含量低且物种不同的无杂质电气石样品中的存在（elbaite，“ fluor-elbaite”，liddicoatite，dravate，全世界的不同地方的辉石，橄榄石和菱镁矿）。 11B光谱中[4] B和[3] B以及27Al光谱中的[4] Al和[6] Al的化学位移得到了很好的解决，甚至可以检测到少量的T位置成分。在观察到的光谱中，[4] B和[3] B峰分别位于0和18-20 ppm，最大强度对应于[3] B（= 3 apfu）。在27Al光谱中，[4] Al和[6] Al谱带分别位于68-72和0 ppm处，强度更大，对应于[6] Al。但是，YAl和ZAl的分离不足会阻止这两个波段的分离。对11B MAS NMR谱的模拟表明，在14.1 T处可以容易地区分四面体和三角配位的B，在电气石中含有少量顺磁性物质，[4] B含量为0.0–0.5 apfu。 27 Al MAS NMR光谱表明，Al也是电气石T部位的常见成分。通过峰面积积分确定[4] Al含量通常显示为0.0–0.5 apfu的值。此外，27Al四面体峰的化学位移对相邻八面体的Y和Z八面体敏感，其中[4] Al-YMg3和[4] Al-Y（Al，Li）3排列导致峰位于〜 65和〜75 ppm。 11B MAS NMR和27Al MAS NMR光谱均显示出在宿主电气石中峰变宽与过渡金属含量（即Mn2 + + Fe2 + = 0.01–0.30 apfu）的关系。在11B光谱中，[3] B信号的加宽和强度损失最终使对应于[4] B的信号模糊，从而增加了电气石中[4] B的检出限。我们的结果清楚地表明，Si，Al和B的所有组合：T =（Al，Si）6，T =（B，Si）6，T =（Al，B，Si）6，T = Si6 apfu，在天然电气石中很常见

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号