• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Contributions to Mineralogy and Petrology >Oxidised phase relations of a primitive basalt from Grenada, Lesser Antilles
【24h】

Oxidised phase relations of a primitive basalt from Grenada, Lesser Antilles

机译：格林纳达，小安的列斯群岛的原始玄武岩的氧化相关系

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

A series of liquidus determinations is reported for a primitive arc basalt (15.4 wt %MgO, 45.5 wt %SiO_2) from Grenada, Lesser Antilles, at anhydrous, H_2O-under-saturated and H_2O-saturated conditions in the pressure range 1 atm to 1.7 GPa. Fe~(3+)/ΣFe of high-pressure experimental glasses as measured by μXANES ranges from 0.44 to 0.86, corresponding to oxygen fugacities (fO_2) between 3.2 and 7.8 log units above the nickel-nickel oxide redox buffer (NNO). 1-atm experiments conducted from NNO - 2.5 to + 3.8 show that increasing fO_2 mainly increases the forste-rite content (Fo) of olivine and has little effect on phase relations. The crystallisation sequence at lower crustal pressures for all water contents is forsteritic olivine + Cr-rich spinel followed by clinopyroxene. The anhydrous liquidus is depressed by 100 and 120℃ in the presence of 2.9 and 3.8 wt % H_2O, respectively. H_2O-undersaturated experiments at NNO + 3.2 to + 4.5 produce olivine of equivalent composition to the most primitive olivinephenocrysts in Grenadan picrites (F091.4). We conclude that direct mantle melts originating beneath Grenada could be as oxidised as ~NNO + 3, consistent with the uppermost estimates from olivine-spinel oxybarometry of high Mg basalts. U.XANES analyses of olivine-bearing experimental glasses are used to develop a semi-empirical oxybarometer based on the value of ((K_D)_(ol-melt))~(Fe-Mg) when all Fe is assumed to be in the Fe~(2+) state ((K_D))~(FeT). The oxybarometer is tested on an independent data set and is able to reproduce experimental fO_2 to <1.2 log units. Experiments also show that the geo-chemically and petrographically distinct M- and C-series lavas on the island can be produced from hydrous melting of a common picritic source. Low pressures expand the olivine stability field at the expense of clinopyroxene, enriching an evolving melt in CaO and forcing differentiation to take place along a C-series liquid line of descent. Higher pressure conditions allow early and abundant clinopyroxene crystallisation, rapidly depleting the melt in both CaO and MgO, and thus creating the M-series.
机译：据报道，在无水，H_2O欠饱和和H_2O饱和条件下，压力范围为1 atm至1.7的条件下，来自格林纳达，小安的列斯群岛的原始电弧玄武岩（15.4 wt％MgO，45.5 wt％SiO_2）进行了一系列液相线测定。 GPa。通过μXANES测量的高压实验玻璃的Fe〜（3 +）/ΣFe为0.44至0.86，对应于镍-镍氧化物氧化还原缓冲液（NNO）上方3.2至7.8 log个单位之间的氧逸度（fO_2）。从NNO-2.5到+ 3.8进行的1-atm实验表明，增加fO_2主要是增加橄榄石的橄榄石含量（Fo），而对相关系的影响很小。所有含水量在较低地壳压力下的结晶顺序为镁橄榄石+富铬尖晶石，然后依次为次品。在2.9和3.8 wt％的H_2O存在下，无水液相线分别降低100和120℃。在NNO + 3.2至+ 4.5下进行的H_2O欠饱和实验产生的橄榄石的成分与格林纳达（Grenadan）苦味岩中最原始的橄榄石隐晶（F091.4）相同。我们得出的结论是，格林纳达以下的直接地幔熔体可能被氧化为〜NNO + 3，这与高镁玄武岩的橄榄石-尖晶石透氧法的最高估计值一致。当假设所有的Fe都存在于样品中时，使用含橄榄石的实验玻璃的U.XANES分析基于（（K_D）_（ol-melt））〜（Fe-Mg）的值来开发半经验的氧压计。 Fe〜（2+）状态（（K_D））〜（FeT）。氧压计在独立的数据集上进行了测试，并且能够将实验性fO_2再现为<1.2 log单位。实验还表明，该岛上地球化学和岩石学上不同的M系列和C系列熔岩可以通过常见hydro水源的水溶融化产生。低压扩大了橄榄石的稳定范围，而代价是次氯环己烯，富集了不断演化的CaO熔体，并迫使其沿C系列下降液体线发生分化。较高的压力条件允许早期和大量的次氯环己烯结晶，迅速耗尽CaO和MgO中的熔体，从而形成M系列。

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