...
  • 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 >Copper isotope behavior during extreme magma differentiation and degassing: a case study on Laacher See phonolite tephra (East Eifel, Germany)
【24h】

Copper isotope behavior during extreme magma differentiation and degassing: a case study on Laacher See phonolite tephra (East Eifel, Germany)

机译：极端岩浆分化和除气过程中的铜同位素行为：以Laacher See phonophite tephra为例（德国东埃菲尔）

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

Copper (Cu) isotopic analyses were performed on a set of samples from the Laacher See tephra (LST) (Eifel, Germany) to investigate whether Cu isotopes are fractionated during extreme magma differentiation and degassing. The LST represents a continuous fractional crystallization series from parental basanite through mafic to highly differentiated phonolites. Samples analyzed here include phonolites of variable degrees of differentiation, phonolite-basanite hybrid rocks formed by mixing basanite and phonolite magmas, and basanite-derived mega-crystals (i.e., clinopyroxene, amphibole, phlogopite). In addition, we analyzed a series of mafic parental lavas from surrounding volcanic centers to constrain the Cu isotopic features of the Eifel mantle. Mafic phonolites show strong depletion in Cu compared to their parental basanites from similar to 50 to similar to 3 ppm, indicating sulfide fractionation during the basanite-to-phonolite differentiation. Mass balance calculations, based on the most Cu-rich hybrid rock (delta Cu-65 = -0.21 parts per thousand, [Cu] = 46.2 ppm), show that the parental basanite magmas have delta Cu-65 of ca. -0.21 parts per thousand lighter than those of the mafic phonolites (similar to 0.11 parts per thousand This suggests that sulfide fractionation preferentially removes the lighter Cu isotope (Cu-63) in S-saturated magmas. By contrast, all phonolites have a limited range of Cu contents (1.1 to 4.0 ppm) with no systematic variations with S, suggesting that Cu is not controlled by sulfide fractionation during the evolution of mafic to highly differentiated phonolites. The identical delta Cu-65 values (0.11 +/- 0.03 parts per thousand, 2SD, n = 10) of the phonolites, irrespective of highly diverse composition and extents of differentiation, indicate that fractional crystallization of silicates (e.g., plagioclase, sanidine, amphibole, pyroxene, olivine), Fe-Ti-oxides and phosphate (e.g., apatite) generates insignificant Cu isotope fractionation. The lack of correlations between delta Cu-65 and volatile contents (e.g., S, Cl) in the LST sequence implies that volcanic degassing causes no detectable Cu isotope fractionation of igneous rocks. Eifel basalts and mega-crystals have variable delta Cu-65 (-0.18 to 0.21 %) that are uncorrelated to MgO and Cu, suggesting that such variations were not caused by differentiation but reflect the Cu isotopic heterogeneity of the Eifel mantle source due to metasomatism by fluids derived from hydrothermally altered oceanic lithosphere.
机译：对Laacher See tephra（LST）（德国埃菲尔）的一组样品进行了铜（Cu）同位素分析，以研究在极端岩浆分化和除气过程中是否分离了铜同位素。 LST代表了从母体重钙铁矿到镁铁矿再到高分化声石的连续分级结晶系列。这里分析的样品包括不同分化程度的方沸石，通过混合玄武岩和方沸石岩浆形成的方沸石-玄武岩杂化岩，以及源自玄武岩的巨型晶体（即斜辉石，角闪石，金云母）。此外，我们分析了来自周围火山中心的一系列镁铁质亲本熔岩，以约束埃菲尔地幔的铜同位素特征。镁铁质辉石岩与其母质玄武岩相比，其Cu含量从大约50 ppm到3 ppm显着增加，表明在玄武岩向方沸石的分化过程中硫化物的分馏。根据最富Cu的杂化岩（δCu-65 = -0.21千分之一，[Cu] = 46.2 ppm）进行的质量平衡计算表明，母体玄武岩岩浆的δCu-65约为10。比镁铁质方沸石轻-0.21千分之几（类似于0.11千分之一）。这表明硫化物分级法优先去除了S饱和岩浆中较轻的Cu同位素（Cu-63）。相比之下，所有的方沸石都具有有限的范围的铜含量（1.1至4.0 ppm）与S没有系统性变化，这表明从铁铁矿到高分化的方沸石演化过程中，铜不受硫化物分级控制，相同的δCu-65值（每单位0.11 +/- 0.03份）千，2SD，n = 10），不论高度不同的组成和分化程度，都表明硅酸盐（例如斜长石，山san，闪石，辉石，橄榄石），Fe-Ti-氧化物和磷酸盐（例如LST序列中δ-Cu-65与挥发物含量（例如，S，Cl）之间缺乏相关性，这意味着火山脱气不会导致稳定的火成岩铜同位素分馏。埃菲尔玄武岩和巨型晶体具有可变的δCu-65（-0.18至0.21％），与MgO和Cu不相关，这表明这种变化不是由于分化引起的，而是反映了由于交代作用而使埃菲尔地幔源的铜同位素异质性由热液改变的海洋岩石圈中产生的流体引起。

著录项

相似文献

  • 外文文献
  • 中文文献
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