Changes in tourmaline composition during magmatic and hydrothermal processes leading to tin-ore deposition: The Cornubian Batholith, SW England
Changes in tourmaline composition during magmatic and hydrothermal processes leading to tin-ore deposition: The Cornubian Batholith, SW England
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DOI：
10.1016/j.oregeorev.2016.11.012
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发表时间：
2017-04
影响因子：
3.3
通讯作者：
Marguerita Duchoslav;M. Marks;K. Drost;C. McCammon;H. Marschall;T. Wenzel;G. Markl
中科院分区：
文献类型：
--
作者：
Marguerita Duchoslav;M. Marks;K. Drost;C. McCammon;H. Marschall;T. Wenzel;G. Markl
为了研究电气石作为地球化学监测剂的潜力，提供了电气石主要、微量和微量元素浓度以及 Fe3+/ΣFe 比率的综合数据集。该数据集包括来自与 Cornubian Batholith（英格兰西南部）不同岩浆到热液阶段相关的五个深成杂岩体的样本。在贫瘠和含锡石样品中发现的电气石成分包括所有三个主要电气石族和电气石种类，其一般端元为黄铁矿、镁镁铁矿、钠锂辉石、钙镁矿、铁镁矿、钙铁矿和镁钙铁矿。根据结构和成分，不仅可以区分晚期岩浆和热液电气石，还可以区分几个形成阶段。因此，电气石监测晚期岩浆过程和水相溶出过程中元素的分配。例如，与同一样品的晚岩浆电气石相比，在热液电气石中，Sn 被强烈富集，而 Ti、Cr、V 和 Sc 则被贫化。从岩浆液中沉淀出来的几代碧玺可以通过不同的主要和微量元素以及稀土元素模式来区分，具体取决于它们所排出的熔体的成分。强烈分区的碧玺可以揭示特定位置的热液历史，包括矿石沉淀。研究区SnO2的沉淀可能是由酸性、还原性、含锡岩浆液与氧化性大气流体混合引起的，这与London和Manning(1995)以及Williamson等人的观点一致。 （2000）。因此，电气石成分监测热液中锡浓度和氧化还原条件变化的能力具有作为勘探工具的潜力。
To investigate the potential of tourmaline as a geochemical monitor, a comprehensive dataset on major, minor and trace element concentrations as well as Fe3+/ΣFe ratios of tourmaline is presented. The dataset includes samples from five plutonic complexes related to diverse magmatic to hydrothermal stages of the Cornubian Batholith (SW England). Tourmaline composition found in barren and cassiterite-bearing samples include all three primary tourmaline groups and tourmaline species with the general endmembers schorl, dravite, elbaite, uvite, feruvite, foitite and Mg-foitite.Based on textures and compositions, it is possible to distinguish not only between late-magmatic and hydrothermal tourmaline, but also between several formation stages. Hence, tourmaline monitors late-magmatic processes and the partitioning of elements during exsolution of an aqueous phase. For example, in hydrothermal tourmaline Sn is strongly enriched, while Ti, Cr, V and Sc are depleted compared to late-magmatic tourmaline of the same sample. Several tourmaline generations that precipitated from magmatic fluids can be distinguished with differing major and minor elements and REE patterns depending on the composition of the melt from which they were expelled from. Strongly zoned tourmaline allows for unraveling the hydrothermal history of a distinct location including ore precipitation. The precipitation of SnO2in the study area was probably caused by mixing between acidic, reduced, Sn-bearing magmatic fluids and oxidized meteoric fluids, which is in agreement with London and Manning (1995) and Williamson et al. (2000). Hence, the ability of tourmaline composition to monitor changes in Sn concentration and redox conditions in hydrothermal fluids has potential as an exploration tool.