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首页> 外文期刊>Contributions to Mineralogy and Petrology >Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal): genetic implications of crystal-chemical and isotopic features
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Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal): genetic implications of crystal-chemical and isotopic features

机译：Penamacor-Monsanto花岗岩岩体和宿主岩中的电气石事件（中部葡萄牙）：晶体化学和同位素特征的遗传意义

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摘要

Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (δ~(18)O, 5D, δ~(11)B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl-oxyschorl tourmalines from granitic rocks have variable foititic component (~X□ = 17-57 %) and Mg/ (Mg + Fe) ratios (0.19-0.50 in two-mica granitic rocks, and 0.05-0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant δ~(18)O values (12.1 ± 0.1 ‰), with wider-ranging δD (-78.2 ± 4.7 %o) and δ~(11)B (-10.7 to -9.0 ‰) values; (b) vein/ breccia oxyschorl [Mg/(Mg + Fe) = 0.31-0.44] results from late, B- and Fe-enriched magma-derived fluids and is characterized by δ~(18)O = 12.4 %o, δD = -29.5 %o, and 8nB = - 9.3‰, while replacement tourmalines have more dravitic compositions [Mg/(Mg + Fe) = 0.26-0.64], close to that of detrital tourmaline in the surrounding metapelitic rocks, and yield relatively constant δ~(18)O values (13.1-13.3 ‰), though wider-ranging 5D (-58.5 to -36.5 ‰) and δ~(11)B (-10.2 to -8.8 ‰) values; and (c) detrital tourmaline in contact rocks and regional host metasediments is mainly dravite [Mg/(Mg + Fe) = 0.35-0.78] and oxydravite [Mg/(Mg + Fe) = 0.51-0.58], respectively. Boron contents of the granitic rocks are low (<650 ppm) compared to the minimum B contents normally required for tourmaline saturation in granitic melts, implying loss of B and other volatiles to the surrounding host-rocks during the late-magmatic stages.
机译：考虑到电气石作为花岗岩岩浆演化的示踪剂和锡-钨矿化的潜在指示物，伊比利亚半岛已广泛记录了与变质质宿主岩中的高铝质花岗岩侵入有关的电气化作用。在Penamacor-Monsanto花岗岩岩体（中东部葡萄牙，伊比利亚中部地区）中，发生电气石：（1）在两云母花岗岩，白云母-花岗岩和and石中为副相，（2）在石英（±云母）-电气石中几个接触点处的岩石（旅辉石），和（3）在接触带角f和变质宿主岩中为罕见的碎屑相。电子微探针和稳定同位素（δ〜（18）O，5D，δ〜（11）B）数据在这些不同背景下的电气石种群之间提供了明显的区别：（a）花岗岩岩石中的松香-氧松香电气石具有可变的成因成分（〜 X□= 17-57％）和Mg /（Mg + Fe）比率（两云母花岗岩中为0.19-0.50，而分化程度更高的白云母-花岗岩中则为0.05-0.19）;花岗岩电气石具有恒定的δ〜（18）O值（12.1±0.1‰），范围更广的δD（-78.2±4.7％o）和δ〜（11）B值（-10.7至-9.0‰）; （b）静脉/角砾岩[Mg /（Mg + Fe）= 0.31-0.44]是来自后期富含B和Fe的岩浆衍生流体的结果，其特征在于δ〜（18）O = 12.4％o，δD = -29.5％o，且8nB =-9.3‰，而替代电气石具有更多的蠕变成分[Mg /（Mg + Fe）= 0.26-0.64]，与周围变质岩中的碎屑电气石接近，并且产量相对恒定δ〜（18）O值（13.1-13.3‰），尽管5D（-58.5至-36.5‰）和δ〜（11）B（-10.2至-8.8‰）值范围更广; （c）接触岩和区域性主体沉积物中的碎屑电气石主要是德拉瓦特[Mg /（Mg + Fe）= 0.35-0.78]和氧化钠[Mg /（Mg + Fe）= 0.51-0.58]。与花岗岩熔体中电气石饱和通常所需的最低B含量相比，花岗岩岩石中的硼含量低（<650 ppm），这意味着在岩浆后期，B和其他挥发物会流失到周围的主体岩石中。

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