The distribution of halogens (F, Cl, Br) in granitoid rocks
The distribution of halogens (F, Cl, Br) in granitoid rocks
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DOI：
10.1016/j.chemgeo.2014.03.006
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发表时间：
2014-05
期刊：
影响因子：
3.9
通讯作者：
Holger Teiber;M. Marks;T. Wenzel;W. Siebel;R. Altherr;G. Markl
中科院分区：
文献类型：
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作者：
Holger Teiber;M. Marks;T. Wenzel;W. Siebel;R. Altherr;G. Markl
详细研究了波希米亚山脉德国部分和希腊爱琴海中部两个不同地区花岗岩类岩石的卤素含量及其在磷灰石、黑云母、白云母和角闪石之间的分布。全岩F、Cl含量及F/Cl质量比随岩浆岩含卤素矿物组合而有系统变化，所有岩样均含有黑云母和磷灰石；含白云母花岗岩富F（多为1100 ~ 2000 μg，可达3100 μg），相对贫Cl （50 ~ 130 μg）。含角闪岩Cl含量较高（50 ~ 900 μg/g）， f含量相对较差（500 ~ 1400 μg/g）。只有含黑云母和磷灰石的花岗岩中F （750 ~ 1100 μg）和Cl （120 ~ 350 μg/g）含量居中。所有岩石样品的溴含量均低于约0.6 μg/g的检出限。一般来说，氟和氯优先与磷灰石结合，而不是黑云母，黑云母通常比白云母含有更多的氟和氯。同样，黑云母比角闪孔更倾向于F，但不同岩石样品中黑云母和角闪孔之间的Cl分布有所不同。白云母中溴含量低于0.4 μg/g的检出限，黑云母中溴含量可达0.8 μg/g，磷灰石和角闪石中溴含量可达2.5 μg/g。流体溶出、扩散再平衡和热液叠印等近固相效应可能改变岩石中卤素的初始分布。重要的是，整个岩石的大量F（高达60%）和Cl（高达90%）可能被容纳在岩浆后蚀变相（萤石和含na - k - ca的硅酸片）和流体包裹体中。因此，在解释整个岩石的卤素含量时必须非常小心，并考虑后岩浆期卤素载体的影响。
The halogen contents of granitoid rocks and their distribution between apatite, biotite, muscovite and amphibole from two different localities (German part of the Bohemian Massif and Central Aegean, Greece) are investigated in detail. Whole rock F and Cl contents and F/Cl mass ratios vary systematically with the magmatic halogen-bearing mineral assemblage in which biotite and apatite are present in all rock samples: muscovite-bearing granites are F-rich (mostly 1100–2000 μg/g, but up to 3100 μg/g) and are relatively Cl-poor (50–130 μg/g). In contrast, amphibole-bearing rocks reach high Cl contents (50–900 μg/g) and are relatively F-poor (500–1400 μg/g). Only biotite- and apatite-bearing granites show intermediate F (750–1100 μg/g) and Cl (120–350 μg/g) contents. Bromine contents of all rock samples are below the detection limit of about 0.6 μg/g.In general, F and Cl are preferentially incorporated in apatite over biotite and biotite usually contains higher amounts of F and Cl than muscovite. Similarly, biotite prefers F over amphibole, but the distribution of Cl between biotite and amphibole varies between different rock samples. Bromine contents in muscovite are below the detection limit of 0.4 μg/g, but can reach up to 0.8 μg/g in biotite and up to 2.5 μg/g in apatite and amphibole.Near-solidus effects such as fluid exsolution, diffusive re-equilibration and hydrothermal overprint may change the initial halogen distribution in the rock. Importantly, significant amounts of the whole rock's F (up to 60%) and Cl (up to 90%) may be accommodated in post-magmatic alteration phases (fluorite and Na–K–Ca-bearing sheet silicates) and fluid inclusions. Therefore, great care has to be taken when interpreting halogen contents of whole rocks and the influence of post-magmatic halogen-carriers needs to be taken into account.