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首页> 外文期刊>Journal of Asian earth sciences >Geochemical patterns of the Akdagmadeni (Yozgat, Central Turkey) fluorite deposits and implications
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Geochemical patterns of the Akdagmadeni (Yozgat, Central Turkey) fluorite deposits and implications

机译：Akdagmadeni（土耳其中部约兹加特）萤石矿床的地球化学特征及其影响

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摘要

Fluorite and fluorite-bearing Pb-Zn-Ag (Cu) deposits are quite common in granitoids and associated skarn formations that are products of Late Cretaceous-Early Paleocene magmatic intrusions into Paleozoic metamorphic rocks of the so called Central Anatolian massif. This study investigates the geochemical features, mainly REE distributions, of fluorites from the Akdagmadeni fluorite and fluorite bearing Pb-Zn-Ag (Cu) deposits. These include the vein type Tad Dere, epidote-skarn hosted Biiyuk$al Tepe and the skarn and granite hosted Akcakisla deposits. The REE contents of these deposits are 20.6-48.5 (x = 36.0), 61.3-149.3 (x = 113.0) and 279.2-4222.4 (x = 1280.0) ppm for the Tad D., Bueyuekcal T. and Akcakisla, respectively. In general, the REE contents are intermediate to high and decrease in abundance with increasing distance from the granitic bodies. The LREE contents are dominantly higher than HREE contents and REE normalized patterns indicate decreasing abundances with increasing atomic number. These indicate that all the fluorites are early stage mineralizations. However, Tb/Ca-Tb/La ratios show distinct differences in the nature of the mineralizing fluids. The high ratios of Akcakisla fluorites are evidence of mineralizing fluids rich in late-stage differentiates from a felsic magma, while intermediate to high ratios of the Buyiikcal T. fluorites are products of late-stage differentiates from hydrothermal fluids. Tad D. fluorites were mineralized under hydrothermal conditions. Decreasing SREE contents in the order of Akcakisla, Bueyuekgal T., and Tad D., and Sc/Eu vs Sr distribution (Sr increases with increasing distance from the magmatic rocks) also supports this order of formation. Each of the three types of fluorite deposits plot in well-defined areas in the Sc/Eu vs Sr diagram. Eu and Ce anomalies give a mixed pattern; the Tad D. fluorites have strong negative Eu anomalies indicating low T and low fo_2 mineralizing fluids. Strong positive Eu anomalies for the Akcakisla fluorites are probably due to high fo_2. The Ce anomalies are strongly negative for the Akcakisla, negative for the Bueyuekcal T. and weakly negative for the Tad D. fluorites. These indicate high fo_2 conditions for the Akcakisla, intermediate for the Bueyuekcal T. and low for the Tad D. fluorites. Because of distinguishable differences in REE patterns, the fluorite deposits plot in well-defined areas in Sc/Eu vs Sr, (La/Yb)_n-(Eu/Eu~*)_n Sr-(Eu/Eu~*)_n, Sc-∑REE, (Tb/Yb)_n-(La/Yb)_n, Tb/Ca-Tb/La diagrams, and indicate different origins and depositional histories. The homogenization temperatures (T_H) range from 156 to 185 ℃ with the corresponding salinities between 12 and 23 wt% NaCl for the Tad Dere ores, 390 to 430 ℃ with the corresponding salinities 8 and 12 wt% NaCl for the Akcakisla and Bueyuekcal Tere ores. Consequently, the field, fluid inclusion data and REE geochemistry indicate that the composition of mineralizing fluids, the locations of ore formations relative to the plutons, the mineralizing mechanisms and the prevailing physicochemical conditions of the depositional environments for the fluorite deposits of Akdagmadeni, were different.
机译：萤石和含萤石的Pb-Zn-Ag（Cu）矿床在花岗岩和相关的矽卡岩岩层中非常普遍，这些岩岩是晚白垩世-早古新世岩浆侵入到所谓的中安纳托利亚地块的古生代变质岩中的产物。本研究调查了Akdagmadeni萤石和含萤石的Pb-Zn-Ag（Cu）矿床中萤石的地球化学特征，主要是REE分布。这些包括脉型的塔德·德雷（Tad Dere），隐伏的矽卡岩型的Biiyuk $ al Tepe以及矽卡岩和花岗岩型的阿克卡奇斯拉矿床。对于Tad D.，Bueyuekcal T.和Akcakisla，这些矿床的REE含量分别为20.6-48.5（x = 36.0），61.3-149.3（x = 113.0）和279.2-4222.4（x = 1280.0）ppm。通常，REE含量处于中高水平，并且随着距花岗岩体距离的增加，丰度降低。 LREE含量显着高于HREE含量，REE归一化模式表明随着原子序数的增加，丰度降低。这些表明所有萤石都是早期矿化。然而，Tb / Ca-Tb / La比值显示出矿化流体性质的明显差异。 Akcakisla萤石的高比率是矿化流体的富集，其特征是与长英质岩浆的后期分化有关，而Buyiikcal T.萤石的中高比率是与热液流体的后期分化的产物。 Tad D.萤石在水热条件下矿化。 SREE含量按Akcakisla，Bueyuekgal T.和Tad D.的顺序减少，Sc / Eu与Sr的分布（Sr随着距岩浆岩距离的增加而增加）也支持这种形成顺序。三种萤石矿床中的每一种均在Sc / Eu与Sr图的明确定义的区域中绘制。 Eu和Ce异常给出了混合的模式。 Tad D.萤石具有强烈的Eu负异常，表明低T和低fo_2矿化液。 Akcakisla萤石的强正Eu异常可能是由于高fo_2引起的。 Ce异常对Akcakisla强烈不利，对Bueyuekcal T.不利，对Tad D.萤石不利。这些表明Akcakisla的fo_2条件较高，Bueyuekcal T.的中间水平，而Tad D.萤石的水平较低。由于REE模式的显着差异，萤石矿床在Sc / Eu与Sr（（La / Yb）_n-（Eu / Eu〜*）_ n Sr-（Eu / Eu〜*）_ n， Sc-∑REE，（Tb / Yb）_n-（La / Yb）_n，Tb / Ca-Tb / La图，并指示不同的成因和沉积历史。 Tad Dere矿石的均质温度（T_H）为156至185℃，相应的盐度为12至23 wt％NaCl； Akcakisla和Bueyuekcal矿石的均质温度为390至430℃，相应的盐度为8至12 wt％NaCl。 。因此，现场，流体包裹体数据和稀土元素地球化学表明，阿克玛德尼萤石矿床的矿化流体组成，矿床相对于云母的位置，矿化机理以及沉积环境的主要理化条件是不同的。 。

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