斯洛伐克西喀尔巴阡山脉内侧Veporicum地区的地球动力学演化序列与菱镁矿和滑石矿床成因

本文总结并报导了斯洛伐克西喀尔巴阡山脉内侧的石炭纪岩石中产出的菱镁矿和滑石成因的最新资料.这些矿床赋存于Veporicum构造超单元中和该超单元与Gemericum的接触带中.北部Sinec成矿带是主要的菱镁矿和滑石矿化区,产出的主要矿床有Kokava,Sinec,Samo,Hnsta-Mutnik等矿床.而南部的Ochtina成矿带只产有菱镁矿床,主要矿床包括在Dubrava地体上的Dubrava,Mikov?JedL'vec;Luben韐,Ochtina,Kosice-Bankov,Banisko,Medvedia等矿床.菱镁矿形成于变质M1期石炭系中方解石被白云石和菱镁矿连续交代过程(北矿带成矿温度为280～400℃,南矿带成矿温度为370～420℃;Radvanec＆Prochska,2001;Kodera＆Radvanec,2002).Permoscythian蒸发卤水提供了Mg.成矿事件和华力西期碰撞后运动有关.拉伸构造和高热流值促使成矿热液系统的产生.滑石矿化则形成于稍晚的不同期变质事件(M2),成矿流体来源也与菱镁矿化不同.构造的、微构造的、变质的以及地质年代学的数据将滑石成矿作用和阿尔卑斯上白垩系的构造地热事件AD2联系在一起.AD2事件是阿尔卑斯碰撞(AD1)地壳加厚和变质核杂岩体起源的结果,体现在地壳不整合面上的区域拉伸,及开放系统中大规模热液流动.这一过程在更靠近Veporic热穹的北带区域(Sinec剪切带)很显著,而向着Veporic热穹的周围部分(南Ochtina带),M2变质过程和块滑石化则逐渐减弱.Sinec剪切带是北Sinec带中突出的AD2-AD3结构,白云石/菱镁矿透镜体(在M1期交代造成的)和相伴随的岩石夹杂在AD1中更坚硬的基底岩石之中.本研究证明了AD2中块滑石化的普遍性,滑石和白云石2形成于拉伸显微构造中(变质过程M2;温度为490～540℃,压力为240～330MPa).在Sinec带中AD3阶段的对偶剪切作用形成了该带中的滑石矿.它是AD2事件从去顶到区域扭压剪切的动力学转变过程的逐步延续.北Sinec带使AD3变形处于由坚硬岩石包围的软岩石的狭窄的剪切带中,而在南Ochtina带中AD3变形产生在由里面漂浮着坚硬碳酸盐块的软的岩石柱中.在Ochtina带中,在AD2和AD3阶段由于M2期较低的P-T条件和变形梯度导致了该区有经济价值的滑石矿化不发育.总之,现有的研究结果能用作阿尔卑斯型地体中菱镁矿和滑石找矿的基本标志.

Magnesite and talcorigin in the sequence of geodynamic events in Veporicum, Inner Western Carpathians,Slovakia

This paper summarizes recent data about magnesite and talc genesis in Carboniferous host rocks of Western Carpathians (Slovakia), which occur in two distinct belts in tectonic superunit Veporicum and its contact zone with Gemericum. The northern Since magnesite and talc belt (with main deposits Kokava, Sinec, Samo, Hnust'a-Mutnik) contains economic accummulation of magnesite Kosice - Bankov, Banisko, Medvedia) the magnesite is dominating.The magnesite genesis by successive replacement of Carboniferous calcite to dolomite and magnesite during metamorphic process M1 (northern belt 280 ～ 400℃, southern belt 370 ～ 420℃; Radvanec & Prochaska, 2001; Kodera & Radvanec, 2002), being supplied by Mg from Permoscythian evaporitic bittern brines, relates to Variscan post-collisional (post-VD) evolution. The extensional tectonics and the high heat flow facilitated the generation of a hydrothermal system.The time-separated later metamorphic and sourcely different fluid flow event (M2; l. C.) produced talc. Tectonic, microtectonic,al., 1996) tectonothermal event AD2. This event, being the consequence of Alpine collisional (AD1) crustal thickening and metamorphic core complex origin, meant regional extension and pervasive fluid flow of open system in crustal discontinuities. This process was prominent in the northern belt (Sinec shear zone) located more closely to Veporic thermal dome, while towards its peripheral parts (southern Ochtina belt) the M2 metamorphic process and steatitization gradually weakened.Studies from Sinec shear zone (being the prominent AD2-AD3 structure of northern Sinec belt), where the dolomite/magnesite lenses (replacement in M1) and their accompanying lithology were in AD1 sandwitched between more competent basement blocks,proved in AD2 the pervasite steatitization, the talc and dolomite 2 origin in extensional microstrnctures (metamorphic process M2; 490～540℃, 240 ～330 Mpa, l. C.).The economic accummulations of talc in Sinec belt are the products of antithetic shearing during the AD3 phase, being the gradual continuation of AD2 (change of kinematics from unroofing to regional transpressional shearing). Contrary to the northern Sinec belt having located the AD3 deformation into narrow shear zone with soft lithology surrounded by hard lithology, in southern Ochtina belt the deformation AD3 was accommodated by wide soft rock column with rigid carbonate blocks floating inside. The lower P-T (M2) conditions and deformational gradient in Ochtina belt during AD2 and AD3 phases caused why no economic talc accummulations developed there. The results of presented study can be used as general criteria for magnesite and talc prospection in Alpine type terranes.