Microlite-group minerals: tracers of complex post-magmatic evolution in beryl-columbite granitic pegmatites, Maršíkov District, Bohemian Massif, Czech Republic

2021 ◽  
pp. 1-55
Author(s):  
Štěpán Chládek ◽  
Pavel Uher ◽  
Milan Novák ◽  
Peter Bačík ◽  
Tomáš Opletal
2020 ◽  
Vol 28 (1) ◽  
pp. 132-151 ◽  
Author(s):  
Zdeněk Dolníček ◽  
Karel Malý ◽  
Jana Ulmanová ◽  
Jaroslav Havlíček ◽  
Luboš Vrtiška

In the Pohled quarry near Havlíčkův Brod town (central part of Czech Republic), granitic pegmatites form dikes or irregular bodies cementing breccia of host metamorphic rocks (paragneisses, amphibolites) belonging to the Monotonous (Ostrong) Group of the Moldanubicum of the Bohemian Massif. Pegmatites exhibit coarse-grained textures and very simple mineral composition, which, however, was in places strongly modified by superimposed hydrothermal alterations and locally also by crystallization of ore minerals. K-feldspar, plagioclase (An0-38), biotite (phlogopite), apatite (fluorapatite to hydroxylapatite), zircon, allanite-(Ce) and part of quartz undoubtedly originated during magmatic stage. Products of hydrothermal alterations include younger quartz, Fe-Mg chlorites (older clinochlore and younger chamosite with an admixture of Ca-smectite), prehnite, clinozoisite, amphibole (actinolite), titanite, calcite, and very probably also ilmenite (with up to 22.5 mol. % of pyrophanite), rutile, anatase and V-Cr-Fe-rich grossular with 13 - 25 mol.% of goldmanite and 12 - 24 mol.% uvarovite. The elevated contents of Mg, Ca, V and Cr found in some minerals are associated with a material contamination by the surrounding metamorphic rocks (especially amphibolites, serpentinites and perhaps also graphitic lithologies), which took place with varying intensity during both magmatic and hydrothermal stages of evolution of the studied pegmatites. Geochemically, they are poorly fractionated pegmatites, whose origin was probably connected with anatexis of the host Moldanubian metamorphic rocks, which was likely associated with emplacement of adjacent small body of the Pohled Granodiorite.


2014 ◽  
Vol 64 (4) ◽  
pp. 367-392 ◽  
Author(s):  
Karolína Lajblová ◽  
Petr Kraft

Abstract The earliest ostracods from the Bohemian Massif (Central European Variscides) have been recorded from the Middle Ordovician of the Prague Basin (Barrandian area), in the upper Klabava Formation, and became an abundant component of fossil assemblages in the overlying Šarka Formation. Both early ostracod associations consist of eight species in total, representing mainly eridostracans, palaeocopids, and binodicopids. The revision, description, or redescription of all species and their distribution in the basin is provided. Their diversification patterns and palaeogeographical relationships to ostracod assemblages from other regions are discussed.


The Holocene ◽  
2021 ◽  
pp. 095968362110116
Author(s):  
Lucie Juřičková ◽  
Jakub Menšík ◽  
Jitka Horáčková ◽  
Vojen Ložek

The Alps are an important hotspot of species diversity and endemism, as well as a presumed glacial refugium of several species’ groups including land snails. The recent ranges of Alpine endemics are well known, but their fluctuations during the postglacial period mirroring local climate changes are understudied. By analysing five Late Glacial and Holocene mollusc successions from two areas in the southernmost part of the Bohemian Massif (Czech Republic) situated about 100 km north of the Alps, we reveal details of these fluctuations. The Alpine endemic rocky dweller Chilostoma achates had reached the southern part of the Bohemian Massif already in the Late Glacial and disappeared in the Mid-Holocene canopy forest optimum. On the contrary, the northern boundaries of Alpine canopy forest epigeic snails extended further north than today at the turn of the Middle and Late-Holocene, pointing to a more favourable forest microclimate. The earliest known occurrences of several temperate canopy forest central European species, especially Causa holosericea and Discus perspectivus, imply the role of different areas in the Alps as their glacial refugia.


Author(s):  
Lukáš Krmíček ◽  
Jaromír Ulrych ◽  
Emil Jelínek ◽  
Roman Skála ◽  
Simona Krmíčková ◽  
...  

2021 ◽  
Vol 77 (2) ◽  
pp. 282-286
Author(s):  
Jiří Kvaček

A specimen of Araucaria fricii is described from the upper part of the Teplice Formation in the Bohemian Cretaceous Basin. It extends the first occurrence of A. fricii from the mid-Coniacian back to the early Coniacian. Found in the Radovesice locality near Kučlín in the northern part of the Czech Republic, it is characterised by a deltoid cone scale complex with a centrally placed seed. It is compared to the type material of A. fricii from the mid-Coniacian Březno Formation and other European Cretaceous species of Araucaria. The taphonomy and palaeoecology of A. fricii is briefly discussed.


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