Acta Geodyn. Geomater., Vol. 7, No. 2 (158), 167–174, 2010

DETAILED BRITTLE TECTONIC ANALYSIS OF THE LIMESTONES IN THE QUARRIES NEAR VÁPENNÁ VILLAGE (CASE STUDY)

Lucie NOVÁKOVÁ

Institute of Rock Structure and Mechanics, Academy of Sciences of the Czech Republic, v.v.i., V Holešovičkách 41, 182 09 Prague, Czech Republic Corresponding author‘s e-mail: lucie.novakova@irsm.cas.cz (Received March 2009, accepted February 2010) ABSTRACT This paper describes limestone body situated in the northern part of the Branná group near Vápenná village in Javorník area.The body is confined by two major tectonic zones of this area – Sudetic Marginal Fault on the east and Ramzová overthruston the south. Detailed tectonic analysis has been performed in two big limestone quarries named quarry I and II. Strikes anddips of fault planes and joints were measured. In the quarry I just one important orientation of the fault planes was found – W-E mostly vertical. In the quarry II two main fault plane orientations were observed – vertical NW-SE Sudetic and NE-SWMoravo-Silesian. The senses of movements in the fault planes were determined using the calcite steps mainly as the kinematicindicators. Presence of the kinematic indicators allowed performing of paleostress analysis. Several different tectonic phaseswere identified and discussed. KEYWORDS: brittle tectonics, paleostress analysis, limestone, quarry, Branná group

(2008) stated neotectonic dextral transpression on the Sudetic Marginal Fault zone. Schenk and Schenková (2006) presented recent sinistral movements along the Moravo-Silesian faults and both sinistral and dextral movements along the Sudetic tectonic zones. Despite a number of previous mentioned detailed and other field studies (e.g. Opletal and Pecina, 2004; Skácel, 2004; Štěpančíková, 2005; Nováková, 2008) the precise conditions of reactivation and tectonic development in the studied area are not apparent yet. The aim of this case study was to bring up the detail view of the structure of the limestone body and to discuss the previously mapped fault zones in the studied area.

2. GEOGRAPHICAL AND GEOLOGICAL

SETTINGS The deposit of the limestones is located close to

a railway station about 500 meters westward of the village Vápenná (Fig. 1) about 10 kilometres to NW from the Jeseník town. The mountainous area belongs to the Rychleby Mountains. The altitude here varies from 430 up to 520 metres above see level. The river Vidnávka runs through the NE part of the deposit. The limestone body is intersected by the Lost (Ztracený) creek valley. The deposit was exploited in several separated quarries. North of the Lost creek there are two big quarries (quarry I and II) where this case study was performed.

The limestones belong to the northern ending of the Branná rock group of the Devonian age. On the

1. INTRODUCTION Limestone as a nonmetalliferous raw material

has been important in the Javorník area since 18th

century. Exploitation of the limestone deposit beganbefore 1787 when the limestone was fired in thespecial furnaces. In 1869 A. Latzel made up the firstcircled furnace. In this time some quarries werenamed after landlords - Neugebauer, Rosener andLatzel. From 1955 to 1958 detailed geologicalresearch for possible exploitation of the deposit wasdone. Limestone was exploited mainly for productionof lime, glass, cellulose, soda and mineral fertilizer.The lime has been used for the rendering in the streetsin many European cities e.g. Paris, Berlin or Vienna(Vocilka, 1958).

From the tectonic point of view the limestonebody of the Branná group is very important. It belongs to a Moravosilesian zone that is unique due tosuperposition of three structural levels – Cadomian, Variscan and Alpine (Jelínek, 2004). Schulmann andGayer (2000) described the structural development ofthe northeastern margin of the Bohemian Massif from Devonian rifting to Late Carboniferous transpression.Grygar and Jelínek (2000) suggested the fault zones ofNW-SE and NNW-SSE (the Sudetic) directions weredistinctively rejuvenated by the Alpine orogenesis.Within context of the late Variscan and post Variscantectonics the most important zone is the Moravo-Silesian NNE-SSW zone (Grygar, 2004). Schenk et al.(2004) related neotectonic activity to the WNW-ESE and NW-SE striking fault zones. Štěpančíková et al.

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Fig. 1 Tectonic situation of the limestone body in the northernpart of the Branná group and the approximate positions ofthe quarry I (Q1) and the quarry II (Q2). Symbols: SMF-Sudetic Marginal Fault, RO-Ramzová overthrust, MF-main faults, SF-secondary faults. Modified after Žáček et al.(1995) and Skácel (2004).

occurrence of Mg might be explained by presence of granite plutonic rocks on the NE. An activity of this pluton probably caused movements of the rocks of the Branná group in the NW direction. Thrusting rocks of the Branná group took their actual place above biotite paragneisses in the WNW-ESE direction during this pressure caused movements. The thrust zone is the south zone of confinement of the northern part of the Branná group (Vocilka, 1958). Skácel (2004) denoted the Nýznerov fault zone a W tectonic border of the limestone body.

The quarry I (Fig. 2) is situated in the southern part of the north part of the Branná group. This quarry was called Neugebauer earlier (Vocilka, 1958). The quarry is about 1000 meters long and on about 200 meters wide.

The quarry II (Fig. 3) is situated in the northern part of the north body of the Branná group. This quarry was called Latzel (Vocilka, 1958). The quarry is about 1500 meters long and averagely 300 meters wide. There are two or three levels in each quarry. Maximum high of the quarry face is about 80 meters. Limestones are slightly karsified. It is possible to find up to 3 cm crystals of calcite there.

west, the group starts on the Bušín fault zone andcontinues eastwards to its end on the Sudetic MaginalFault in the Vápenná village. Despite the southernborder of the Branná group is clearly bounded to anoverthrust, the eastern border is not clear yet.However Vocilka (1958) named this fault zone Polkaovethrust, Skácel (2004) put there Ramzováoverthrust.

The rocks of the Branná group are possible todivide into four characteristic groups of strata. Highlydeformated paragneisses and biotitic-gneisses formthe first one. The second strata consist of siliceousgraphitic slates sometimes with the 0.5 m thickgraphitic layers. Crystalline black or grey limestonesfollow the slates. Up to 5 m width limestone layercontains mass of graphitic pigment and frequentlypyrite. Finally, the last strata comprise slightlycrystalline limestones of white to grey colour. Theselimestones make up 5-10 m thick layer.

3. QUARRY I AND II

The limestone quarries have been excavated inthe strata of white to grey rough crystallinelimestones. Above this strata there are light limestonescharacterised by strikes often with dolomite. An

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Fig. 2 Panoramic view of the second level in the quarry I.

Fig. 3 Panoramic view of the quarry II.

quarry II appear to be rotated about 15 degrees anticlockwise to the fracture system in the quarry I.

Nováková (2008) mentioned three sets of faults in the limestones – the NW-SE fault set, the N-S set and especially the W-E set. The detailed analysis in the quarries confirmed this finding. The contour diagrams of poles to faults (Figs. 5a, b) identify the fault planes in the studied quarries. The W-E orientation of the fault planes is the only important in the quarry I. The planes are vertical mostly (Fig. 5a). Two main directions, subvertical NW-SE and subvertical ENE-WSW, dominate in the quarry II (Fig. 5b). Only 19 % of the fracture planes in the quarry I and 7 % in the quarry II display some kinematic indicator proving a movement and therefore approving their fault status. Despite wide range of fractures in both quarries, most of the fault planes are subvertical. The W-E orientation of fault planes dominates in the quarry I while the NW-SE and NE-SW orientations in the quarry II.

The difference in fracturing (and faulting) among the quarries suggests difference in either external or internal conditions. Thus two parts of the limestone body represented by two studied quarries might be for example exposed to different stresses or one of them was rotated.

Distribution of fault planes with senses of the movements was displayed into the schematic map of

Twenty two partial small localities around thequarry face in the quarry I were chosen and described.Twenty five partial localities were picked up in thequarry II. The strikes and dips of the fault planes andjoints were measured. The senses of movements in these fault planes were determined using the calcitesteps.

4. RESULTS AND DISCUSSION

The crystalline limestone body is fracturedintensively in both quarries. The movement along theplane of fracture is usually demonstrated by presenceof some kind of the kinematic indicator (calcitesteps, slickenlines, stylolites, etc.). The fault planesand kinematic indicators data were processed anddisplayed using Daisy (Figs. 4, 5), Tectonics FP (Figs. 6, 7) and T-Tecto (Figs. 8, 9) software.

Four main orientations of fractures wereidentified in the limestone body (Figs. 4a, b). Themost frequent are subvertical W-E fractures, subvertical NW-SE (the Sudetic direction), subverticalN-S fractures and subhorizontal fractures. Howeveranalogically oriented fractures might be found in bothquarries, the fracture systems assign a rather distinctcharacter. The horizontal fractures and vertical N-S or E-W fractures are frequent in the quarry I (Fig. 4a),but almost absent in the quarry II (Fig. 4b). If it is not for the SW dipping NW-SE fractures, the fractures in

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b a

Fig. 4 Contour diagrams of poles to fracture planes. Contouring interval 1 %. a) quarry I, n=957, b) quarry II, n=923.

b a

Fig. 5 Contour diagrams of poles to fault planes. Contouring interval 2 %. a) quarry I, n=186, b) quarry II, n=63.

Analysis of the kinematic indicators was

performed on the data sets for both quarries separately using T-Tecto software (Žalohar, 2008). The Gauss methods was applied (Žalohar and Vrabec, 2007). Gauss paleostress method identified four various phases in the quarry I (Figs. 8, A-D) and four in the quarry II (Figs. 9, A-C, E). Main orientations of σ1 (maximal stress) and σ3 (minimal stress) axis were computed for each tectonic event. Obtained paleostress axes are displayed in the stereograms as squares where the biggest represents σ1 and the smallest σ3.

In the quarry I the most fault planes (n=76) occur in the phase D (Fig. 8D). The maximal compression is in the NE-SW direction, while the extension is NW-SE. The second most delegated phase is A (Fig. 8A,

the quarry I (Fig. 6) and II (Fig. 7). Amount of faultorientations in the limestones points to the developedtectonics in the limestone body. Huge number ofkinematic indicators, calcite steps mainly, wasobserved on fault planes in both quarries. Because ofthe heterogeneity of the data it was necessary to dividethe faults into the separate phases. However several fault planes provided two different sets of thekinematic indicators the time relations of the tectonicphases were not possible to clearly determine.Nevertheless the observed presence of differentlyoriented kinematic indicators in the very same plane isundoubtedly an evidence of different movementsalong the plane. Two or more movements along onefault plane apparently point to the reactivation of thefault.

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Fig. 6 Quarry I. Stereograms of fault planes with arrows indicating the senses of movements.Lambert projection, lower hemisphere.

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Fig. 7 Quarry II. Stereograms of fault planes with arrows indicating the senses of movements. Lambert projection, lower hemisphere.

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Fig. 8 Four different tectonic regimes in the quarry I calculated by T-Tecto 2.0 software.

Fig. 9 Four different tectonic regimes in the quarry II calculated by T-Tecto 2.0 software.

planes support the hypothesis. However the phases in both quarries are clear, the time sequence of the phases was not possible to determine accurately.

Vocilka (1958) described few lateral fault zones in NW-SE direction with thrust character in the limestone body. Žáček (1995) confirmed several parallel fault zones in the NNW-SSE up to NW-SE directions (see Fig. 1). Pressures during the thrusting probably caused the limestone body slightly rotate. The rotation might explain the different fracturing and faulting in the quarries.

Grygar and Vávro (1995) documented the dextral late-Variscan and Post-Variscan strike-slip kinematics along the Sudetic WNW trending. The phases C (Figs. 8, 9 C) might be connected with this period. Grygar (1991) also claimed the maximal compression in NW-SE direction during Variscan orogenesis. While phases B (Figs. 8, 9 B) correspond this statement, the time sequence of the phases B and C is not apparent. It may be also possible the younger tectonic movements get on the older fractures and caused reactivation on them. This idea is supported by Jelínek (2004), who described role of the Alpine rejuvenation of the Variscan fault structures of faults N-S to NNE-SSW (originally Variscan) but mainly of faults in W-E direction. Pešková et al. (2008) found two phases of movements in the limestone body. One of these phases corresponds to phases B. In the case of limestone body three sets of fractures (W-E, NW-SE, N-S) were reactivated apparently.

n=60), where the maximal extension analyses NE-SW direction and compression is almost vertical. Theother two phases have similar amount of faults, butdifferent orientations of stresses. Phase B (Fig. 8B,n=12) shows maximal compression in WNW-ESE direction and less significant extension in NE-SW direction. The last phase delegated the least faults (Fig. 8C, n=8) has the same dimension of the S-N compression and W-E extension.

In the quarry II the most fault planes belong tothe phase A (Fig. 9A, n=27). There are two extensionsin N-S and W-E directions while the compression isvertical. The second most frequent is the phase E(Fig. 9E, n=18) which seems to be parallel to thephase D (Fig. 8D) in the quarry II. Although σ1 has different orientation, the directions of compressionand extension are more or less similar. The phases B(Fig. 9B, n=9) and C (Fig. 9C, n=6) have very similarorientation of σ1 and almost same directions ofcompressions and extensions.

When phases in both quarries compared three ofthem seem to be very same (the phase A intranstensional and the phases B and C in the lateralmovement regime). The equivalence of the phasesimplicates tectonic unity in both quarries. The tectonicunity in combination with mentioned difference in thefault plane orientations among quarries (compareFigs. 4 and 5) may indicate the fault movementscorresponding to the tectonic phases A ,B and Cproceeded along given (already existing) planes. Twocrossing kinematic indicators found on several fault

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5. CONCLUSIONS Limestone body is intersected by four sets of

fractures (subvertical W-E fractures, subvertical NW-SE, subvertical N-S fractures and subhorizontalfractures). The tectonic regime in the limestone bodyvaried during its history. Two parts of the bodyrepresented by the quarries I and II assigned ratherdistinct character of fracturing and faulting because ofsome rotation. Four different tectonic phases schemewere proposed. Three concordant phases wereidentified in both quarries (two lateral movements anda transtensional regime). This indicates integraltectonic evolution of the limestone body since therotation. The fourth phase is possibly linked to theoverthrusting and compressive regime mappedpreviously. The results of presented work correspondwith and confirm earlier works.

ACKNOWLEDGEMENTS

The research was supported by the Ministry ofEducation, Youth and Sport research program(LC506), by the Grant Agency of the CharlesUniversity (43-258020) and by Institute of RockStructure and Mechanics AS CR, v.v.i. (AVOZ30460519). I am very grateful to J. Jelínek andunknown reviewer for their helpful and constructivereviews. I would like to thank my friends andcolleagues, particularly Z. Fučík, F. Hrouda, V.Schenk, Z. Schenková for indispensable technicalsupport, J. Málek, P. Štěpančíková and J. Žák for valuable feedback, discussions and advances, J.Mašek for covering the quarries with panoramicphotos, Prof. F. Salvini for free use of software Daisy3_470.6, J. Žalohar for free use of software T-TectoProfessional 2 and my husband P. Novák for hispatience.

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