International Journal of Geosciences, 2010, 1, 66-69
doi:10.4236/ijg.2010.12009 Published Online August 2010 (http://www.SciRP.org/journal/ijg)
Determining the Relative Age of Fault Activity through
Analyses of Gouge Mineralogy and Geochemistry: A Case
Study from Vápenná (Rychleby Mts), Czech Republic
Lucie Nováková, Pavel Hájek, Martin Šťastný
Institute of Rock Structure and Mechanics, Academy of Sciences, v.v.i., Prague, Czech Republic
Received June 1, 2010; revised June 29, 2010; accepted July 16, 2010
Abstract
The relative age of fractures can be determined through structural analyses in the field or through the detailed
mineralogical (XRD) and chemical analyses (AAS method, volumetric, and gravimetric analysis) of fault
gouge in the laboratory. The aim of this work was to compare these approaches. It was hypothesised that the
two methods would yield consistent results. The studied faults were located in the Rychleby Mts, part of the
Sudetic Marginal Fault Zone. The relative age of the faults was determined in the field through the applica-
tion of the intersection law. The fault gouges were sampled in a crystalline limestone quarry near the village
of Vápenná. The mineralogical composition of the fault gouges has been established by XRD analysis of
powder samples and analysis of preferentially oriented clay minerals. From our result, it is clear that these
two approaches yielded consistent results with regard to the relative age of the faults.
Keywords: Crystalline Limestone, Intersecting Faults, Fault Gouge, Relative Chronology
1. Introduction
The study of brittle tectonics incorporates a wide range
of discontinuities from the micro-scale (e.g. cracks and
joints) to the mega-scale (e.g. fault zones). Elucidating
the relative age of intersecting fractures is a fundamental
part of structural geology. However, the technique is
rarely described in depth. Hancock [1] demonstrated that
it is possible to determine the relative age of fault and
joint sets. Groshong [2] described the intersection of
faults as sequential or contemporaneous. Sequential
faulting defines an older fault that is cut and displaced by
a younger fault. Jeong and Cheong [3] provided direct
evidence for multiple fault movements through an inves-
tigation of the mineralogy, micromorphology, and chem-
istry of fault gouge.
Fault gouge is a fine-grained breccia formed by the
crushing of rocks and minerals. This crushing is induced
by fracturing and frictional sliding during fault move-
ments [4]. The constituents of gouge are assumed to be
derived from materials in the hanging wall and footwall
blocks. The mineralogy and chemistry, however, sug-
gests a quite different origin [3]. From chemical and
X-ray analysis, it is seen that clay gouge has a polymin-
eral composition. The main constituents of gouge are
quartz, illite, and kaolinite. In addition, also recognised
are small amounts of chlorite, smectite, mixed layer il-
lite-smectite, and gypsum [5-8].
The aim of this study is to undertake field investiga-
tions and laboratory analyses in order to test these two
underlying methods. It is hypothesised that the chemical
and X-ray analyses will yield results that are consistent
with the classical structural interpretation.
2. Geological Situation
The Rychleby Mts are situated in the northeastern part of
the Bohemian Massif (Czech Republic) along its border
with Poland (Figure 1). The area is characterised by
several significant geological boundaries, such as the
Ramzová and Nýznerov overthrusts. These overthrusts
are usually assumed to mark the contact between the
Lugicum and Silezicum domains [9]. To the east, the
area is bordered by the important Sudetic Marginal Fault
Zone (SMFZ). This zone, which extends for 250 km, has
been investigated in detail by many authors [10-14]. It
originates in Poland before passing into the Czech Re-
public. Here, the fault lies close to the towns of Javorník
and Jeseník. It terminates on the marginal Jeseník Fault
near the town of Opava [15]. Near the village of Váp-

L. NOVÁKOVÁ ET AL.
67
enná, the Sudetic Marginal Fault separates the crystalline
limestones of the Branná group from the Žulová granite
pluton.
The crystalline limestones close to Vápenná are of
Devonian age. In the bedrock are quartzites and phyllites
[16,17]. The predominant mineral is usually calcite but
locally may be graphite. In addition, also identified are
flogopite, muscovite, chlorite, grains of pyrite, and py-
rolusite with goethite. Within the crystalline limestones
there are smaller veins of an ochre calcite coloured by
iron oxides and hydroxides [18]. About 15 km to the
south, hydrothermal copper mineralization has been de-
scribed in detail at Horní Lipová [19]. About 10 km to
the northeast, an occurrence of contact minerals was de-
scribed in the Žulová granite pluton at Vycpálek Quarry.
These minerals were formed at the contact of the crystal-
line limestones and the Žulová granite pluton [20]. The
association of minerals between adjacent rock formations
represents a probable source for the mineral composition
within the fault gouges. There is a simple quartzite min-
eralisation comprising quartz and, predominately, seric-
ite-muscovite but also with sporadic biotite. Another
association is comprised of phyllites with smaller layers
of green schists and metamorphosed fine-grained diabase
tuffs [17].
3. Methodology
Two fault planes were chosen as the basis for this meth-
odological case study. These faults represent the main
fracture orientations in the area, namely the Sudetic
(NW-SE) and the Moravo-Silesian (NE-SW) (Nováková,
2008). Figure 2 shows that Fault A, orientated in the
Moravo-Silesian direction, is offset by about 22 cm
along Fault B, in the Sudetic direction. Fault A strikes
Figure 1. A simplified geological map of the study area in
the northeastern part of the Bohemian Massif, Czech Re-
public (modified after Nováková, 2009).
296° and dips 66°, whereas Fault B strikes 65° and dips
31°.
The XRD method is based on the interaction between
the sample and X-radiation. It is a very accurate method
and produces high quality results for all types of samples.
The mineralogical composition of the fault gouges was
determined through the diffraction analysis of samples
with randomly orientated particles in addition to the
analysis of samples with preferentially orientated parti-
cles. The samples were suspended in solution and al-
lowed to settle on the glass slide. A Philips PW 7310
X-ray difractograph was set to CuKα emission, voltage
40 kV, current 40 mA, scanning speed 1° min-1 spreading
between 3 to 70° 2 for randomly orientated samples
(Figure 3) and 3 to 35° 2 for preferentially orientated
samples (Figure 4). The obtained X-ray data were inter-
preted in accordance with Micheev [21] and Swarthmore
[22]. The chemical analyses of the samples were under-
taken using the AAS method, volumetric, and gravimet-
ric analysis.
4. Results
The relative age of the faults was determined during field
investigations. Fault A is cut and displaced along Fault B
and therefore, according to the intersection law [2], Fault
A is older than Fault B. The gouge from Fault A contains
crushed carbonates and carbonated breccias of up to 2
cm surrounded by clay-sand matrix. When the larger
debris was inspected it was possible to find tiny amounts
of muscovite and chlorite, or crystals of calcite with iron
oxides, hydroxides, and quartz. In addition, feldspars and
plagioclases are occasionally present. The gouge from
Fault B contains carbonate debris and breccias with in-
sipid crystals and a higher proportion of clay matrix. The
debris is smaller than about 1 cm. Table 1 and 2 present
Figure 2. The studied faults: the older fault (Fault A) is
intersected and displaced along the younger fault (Fault B).
The offset is about 22 cm.

L. NOVÁKOVÁ ET AL.
68
Figure 3. An example (sample A) of the X-ray diffraction
curve for randomly orientated samples (for an angle 2, it
is possible to measure between 0° and 90°).
Figure 4. An example (sample A) of the X-ray diffraction
curve for preferentially orientated samples (for an angle 2,
it is possible to measure between 0° and 40°).
the results of X-ray diffraction and chemical analysis
respectively.
The colour of both fault gouges is grey to ochre. The
gouge from Fault B contains a huge mass of clay miner-
als with grains smaller than 0.004 mm. Most of the clay
is either smectite (up to 60%) or illite (up to 22%). The
proximal surrounding basic rocks are the obvious source
of the minerals. In addition, the clay matrix also contains
small amount of kaolinite, quartz, K-feldspar, amphibole,
and chrome-chlorite (Table 2). Chemically, the gouge
consists primarily of SiO2, TiO2 and iron. The results of
the both analyses point to a significant input into the
gouge from more distal rocks such as quartzites, phyllites,
and green schists.
The gouge from Fault A is more ochre than that ob-
served in Fault B. The clay matrix is formed predomi-
nately of illite, kaolinite, and quartz. Smectite and feld-
spars are present but less important. In addition, there are
minor amounts of calcite, amphibole, and goethite. The
chemistry is dominated by CaO. The crushed limestones
and calcites in the sample demonstrate the importance of
the proximal surrounding crystalline limestones. How-
ever, the sample may also be partly derived from more
distal rocks. As more stable minerals are found in sample
A, it is possible to suggest that the gouge in Fault A is
older than the gouge in Fault B. This proposal is in
agreement with the previous observations of Skácel [11].
5. Discussion and Conclusions
The intersecting faults, A and B on Figure 2, were lo-
cated in a quarry close to the village of Vápenná. These
faults follow regionally important orientations. Field
observations allowed a relative fault chronology to be
proposed. Fault A is cut and displaced along Fault B and
therefore, according to the intersection law, Fault A is
older than Fault B. From this, it is possible to suggest
that the last movement along the Sudetic fault plane oc-
curred after the last movement along the Moravo-Sile-
sian fault plane. The fault gouges were studied from both
a mineralogical and chemical perspective.
These characteristics of the gouges corroborate the
field observations. Fault A contains crushed calcite and
this fault was later sealed by recrystallised calcite. Reac-
tivation of this calcite vein led to the formation of the
calcite powder seen at the base of the gouge in Fault A.
This fault has subsequently been cut by Fault B. The
strong influence of more distal (i.e., non-limestone)
rocks in the gouge is predominately represented by SiO2.
Despite the small number of studied faults, both the
field investigation and laboratory analyses yield consis-
Table 1. The results of the X-ray diffraction of the fault
gouges (qualitative analysis and semi-quantitative estimate
of content of minerals).
Minerals [%]
Samples SChIK Q Kf Plg AmGeCa
A-random sample12 -61 22 2 - 32 52
A-oriented sample764310 20 7 - 223
B-random sample 12-10 2 41 7 1 --27
B-oriented sample604227 4 1 - 2--
Table 2. The results of the chemical analysis of the fault
gouges.
Sample A [%] Sample B [%]
SiO2 23,86 59,99
TiO2 0,46 0,84
Al2O3 9,49 9,46
Fe2O3 4,43 4,72
FeO 0,14 0,55
MnO 0,091 0,134
MgO 1,33 1,68
CaO 29,78 7,79
Na2O 0,05 0,08
K2O 1,27 2,1
P2O5 0,12 0,18
- H2O 1,88 1,80
Ignition loss 28,66 12,14
Cr 66 [mg.kg-1] 94 [mg.kg-1]

L. NOVÁKOVÁ ET AL.
69
tent results regarding the relative age of the faults. These
indicate that Fault A is older than Fault B. It is consid-
ered that this combined approach promises to provide
new opportunities in the study of relative fault chronolo-
gies. Moreover, this study suggests that robust results
may be obtained through X-ray and chemical analyses in
places where it has hitherto not been possible to deter-
mine the relative age of the faults through detailed struc-
tural investigations.
6. Acknowledgements
The research was funded by the Grant Agency of Charles
University (43-258020), the Institute of Rock Structure
and Mechanics AS CR, v.v.i. (A VOZ30460519), the
Ministry of Education, Youth and Sports (LC506) and
the Czech Science Foundation (250/09/1244). We are
grateful to the reviewer for the constructive review and
to our colleagues and friends for useful discussions, ad-
vances and technical support. M. D. Rowberry provided
a critical revision of the English.
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