56 research outputs found
Geoenvironmental Characterization of Sulfide Mine Tailings
Spain has a long mining tradition dating from pre-historic times up to the present day. The cessation of mining activity has generated a large amount of mine wastes, most of which represent geochemical hazards. Mine tailings are watery sludge composed of medium-to-fine-grained material, resulting from grinding and mineral processing (e.g., galena, pyrite, sphalerite, and arsenopyrite). They entail both an accumulation and a potential subsequent emission source of trace elements (i.e. As, Cu, Fe, Pb, and Zn) with formation of acid mine drainage (AMD). Mineralogical and geochemical techniques (in combination with geophysical surveys and aerial photographs studies) have been jointly applied to selected mine areas. Seven mine deposits from the most important mine districts in Spain have been selected: Iberian Pyrite Belt, Cartagena-La Unión, Alcudia Valley, and Mazarrón. The main goal is focused on getting a geoenvironmental characterization as complete as possible by determining the geometry, evolution in time and composition of mine ponds, and the possible occurrence of AMD, for identifying related environmental hazards
A Geochemical and Geophysical Characterization of Sulfide Mine Ponds at the Iberian Pyrite Belt (Spain)
This work presents the results of a geochemical
and geophysical characterization of the
Monte Romero and La Naya mine ponds, belonging
to the Cueva de la Mora and Riotinto mine districts,
respectively, based on mineralogical, geochemical and
geophysical techniques. In order to obtain a representative
environmental characterization, two deposits
showing different mineralogies, physico-chemical
parameters, chemical compositions of tailings and
pond conditions were selected. Monte Romero mine
tailings showed an upper level mainly composed of
silicates and a deeper level mainly composed of
sulfides and barite. The toxic metal content was
different in both levels but high enough to exceed
the regional legal concentration limits for agricultural
soils. An electrical resistivity tomography survey
revealed a homogeneous upper unit (3 m thickness),
which displayed low resistivity values, corresponding
to water-saturated silt and clay materials with an
abundance of sulfides which was interpreted as the
pond infilling. The La Naya mine pond presented a
homogeneous mineralogical composition made up of
quartz as the main mineral and chlorite-smectite and
jarosite as accessory phases. The absence of sulfide
phases and the low contents of metal elements are
directly related to the reworking processes of the
sludge dumped in this pond. The geophysical survey
revealed that the pond infilling did not have a
constant thickness, but ranged between 15 and
20 m. An inner groundwater flow in the infilling
was recognized. The low resistivity values allowed
the presence of acid waters and related subsurface
flows to be identified in both mine ponds, but no acid
water drainage occurred across their vessels. When
compared to the Aznalcóllar tailings spill, the La
Naya pond is large enough to release a similar amount
of sludge, but of a very low metal content. The Monte
Romero sludge displays a similar, potentially toxic
metal content to the Aznalcóllar sludge, but its size is
significantly smaller
A Geochemical and Geophysical Characterization of Sulfide Mine Ponds at the Iberian Pyrite Belt (Spain)
(The original publication is available at www.springerlink.com)This work presents the results of a geochemical
and geophysical characterization of the
Monte Romero and La Naya mine ponds, belonging
to the Cueva de la Mora and Riotinto mine districts,
respectively, based on mineralogical, geochemical and
geophysical techniques. In order to obtain a representative
environmental characterization, two deposits
showing different mineralogies, physico-chemical
parameters, chemical compositions of tailings and
pond conditions were selected. Monte Romero mine
tailings showed an upper level mainly composed of
silicates and a deeper level mainly composed of
sulfides and barite. The toxic metal content was
different in both levels but high enough to exceed
the regional legal concentration limits for agricultural
soils. An electrical resistivity tomography survey
revealed a homogeneous upper unit (3 m thickness),
which displayed low resistivity values, corresponding
to water-saturated silt and clay materials with an
abundance of sulfides which was interpreted as the
pond infilling. The La Naya mine pond presented a
homogeneous mineralogical composition made up of
quartz as the main mineral and chlorite-smectite and
jarosite as accessory phases. The absence of sulfide
phases and the low contents of metal elements are
directly related to the reworking processes of the
sludge dumped in this pond. The geophysical survey
revealed that the pond infilling did not have a
constant thickness, but ranged between 15 and
20 m. An inner groundwater flow in the infilling
was recognized. The low resistivity values allowed
the presence of acid waters and related subsurface
flows to be identified in both mine ponds, but no acid
water drainage occurred across their vessels. When
compared to the Aznalcóllar tailings spill, the La
Naya pond is large enough to release a similar amount
of sludge, but of a very low metal content. The Monte
Romero sludge displays a similar, potentially toxic
metal content to the Aznalcóllar sludge, but its size is
significantly smaller.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu
Microdeformation of lacustrine laminite sequences from Late Miocene formations of SE Spain: an interpretation of loop bedding.
Lacustrine laminated sediments (laminites) present in Late Miocene formations of the Híjar Basin, SE Spain, display well developed loop bedding, a structure consisting of bundles of laminae that are sharply constricted at intervals, giving a morphology of loops or links of a chain. The laminite sequences, which are interbedded with turbidite marlstones, were accumulated on the bottom of a permanently stratified lake developed in a rapidly subsiding basin limited by 010° and 105° normal faults. As deduced from both macro‐ and microdeformational analyses, the basin evolved under an extensional stress field throughout the Late Miocene. Four main types of loops, simple and complex loops with subcategories, have been recognized within the laminite sequence. Simple loops of type 1 show the best definite pattern, quite similar to ‘pinch and swell structures’, a type of boudinage typical of stretching of alternating beds where the competence contrast is not strongly marked. The remaining loop types display contortion and occasional breakage of laminae (microfaulted edges) indicative of microdeformation near the boundary between the ductile‐brittle deformational fields. The distribution of the various loop types across the laminite sequence reflects an interplay between progressive lithification of the laminites as sedimentation progressed and tectonic stresses which affected the sediment sequence. Accordingly, a mechanism of deformation under an extensional stress field, ultimately related to the creep movement of the main basin faults which resulted in successive seismic shocks of low magnitude, is proposed to explain the formation of loop bedding in the laminites
Characterization of volcanic materials using shallow geophysical techniques: 1. Electrical resistivity imaging
Volcanic deposits and structures are characterized by a high variability in both geometry and physical
properties. These changes are common not only in a vertical direction but in the horizontal one too. As a
result, the geophysical study of this kind of materials has to be performed using a technique that combines
a good horizontal and vertical resolution. Electrical resistivity imaging has been applied to the study of
three profiles in different places of Tenerife island. The examples shown in this work are the location of
lava tubes, the determination of the depth to the boundary of different lava flows, and the geometry at
depth of a basaltic dyke intruding in pyroclastic deposits. In all the cases, the technique has revealed as a
useful tool to determine the geometry and depth of different volcanic materials and therefore, the geophysical
characterization of volcanic area
Características de los tensores de esfuerzos activos entre la Dorsal Centroatlántica y la Península Ibérica.
The orientation of the principal stresses and the principal stress difference ratio has been determined along the southwestern boundary of the Euroasiatic plate with Northamerican and African plates by inversion method of focal mechanisms of earthquakes. The ridge push (30~ to 65Q N) ranges from E-W to ESE-WSW, with R values that show a triaxial extensional stress. The state of stress changes to strike-slip regime in the transform fault zones, and the Shmax strike turns clockwise to NW in the dextral strike-slip faults and counterclockwise to the NE in the sinistral ones. Along the margin between the Euroasiatic-African plates, from the Azores triple junction to Algeria, Shmax keeps a constant NW-SE strike but the stress ratio values range from triaxial extensional stress state, to the West, to uniaxial compresive stress state, to the East, passing through a strike-slip regime in the middle zone. In this context and with a widely NWSE Shmax, strike-slip and extensional stresses prevail in most Iberian peninsula, whereas southwards it is dominated by uniaxial compresive stresses
Study and Evolution of the Dune Field of La Banya Spit in Ebro Delta (Spain) Using LiDAR Data and GPR
La Banya spit, located at the south of the River Ebro Delta, is a sandy formation, developed by annexation of bars forming successive beach ridges, which are oriented and modeled by the eastern and southern waves. The initial ridges run parallel to the coastline, and above them small dunes developed, the crests of which are oriented by dominant winds, forming foredune ridges and barchans. This study attempted to test a number of techniques in order to understand the dune dynamic on this coastal spit between 2004 and 2012: LiDAR data were used to reconstruct changes to the surface and volume of the barchan dunes and foredunes; ground-penetrating radar was applied to obtain an image of their internal structure, which would help to understand their recent evolution. GPS data taken on the field, together with application of GIS techniques, made possible the combination of results and their comparison. The results showed a different trend between the barchan dunes and the foredunes. While the barchan dunes increased in area and volume between 2004 and 2012, the foredunes lost thickness. This was also reflected in the radargrams: the barchan dunes showed reflectors related to the growth of the foresets while those associated with foredunes presented truncations associated with storm events. However, the global balance of dune occupation for the period 2004-2012 was positive
An active tectonic field for CO2 storage management: the Hontomín onshore case study (Spain)
One of the concerns of underground CO2 onshore
storage is the triggering of induced seismicity and fault reactivation by the pore pressure increasing. Hence, a comprehensive analysis of the tectonic parameters involved in the
storage rock formation is mandatory for safety management
operations. Unquestionably, active faults and seal faults depicting the storage bulk are relevant parameters to be considered. However, there is a lack of analysis of the active
tectonic strain field affecting these faults during the CO2
storage monitoring. The advantage of reconstructing the tectonic field is the possibility to determine the strain trajectories and describing the fault patterns affecting the reservoir
rock. In this work, we adapt a methodology of systematic
geostructural analysis to underground CO2 storage, based on
the calculation of the strain field from kinematics indicators
on the fault planes (ey and ex for the maximum and minimum horizontal shortening, respectively). This methodology
is based on a statistical analysis of individual strain tensor
solutions obtained from fresh outcrops from the Triassic to
the Miocene. Consequently, we have collected 447 fault data
in 32 field stations located within a 20 km radius. The understanding of the fault sets’ role for underground fluid circulation can also be established, helping further analysis of
CO2 leakage and seepage. We have applied this methodology
to Hontomín onshore CO2 storage facilities (central Spain).
The geology of the area and the number of high-quality outcrops made this site a good candidate for studying the strain
field from kinematics fault analysis. The results indicate a
strike-slip tectonic regime with maximum horizontal shortening with a 160 and 50◦ E trend for the local regime, which
activates NE–SW strike-slip faults. A regional extensional
tectonic field was also recognized with a N–S trend, which
activates N–S extensional faults, and NNE–SSW and NNW–
SSE strike-slip faults, measured in the Cretaceous limestone
on top of the Hontomín facilities. Monitoring these faults
within the reservoir is suggested in addition to the possibility of obtaining a focal mechanism solutions for microearthquakes (M < 3)This work has been partially supported by the European Project ENOS: ENabling Onshore CO2 Storage in Europe, H2020 Project ID: 653718 and the Spanish project 3GEO, CGL2017-83931-C3-2-P, MICIU-FEDE
- …