Summary:
This project research concerns the study of the transgressive series of
limestone overlying Fe-Ni-lateritic deposits in the Municipality of
Aspropyrgos, Attica, Greece, as well as the lateritic sedimentary ore itself.
These laterites are formed by weathering of (ή) the altered ophiolitic parent
rocks and fill the karstic cavities of the upperjurassic limestones, dolomitic
limestones and dolomites of the Eastrern Greece platform (subpelagonian zone)
which are found in a section called “Kaki Rachi” area. To elucidate the age of
the transgression, the microfauna of the transgressive series was studied and
were attributed an age of Upper Cenomanian.
The definition of the age of the transgressive series was based on the presence
of characteristic benthic trematophores found in thin intersections of samples
derived from cores of five test drillings made in this area from TITAN CEMENT
COMPANY. Study of the phases proved a neritic environment of sedimentation in a
shallow intern platform.
The mineralogical composition of the studied laterites was investigated with
optical microscopy and X-ray diffraction (XRD; Bruker D5000 power
diffractometer) also with the use of TOPAS software, whole rock analysis with
X-Ray Fluorescence and phase mineral analysis with electron microprobe (SEM &
SEM-EDS).
Representative samples from the Fe-Ni ore zone, mainly through the five
vertical profiles from the cores of the drillings and additionally by the
sampling of in-situ rocks, were analyzed for their chemical composition using
XRF. All the selected ore samples were analyzed for REE.
The “Kaki-Rachi” Fe-Ni-laterite ore is mainly composed of hematite, goethite,
quartz, magnetite, chlorite, kaolinite and chromite which grains with
cataclastic texture are found as residual components inherited from the
ophiolithic parent rocks. The ore is both of massive and pissolitic type. The
pissolites are hematitic contained in a fine-grained groundmass, comprising
clastic grains of quartz and chromite or Cr-spinel as well as chert fragments
embedded in a matrix that consists mainly of hematite, quartz, goethite,
chlorite, magnetite, serpentinite and kaolinite.
The Fe-Ni deposit is characterized by high content of SiO2, with an average
value of 55 wt% and 30% wt% for the Fe-minerals (Hematite, goethite, magnetite
and maghemite which, apart from hematite, are found mostly in the matrix).
Chlorite is the main Ni-bearing mineral of the laterite while the Fe-minerals
exhibit considerable concentrations. The NiO content for the specimens examined
as far as chlorite is concerned ranges between 3.16 and 8.63 wt%. Respectively
the Fe-minerals have a NiO content ranging between 0.59 – 1.88 wt%. In the
deposit of “Kaki Rachi” the average Ni concentration is 0.71 wt% ranging
between 0.28 and 1.45 wt%.
In order to calculate the volume of the deposit, a buffer zone of the drill
holes was identified and criteria have been defined to categorize the
μετάλλευμα ore, using primarily accordingly to the content of Ni at first and
secondly that of Fe. For the 3d transformation of the geological
characteristics of the formations related with metaloforia the mineralization
and the identification estimation of Ni-Fe ores resource in the study area, we
used the following software: cad Microstation Descartes V8.2.1, Autocad Map
ver. 13.25.1, GIS ArcInfo Esri13.51 and ArcGIS 10.1. The DTM analysis was made
by photogrammetric procedure using photogrammetric station (software and
specific hardware).
3D views were produced for an area of 100.000m2 calculating the volumes of
indicated mineral resource which were found to be 1.425.060 m3. Of them
66.887m3 concern high in Ni (Ni0,9 wt.%) content ore reserve and the rest
1.358.173 m3 concern ore reserves with the content of Ni ranging between 0,5 –
0,9 wt.%.
The REE concentrations are generally low in the samples examined, from less
than 50ppb to a few hundred parts per billion.
Keywords:
Aspropyrgos, Laterite, Palaeoenvironment, Reserves