Open Session - SWISS GEOSCIENCE MEETINGs

2.36
Geochemistry and Source of the Recent Sediments in Southwestern of
Ahvaz, Khouzestan Province, Iran
Zarasvandi. A
Department of Geology, Shahid Chamran University, Ahvaz, Iran zarasvandi_a@scu.ac.ir
The Ahvaz City is located in Khouzestan province in southwest of Iran. This city is the most important geographical and industrial
city between Iran and Iraq border. The climate of the study area is considered to be arid and humid. This area is part
of Zagros orogenic belt and consists of Cenozoic sedimentary rocks such as Limestone (Asmari Formation), Gypsum
(Gachsaran Formation), Sandstone (Aghajari Formation) and Conglomerate (Bakhtiari Formation). This belt is the product of
three major geotectonic events during subduction between the Arabian and Iranian plates. The belt consists of there parallel
tectonic zones from NE to SW: (1) the volcanic–plutonic zone (Urumieh– Dokhar belt); (2) the Sanandaj-Sirjan metamorphic
zone; (3) the Zagros fold belt.
The rock fragments and minerals in the study area derived from erosion of the banks of the rivers and sand dunes in the
southwest of the area. The surficial distribution of sediments shows miscellaneous layers and mixture of sands, silts and
hard muds. The study area is characterized by the predominance of alluvial and sedimentary rocks of both chemical and
detrital origins. Except for some unpublished exploration reports there are no other published literature about the geology,
geochemistry, economic geology and genesis of these sediments. The combination of petrography and geochemistry data of
the sediments can reveal the nature and tectonic setting of sediments as main indicators for mineral exploration in the
surficial sediments. In this way, 30 samples from alluvial deposits and sand dunes were collected for geochemical and petrography
using XRF and XRD methods.
Petrographical studies and using major element discrimination diagrams indicate that these sediments are classified as litharenite,
sublitharenite, and subarkose types. Petrographic studies using XRD reveal that these sediments are mainly consist
of quartz, feldspars, Muscovite, Biotite, clay minerals, heavy minerals and fragments of Igneous and metamorphic rocks.
Tectonic setting discrimination diagrams based on major elements show that most of samples fall in an active continental
margin. Geochemical characteristics suggest that in addition to quartzose recycled sedimentary rocks plutonic igneous or
high-grade metamorphic rocks can be as parent rocks for these sediments. Based on all data can conclude these sediments
are result of erosion of sandstone and conglomerate rocks in the study area which are formed by erosion of felsic plutonic
and metamorphic rocks of the Sanandaj-Sirjan metamorphic belt. These sedimentary rocks were deposited along the passive
marginal coast of the Oligocene-Miocene Zagros foreland basin.
REFERENCES
Alavi, M., 2004, Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution: American Journal
of Science, 304, 1–20.
Nesbitt, H.W., Young, G.M., 1982, Early Proterozoic climates and plate motions inferred from major element chemistry of
lutites: Nature, 299, 715–717.
Pettijohn, F.J., Potter, P.E., Siever, R., 1972, Sand and Sandstones: New York, Springer-Verlag.
Roser, B.P., Korsch, R.J., 1986, Determination of tectonic setting of sandstone –mudstone suites using SiO 2 content and K 2 O/
Na 2 O ratio:Journal of Geology, 94, 635–650.
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Symposium 2: Mineralogy-Petrology-Geochemistry