N Etemad-Saeed; M. H Adabi; A. Sadeghi; M. Hosseini- Barzi
Abstract
This work is focused on tectonic provenance of the Late Neoproterozoic Kahar Formation in the northern Iran. KaharMountain (type locality) provides valuable information on tectonic events during this time. The Kahar Formation in this area is a well preserved sedimentary sequence and consists of about ...
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This work is focused on tectonic provenance of the Late Neoproterozoic Kahar Formation in the northern Iran. KaharMountain (type locality) provides valuable information on tectonic events during this time. The Kahar Formation in this area is a well preserved sedimentary sequence and consists of about 1000 meters of predominantly fine grained siliciclastic rocks and minor sandstones, conglomerates and dolomitized stromatolites. Kahar lithic arkose sandstones with low compositional and textural maturity, contain abundant feldspar (plagioclase and K feldspar), quartz, and volcanic lithic fragments and have an average composition of Q38F40L22, Qt39F40L21, Qm32F40Lt28,Qp27Lvm60Lsm13 and Qm44P33K23 suggesting a proximal source and a dissected arc setting. The type of lithic fragments in the sandstones show andesitic and felsic volcanic rock sources. Heavy mineral analysis (abundant metastable and unstable minerals such as biotite, and pyroxenes) indicate that Kahar sandstones were derived from unroofing of arc-type magmatic rocks. The low diversity of heavy mineral assemblages in the Kahar sandstones indicates that the source rocks were uniform and localized. Considering the two common tectonic views regarding the Late Neoproterozoic condition of Iran (rift-passive margin and magmatic arc-subduction zone), the results of this study which confirm the magmatic arc tectonic setting of Alborz-Iran at that time seems critical.
M. Hosseini-Barzi; M. Saeedi
Abstract
The sandstones of Padeha Formation with 390m thickness in section of Samirkooh in Kerman, Zarand have been studied to illuminate their provenance, tectonic provenance, diagenesis by omitting the effect of diagenetic process on sandstone composition. In this direction, petrography of 91 thin sections, ...
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The sandstones of Padeha Formation with 390m thickness in section of Samirkooh in Kerman, Zarand have been studied to illuminate their provenance, tectonic provenance, diagenesis by omitting the effect of diagenetic process on sandstone composition. In this direction, petrography of 91 thin sections, modal analysis of 30 appropriate samples, and use of SEM and EDX analyses of 6 sandstone samples were accomplished .We can point to diagenetic processes including mechanical compaction, coating hematite around the detrial grains (eogenetic stage) and growing up authigenic cholorite and illite, chemical compaction, quartz cementation, dolomite cementation, dedolomitization, albitization of feldspar and corrosion of grains by dolomite cement (mesogenetic stage) and fracturing as well as filling them by calcite, quartz and anhydrite cement (telogenetic stage). We studied tectonic provenance of these sandstones using Qt92 F7 L1, Qm77 F 7 Lt 16, Qp92Lvm4Lsm4, after recognition of diagenetic process and omitting their effect on the results of modal analysis. These results show quartzolithic facies with cratonic, recycled orogen and rifted continental margin tectonic provenance. Using diamond diagram drawn based on particulars quartz grains and also petrographic evidences in these sandstone, we can say that these sandstone derived from multi provenance. The log Qt/F+RF vs. Qt/F+RF climate diagram and QRRF triangle indicate humid climate during deposition of the Padeha Formation.