Литосфера (Jan 2016)
A new geological and geophysical interpretation to potential felds near ESRU. The paper 1. Wesern part of the Urals
Abstract
A new 2D-model of geological structure in the vicinity of Europrobe seismic reflection profiling in the Urals (ESRU) was built to the depth of 15 km. For the first time as a result of analysis of anomalous fields behavior on the parallel profiles in 2D-modeling of density and magnetic properties of the region the applicability of the method was estimated. It was modeled deep seating magnetic body situated under the gravity active layer. Probably this body discontinuing here and there is a continuation of the body revealed in the west part of the Urals Reflection Seismic profile (Urseis). Versions of interpretation of the body were discussed: 1. Block of Precambrian metamorphous rocks with ferruginous quartzite; 2. Block of ocean type rock or mantle diapir (plum). The former is more possible. At the West the upper (up to 3.15-4.8 км depth) part of the section is represented by early Permian terrigenous sediments. Below in the model is a formation (thickness from 0.7 km at the West, up to 1.7 km at the East) of light clastic rocks, below of which situated more dens limestones of middle Paleozoic with thickness from 0.7 km to 1.5 km at the East. The deepest layer of sediment section is constructed from mainly terrigenous thickness of 1.1-1.3 km. The bottom part of the model represents structures of Russian platform basement that moving further to the East submerge under the Ural structures. At 107-125 km along profile the basement intrusion of gabbro-diorite has emerged. From 126 to 142 km along profile one can see a block of terrigenous rocks that probably is a graben of Russian platform. A comparison has been made for blocks of the basement and known ancient metamorphous complexes of the west slope of the Urals (Taratash, etc.). From 169 km along profile one can note falling to the East and broadening with depth highly magnetized body, which probably is serpentinized ultramafic rocks. To this part of the profile Sarany ultramafic intrusion is projected. Ultrabasite zircon age is 1756 ± 12 Ma. Two superimposed stages of zircon formation 464 ± 5 and 439 ± 3 Ma is possibly to be interpreted as age of tectonic ultramafite re-processing. Thus Sarany intrusion probably is the uppest part of the big block situated in 30 km to the West and structurally below Main Ural Deep Fault
