Geology Reference
In-Depth Information
intervals). The water mixing model indicates that the waters from the
crestal areas of local structures in the Oligocene-Lower Miocene complex
(Asmari Fm.) include up to 20% of the foreign Jurassic component, and
in the Upper Cretaceous (Bangostan Series), up to 50%. If we assume that
the cross-flow occurs in the entire stratigraphic range from Cambrian to
Lower Miocene, then the fraction of the injected ingredient in the Jurassic
complex (300 g/l) is about 10%, in the Upper Cretaceous 8% and in the
Oligocene-Lower Miocene 5%.
The available data are insufficient for a substantial judgment about the
origin of the sediment cover brines in the region. Tentatively it may be
suggested that the major factors in their formation were dissolution of the
section's evaporites superposed over the normal metamorphism of the
depositional waters in the water complexes' sedimentation basins.
The composite Table of major hydrochemical parameters including
geology, salinity and ion composition of Alpine mobile belt regions' ground
water complexes (Table 2.21) enables their comparison.
Based on the study of all reviewed data about the analyzed Alpine mobile
belt regions the following general conclusions were drawn:
1. In all basins the present-day spatial hydrogeochemical
zoning in the sediment cover of III and IV order tectonic
elements is formed under the dominating influence of large-
scale vertical ground water cross-flows from the lower to the
upper stratigraphic intervals within the depth range from 10
km to the surface.
2. A typical feature of all regions without exception is the
presence in the upper hydrogeological stage of contrast-
ing hydrogeochemical anomalies disturbing regional back-
ground; they are caused by the vertical (down to up) ground
water cross-flows.
3. The major ground water transit paths in the vertical section
are: regional faults; faults on the local structures; contact
zones of diapir intrusions; areas of elevated fracturing in car-
bonate reservoirs; eruption apparatuses of mud volcanoes;
hydrogeological «windows», etc., playing the role of hydro-
dynamic drain.
4. Regional zones and local areas of oil- and gas-accumulation
are spatially conjugated and functionally associated with
hydrochemical anomalies of the cross-flow origin.
5. The vertical hydrogeochemical zoning in most Alpine
regions within the drilled intervals is normal.
