In the Late Permian, the Hercynian orogeny
uplifted the northwestern basin and formed a series of high-angle thrust faults (Figure 1(b)).
The main structural features of the study area are the consequences of the Hercynian orogeny
. Tectonically, the study area is part of a region of horsts and grabens that is characterized by brittle tectonics (Figure 4).
Its origin is very old (Paleozoic) and correspond to rocks formed during the Hercynian orogeny
, which were later covered by sediments and resurfaced over them during the subsequent Alpine Orogeny (Diaz Martinez et al.
It is believed that the onset of generation was delayed until well after the Hercynian orogeny
. Traps are found in faulted anticlines.
An Alpine stress field must have been established which was probably very similar to that maintained in the Hercynian orogeny
. As a result, Variscan shear zones likely were locally reactivated at higher crustal levels.
Additionally, there was a sudden decrease in their distribution number in Triassic, which is in accordance with the Hercynian orogeny
at the end of Devonian.
Regional-scale doming, probably related to the Hercynian Orogeny
, produced a network of fractures throughout the Alston Block, and these served as pathways for mineralizing solutions driven by heat emanating from the underlying Weardale granite pluton.
It is suggested that this remagnetization was caused by low-temperature hydrothermal circulation due to the influence of the Caledonian or Hercynian orogeny
Folding during the Hercynian orogeny
and subsequent erosion has left an exposed cap of gossan with a 20-30 m thick layer of rich secondary sulphide overlying an irregular pyritic and chalco-pyritic stockwork.
The first episode occurred in relation to the Middle Caledonian Orogeny during the Late Ordovician, the second one in association with the Early Hercynian Orogeny
during the Late Devonian, and the third one in response to the Late Hercynian Orogeny
during the Late Permian [23, 24].
The geodynamic tensions of the Hercynian orogeny
which had reunited all the continental blocks in the Pangea stopped and this immense continent started to crack and break up.