Structural patterns and their role in the formation of alteration and mineralization in the Western Yemen rift-related volcanics

Abstract EN

The structural patterns in the rift-related volcanic area are greatly associated with the major tectonic components of the Red Sea and less commonly with the Gulf of Aden.

The Cenozoic volcanic faults have a WNW (290-300°) trend.

In the south westernmost region these faults are considered as feeders for volcanic activity.

Most volcanic dikes follow the same trend of faulting (WNW) while some other faults striking N-NW (330-350°) characterize those structures that are more or less parallel to the main Red Sea trend.

The majority of these structures are normal faults trending NE in the volcanic area and follow the transform system in the Red Sea trough.

Also, the east-west and north-south faults play an important role in controlling mineralization.

The central (Dhamar) and southern (Ad Dhala) regions are formed in the Tertiary (probably Early Miocene) and consistent with the graben formation, which became troughs for a relatively younger volcanic activity.

Calderas are also significant as they are considered to be the source structures of huge pyroclastics found at the upper part of the volcanic pile.

The magnetic map reveals large magnetic domains trending northwest, west-northwest, and east-west influencing over the distribution of hydrothermal systems.

The hydrothermally altered areas are relatively large, widely distributed and probably related to preexisting basement structures.

Tertiary intrusions have risen preferentially to high crustal levels throughout the basement structures while groundwater penetrated a great depth along fractures and fault systems producing alteration haloes.

This suggests that Tertiary intrusions are shallow and continuous to deep structural levels, if compared with other extensional areas.

The shallow intrusions tend to develop hydrothermal circulation cells with the best potential for generating gold deposits in Yemen.