Determination of stress directions using section and surfacecriteria in fibrous gypsum veins samples North Muqdadia(Al-Sidoor)/ East Iraq

Ali TAHA, Munther

	Determination of stress directions using section and surfacecriteria in fibrous gypsum veins samples North Muqdadia(Al-Sidoor)/ East Iraq
Diyala Journal For Pure Science
Article 1, Volume 7, Issue 2, 2011, Pages 39-62
Author
Munther Ali TAHA
Abstract
Many fibrous gypsum veins have been studied in Al-Sidoor area North Muqdadia city, EastIraq; the study used surface and section criteria for estimating the stress phases directions thatthe study area have been undergone. These veins grow in Injana Formation (Upper Miocene)which is conspicuous in the axial region of Southern Hemrin anticline; cropping out withinhorizontal beds of Sandstone, Marl and Siltstone. The study area effected by many tectonicevents after the deposition of Injana and Muqdadia Formations in Late Miocene (8 Millionsyear. These tectonic events have recognized from the study of gypsum fibrous veins. Threetypes of veins measurement have achieved; the first one attains a general study on veinsattitude; the second one studies plunge and azimuth of the fibers in the vein after themeasuring of the attitude of the veins in the bed; and the third type studies of slip movementon vein surfaces. The first type gave one extension direction perpendicular to the veins planes,this extension plunges toward the Southwest. The second type indicates that the study areapassed firstly by an extensive stage. The minimum stress axis (¥ٍ3) is plunged by an angleabout 30¨¬ toward the Southwest. This stage followed by another extensive stage related tonormal fault system, its minimum stress axis (¥ٍ3) is oriented Northwest-Southeast. After thatthe maximum principal stress axis ( ¥ٍ1) has been rotated from the vertical to the horizontal,then it suffered clock wise rotation from the direction Northwest-Southeast to North-South,then to Northeast-Southwest and finally to East-West. Win Tensor Method of Delvaux hasexamined the third type of measurement, on the paleostress reconstruction. Three stages haverecognized; the older one is extensive stage. The plunge and azimuth of (¥ٍ1) are at 65/098;(¥ٍ2) at 24/295; and (¥ٍ3) at 06/202, the value of R is 0.67. The intermediate stage iscompressive and ¥ٍ1 at 12/001, ¥ٍ2 at 05/092 and ¥ٍ3 at 77/204, the value of R is 0.43, and theounger stage is compressive and ¥ٍ1 at 04/078, ¥ٍ2 at 40/345 and ¥ٍ3 at 50/173, the value of Ris 0.45.

Statistics Article View: 64 PDF Download: 10