TY - JOUR
T1 - Two new microscopic ductile kinematic indicators from the Oman Mountains
AU - Scharf, Andreas
AU - Mattern, Frank
AU - Pracejus, Bernhard
N1 - Funding Information:
The manuscript greatly benefitted from the critical comments of the reviewers Christopher von Hagke (RWTH Aachen, Germany) and two anonymous reviewers as well as the Editor Joao Hippertt (Universidad Nacional de Salta, Argentina). In addition we want to particularly thank Cees Passchier (Universität Mainz) for his support by explaining the drag mechanism of rotating objects in ductile shear zones. For the preparation of thin sections we thank Hamdan Al-Zidi and Bader Al-Waili (both Sultan Qaboos University, Oman). Structural data were plotted and back rotation were calculated with the open software ‘Stereonet 10’ of R.W. Allmendinger. For the micro-analytical measurements (EDS and SEM) we wish to thank Mr. Ibrahim Al Khusaibi, CAARU/SQU.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2019/2
Y1 - 2019/2
N2 - Two novel shear-sense indicators were observed in different tectonic settings. The first one (“PDT”) occurs in a calcmylonite, associated with extension. The second one (“Dragged Intergrowths”) was discovered in mylonitized plagiogranite (trondhjemite) dikes with vertical to sub-vertical foliation and strike-slip deformation within harzburgite. The calcite mylonite displays shear planes, characterized by parallel laminae which differ in composition. They contain light-colored, calcite, while darker impurities consist of hematite, goethite, and rutile. PDTs are associated with microthrusts. The thrusts form an acute angle with the mylonitic foliation. Thrusting between two microthrusts created pull-aparts, filled with drusy calcite. The shear sense of the PDTs is revealed by (1) shortening and related imbrication of the thrust laminae, (2) pull-apart structures and (3) drag folds at either end of the microthrusts. The indicated shear is confirmed by independent evidences. One PDT is up to ∼0.5 mm wide and 1 mm long. The mylonitized plagiogranite contains a K-feldspar δ-porphyroclast (2 mm long), featuring dragged K-feldspar/quartz intergrowth due to rotation during high-temperature conditions. Bending occurs on either end of the object. The original orientation of the intergrowth was subparallel to the foliation. As a result an “S”-shaped object formed. The deduced shear sense is independently confirmed.
AB - Two novel shear-sense indicators were observed in different tectonic settings. The first one (“PDT”) occurs in a calcmylonite, associated with extension. The second one (“Dragged Intergrowths”) was discovered in mylonitized plagiogranite (trondhjemite) dikes with vertical to sub-vertical foliation and strike-slip deformation within harzburgite. The calcite mylonite displays shear planes, characterized by parallel laminae which differ in composition. They contain light-colored, calcite, while darker impurities consist of hematite, goethite, and rutile. PDTs are associated with microthrusts. The thrusts form an acute angle with the mylonitic foliation. Thrusting between two microthrusts created pull-aparts, filled with drusy calcite. The shear sense of the PDTs is revealed by (1) shortening and related imbrication of the thrust laminae, (2) pull-apart structures and (3) drag folds at either end of the microthrusts. The indicated shear is confirmed by independent evidences. One PDT is up to ∼0.5 mm wide and 1 mm long. The mylonitized plagiogranite contains a K-feldspar δ-porphyroclast (2 mm long), featuring dragged K-feldspar/quartz intergrowth due to rotation during high-temperature conditions. Bending occurs on either end of the object. The original orientation of the intergrowth was subparallel to the foliation. As a result an “S”-shaped object formed. The deduced shear sense is independently confirmed.
KW - Dragged intergrowth features in K-feldspar porphyroclast
KW - PDT (pull-apart, drag folds, microthrusts)
KW - Shear-sense indicator in calcmylonite and granite
KW - δ object
UR - http://www.scopus.com/inward/record.url?scp=85059326837&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85059326837&partnerID=8YFLogxK
U2 - 10.1016/j.jsg.2018.12.006
DO - 10.1016/j.jsg.2018.12.006
M3 - Article
AN - SCOPUS:85059326837
SN - 0191-8141
VL - 119
SP - 107
EP - 117
JO - Journal of Structural Geology
JF - Journal of Structural Geology
ER -