Two new microscopic ductile kinematic indicators from the Oman Mountains

Andreas Scharf, Frank Mattern, Bernhard Pracejus

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)107-117
Number of pages11
JournalJournal of Structural Geology
Volume119
DOIs
Publication statusPublished - Feb 1 2019

Fingerprint

kinematics
foliation
mountain
plagiogranite
calcite
feldspar
thrust
imbrication
trondhjemite
mylonite
harzburgite
rutile
goethite
tectonic setting
hematite
drag
dike
indicator
quartz
fold

Keywords

  • Dragged intergrowth features in K-feldspar porphyroclast
  • PDT (pull-apart, drag folds, microthrusts)
  • Shear-sense indicator in calcmylonite and granite
  • δ object

ASJC Scopus subject areas

  • Geology

Cite this

Two new microscopic ductile kinematic indicators from the Oman Mountains. / Scharf, Andreas; Mattern, Frank; Pracejus, Bernhard.

In: Journal of Structural Geology, Vol. 119, 01.02.2019, p. 107-117.

Research output: Contribution to journalArticle

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