Elsevier

Tectonophysics

Volumes 728–729, 20 March 2018, Pages 41-54
Tectonophysics

Hematite (U-Th)/He thermochronometry constrains intraplate strike-slip faulting on the Kuh-e-Faghan Fault, central Iran

https://doi.org/10.1016/j.tecto.2018.01.023Get rights and content

Highlights

  • Hematite (U-Th)/He thermochronometry refines Kuh-e-Faghan fault evolution.

  • Fault nucleation, fluid circulation and hematite mineralization at from 12 to 7 Ma

  • Ongoing fault propagation and exhumation from 7 Ma to present

  • Tectonic reorganization of central Iran may have initiated <7 Ma.

Abstract

The Kuh-e-Faghan strike-slip fault system (KFF), located to the northern edge of the Lut Block in central Iran, developed through a Neogene-Quaternary pulsed history of eastward fault propagation and fault-related exhumation. This system is a consequence of the residual stresses transmitted from the Arabia-Eurasia convergent plate boundary. Here we integrate structural and textural analysis with new and previously published apatite fission-track (AFT) and apatite (U-Th)/He (apatite He) results, chlorite thermomentry, and hematite (U-Th)/He data from hematite-coated brittle fault surfaces to constrain the timing of tectonic activity and refine patterns of late Miocene-Pliocene burial and exhumation associated with the propagation of the KFF. Twenty-nine hematite (U-Th)/He (hematite He) dates from three striated hematite coated slip surfaces from the KFF fault core and damage zone yield individual dates from ~12–2 Ma. Petrographic analysis and chlorite thermometry of a polyphase, fossil fluid system in the KFF fault core document that fluid circulation and mineralization transitioned from a closed system characterized by pressure solution and calcite growth to an open system characterized by hot hydrothermal (T = 239 ± 10 °C) fluids and hematite formation. Hematite microtextures and grain size analysis reveal primary and secondary syntectonic hematite fabrics, no evidence of hematite comminution and similar hematite He closure temperatures (~60–85 °C) in each sample. Integration of these results with thermal history modeling of AFT and apatite He data shows that KFF activity in the late Miocene is characterized by an early stage of fault nucleation, fluid circulation, hematite mineralization, and eastward propagation not associated with vertical movement that lasted from ~12 to 7 Ma. Hematite He, AFT, and apatite He data track a second phase of fault system activity involving fault-related exhumation initiating at ~7 Ma and continuing until present time. Our new data constrain the onset of the recognized Late Miocene-Pliocene tectonic reorganization in north-central Iran.

Introduction

Strike-slip faulting is the primary process by which horizontal crustal movements are accommodated and stresses are transferred away from a continental collision front into the intraplate domain (Allen et al., 2003; Molnar and Tapponnier, 1975; Nilforoushan et al., 2003; Vernant et al., 2004; Walpersdorf et al., 2014). The development and evolution of intraplate strike-slip fault systems can be punctuated in time and space and, commonly, linked to stress-state changes at the collisional plate boundaries (Calzolari et al., 2016a; Ellis, 1996; Glorie and De Grave, 2016; Spotila et al., 2007; van Hinsbergen et al., 2015; Webb and Johnson, 2006). Constraining the timing, rate, and kinematics of intraplate strike-slip faulting is fundamental to (i) assess the spatio-temporal distribution and modes of accommodation of far-field stresses away from plate boundaries; (ii) gain first-order insight into the dynamic response and stress propagation pathway from plate margins to intraplate domains; and (iii) reconstruct regional-scale tectonic events that may have been partially or totally obliterated along the plate margin domains by intense deformation.

Documenting the timing of brittle faulting in strike slip systems is critical for addressing these issues. This is classically achieved through relative dating approaches such as comparing the stratigraphic age of the faulted units and or by constraining strike-slip fault-related exhumation through bedrock low-temperature thermochronology (e.g., Ehlers and Farley, 2003). Limited geochronological methods exist for direct dating of fault activity. These include 40Ar/39Ar dating of authigenic illite in fault gouge (e.g., Duvall et al., 2011; van der Pluijm et al., 2001) and pseudotachylyte glasses (Di Vincenzo et al., 2012; Magloughlin et al., 2001; Sherlock et al., 2004), zircon fission-track dating of pseudotachylytes (Seward and Sibson, 1985; Tagami and O'Sullivan, 2005), and U-Pb (Nuriel et al., 2017, Nuriel et al., 2012) and U-Th-Pb dating of syntectonic calcite (Serpelloni et al., 2013; Williams et al., 2017). Hematite (U-Th)/He (hematite He) dating of hematite-coated fault surfaces (e.g., Ault et al., 2015; McDermott et al., 2017; Moser et al., 2017) provides an attractive target to resolve the timing and mechanisms of deformation in the brittle upper crust owing to the ubiquity of hematite in these settings, He retention over geologic time scales, and connections between hematite texture and hematite He dates that reflect different deformation processes. For example, hematite He thermochronometry may provide timing constraints on synkinematic hematite mineralization (e.g., Moser et al., 2017) or a record of the post hematite formation thermal history of the evolving fault system.

Owing to its extensive exposure and comparatively young geologic history, the Kuh-e-Faghan fault (KFF) is an ideal fault system to apply hematite He thermochronometry to document the timing and deformation processes associated with intraplate strike-slip faulting. The KFF is a major dextral fault at the northern boundary of the Lut block in central Iran (Fig. 1). The long-term tectonic evolution of the KFF has been interpreted as the intra-plate response to the evolution of the Arabia-Eurasia collision since the Early Miocene (Calzolari et al., 2016a). Prior work implies a punctuated deformation history and the eastward propagation of the KFF (Calzolari et al., 2016a; Calzolari et al., 2016b); however, the timing of this history is poorly resolved.

In this study, we present new hematite He thermochronometry data from a suite of striated, hematite-coated fault surfaces in the fault core and damage zone of the KFF to constrain episodes of fault slip on this major intraplate strike-slip fault system in central Iran. To accurately interpret the hematite He dates, we assess the structurally-controlled paleo-fluid conditions of hematite mineralization; the morphology, grain-size distribution, and textural fabrics of the hematite crystals; and the time-temperature (t-T) history of the host rock from conventional low-temperature thermochronometry. This approach allows us to identify different fault-related processes by discriminating between hematite mineralization and fault system related exhumation. These data refine the timing of faulting linked to Late Miocene-early Pliocene exhumation and regional tectonic reorganization of central Iran. Our results show that hematite He thermochronometry is an effective tool in investigating the spatio-temporal evolution of intracontinental strike-slip fault systems.

Section snippets

Tectonic setting of the Kuh-e-Faghan fault system

The Arabia-Eurasia collision zone is located along the Mesozoic-Cenozoic Alpine-Himalayan convergence zone (Fig. 1). Arabia-Eurasia convergence initiated in the mid-Jurassic (Agard et al., 2011, Agard et al., 2005) and culminated with the closure of the Neotethys ocean and polyphase continental collision (Agard et al., 2005; Bagheri and Stampfli, 2008; Jolivet and Faccenna, 2000; McCall, 1997; Mouthereau et al., 2012; Rossetti et al., 2010, Rossetti et al., 2014; Şengör, 1990; Stampfli and

Materials and methods

This study focuses on the eastern fault strand (EFS) of the KFF, where diffuse hematite mineralization, including hematite-coated fault surfaces, are preserved and the youngest (<5 Ma) fault-related exhumation occurred (Calzolari et al., 2016a). To characterize the structurally controlled paleofluid circulation and hematite mineralization conditions during faulting, we combined field structural analysis of the EFS structure and associated slip surfaces with description of the hematite-bearing

Fault zone architecture, structural analysis, and hematite occurrence

The EFS is a ~40-km-long, sub-vertical fault system comprising several synthetic faults that coalesce to form a curvilinear slip zone and prominent range front. The strike of this system changes from NW-SE to E-W at its eastward termination (Fig. 1). Faults form a decameter-to-hectometer-thick damage zone that consists of numerous mesoscale fault strands, which cut across the pre-Neogene basement units that are now tectonically juxtaposed against the Neogene successions (Fig. 3A and B;

Discussion

The multidisciplinary approach applied in this study refines the spatio-temporal burial, exhumation, and faulting history associated with the propagation of the KFF in intraplate, central Iran. New AFT results provide insight into basin deposition and thermal history. AFT dates from Neogene samples IR13 and IR18 are older than their stratigraphic age, indicating that ambient basin temperatures were insufficient (<100 °C) to fully reset the AFT system during the Neogene evolution of the KFF

Conclusions

We integrate structural and textural analysis with hematite He dating of brittle faults, AFT and apatite He thermochronometry, and thermal history modeling to constrain the timing and style of fault activity along a stike-slip fault system that cannot be readily dated with traditional geochronologic tools. Our new AFT thermochronometry data reveal that detrital apatite grains contained within the basal Neogene units where sourced from the Paleozoic-Mesozoic basement adjacent to Kuh-e-Faghan

Acknowledgements

Special thanks to M.R. Mazinani for assistance during fieldwork. The manager and staff of Khanyeh-e-Moallem of Kashmar are warmly thanked for their kind hospitality. We also thank Ali Rastpour and Hassan Faraji for driving to the field and logistic support. T. Theye is thanked for his advice during chlorite thermometry analysis. We gratefully acknowledge P. Reiners, U. Chowdhury, and E. Abel of the Arizona Radiogenic Helium Dating Laboratory for analytical assistance with the hematite He

References (104)

  • H.J. Lippolt et al.

    Paragenetic specularite and adularia (Elba, Italy): concordant (U+Th)-He and K-Ar ages

    Earth Planet. Sci. Lett.

    (1995)
  • S. Madanipour et al.

    Synchronous deformation on orogenic plateau margins: insights from the Arabia–Eurasia collision

    Tectonophysics

    (2013)
  • M. Mattei et al.

    Oroclinal bending in the Alborz Mountains (Northern Iran): new constraints on the age of South Caspian subduction and extrusion tectonics

    Gondwana Res.

    (2017)
  • G.J.H. McCall

    The geotectonic history of the Makran and adjacent areas of southern Iran

    J. Asian Earth Sci.

    (1997)
  • R.G. McDermott et al.

    Thermochronometric and textural evidence for seismicity via asperity flash heating on exhumed hematite fault mirrors, Wasatch fault zone, UT, USA

    Earth Planet. Sci. Lett.

    (2017)
  • A.C. Moser et al.

    (U–Th)/He thermochronometry reveals Pleistocene punctuated deformation and synkinematic hematite mineralization in the Mecca Hills, southernmost San Andreas Fault zone

    Earth Planet. Sci. Lett.

    (2017)
  • F. Mouthereau et al.

    Building the Zagros collisional orogen: timing, strain distribution and the dynamics of Arabia/Eurasia plate convergence

    Tectonophysics

    (2012)
  • A.M.M. Robert et al.

    Structural evolution of the Kopeh Dagh fold-and-thrust belt (NE Iran) and interactions with the South Caspian Sea Basin and Amu Darya Basin

    Mar. Pet. Geol.

    (2014)
  • A.H. Robertson et al.

    The Berit transect of the Tauride thrust belt, S Turkey: Late Cretaceous–Early Cenozoic accretionary/collisional processes related to closure of the Southern Neotethys

    J. Asian Earth Sci.

    (2006)
  • E. Shabanian et al.

    Plio-Quaternary stress states in NE Iran: Kopeh Dagh and Allah Dagh-Binalud mountain ranges

    Tectonophysics

    (2010)
  • G.M. Stampfli et al.

    A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons

    Earth Planet. Sci. Lett.

    (2002)
  • P. Agard et al.

    Convergence history across Zagros (Iran): constraints from collisional and earlier deformation

    Int. J. Earth Sci.

    (2005)
  • P. Agard et al.

    Zagros orogeny: a subduction-dominated process

    Geol. Mag.

    (2011)
  • J.L. Allen et al.

    Structural geometry and thermal history of pseudotachylyte from the Homestake shear zone, Sawatch Range, Colorado

    Field Guides

    (2002)
  • M. Allen et al.

    Late Cenozoic reorganization of the Arabia-Eurasia collision and the comparison of short-term and long-term deformation rates

    Tectonics

    (2004)
  • M.B. Allen et al.

    Contrasting styles of convergence in the Arabia-Eurasia collision: why escape tectonics does not occur in Iran

    Geol. Soc. Am. Spec. Pap.

    (2006)
  • M.B. Allen et al.

    Right-lateral shear across Iran and kinematic change in the Arabia-Eurasia collision zone

    Geophys. J. Int.

    (2011)
  • A. Amini

    Provenance and Depositional Environment of the Upper Red Formation, Central Zone Iran

    (1997)
  • A. Amini

    Red colouring of the Upper Red Formation in central part of its basin, central zone, Iran

    J. Sci. Islam. Repub. Iran

    (2001)
  • A.K. Ault et al.

    Linking hematite (U-Th)/He dating with the microtextural record of seismicity in the Wasatch fault damage zone, Utah, USA

    Geology

    (2015)
  • A.K. Ault et al.

    Record of paleofluid circulation in faults revealed by hematite (U-Th)/He and apatite fission-track dating: an example from Gower Peninsula fault fissures, Wales

    Lithosphere

    (2016)
  • J. Austermann et al.

    The role of the Zagros orogeny in slowing down Arabia-Eurasia convergence since ~5 Ma

    Tectonics

    (2013)
  • G.J. Axen et al.

    Exhumation of the west-central Alborz Mountains, Iran, Caspian subsidence, and collision-related tectonics

    Geology

    (2001)
  • R. Bahr et al.

    Temperature-induced 4He degassing of specularite and botryoidal hematite: a 4He retentivity study

    J. Geophys. Res.

    (1994)
  • P. Ballato et al.

    Tectonic control on sedimentary facies pattern and sediment accumulation rates in the Miocene foreland basin of the southern Alborz mountains, northern Iran

    Tectonics

    (2008)
  • P. Ballato et al.

    Arabia-Eurasia continental collision: insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran

    Geol. Soc. Am. Bull.

    (2011)
  • P. Ballato et al.

    Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains, north Iran

    Tectonics

    (2013)
  • J.T. Buscher et al.

    Near-field response to transpression along the southern San Andreas fault, based on exhumation of the northern San Gabriel Mountains, southern California

    Tectonics

    (2007)
  • J.S. Caine et al.

    Fault zone architecture and permeability structure

    Geology

    (1996)
  • G. Calzolari et al.

    Spatio-temporal evolution of intraplate strike-slip faulting: the Neogene–Quaternary Kuh-e-Faghan Fault, central Iran

    Geol. Soc. Am. Bull.

    (2016)
  • G. Calzolari et al.

    Geomorphic signal of active faulting at the northern edge of Lut block: insights on the kinematic scenario of Central Iran

    Tectonics

    (2016)
  • F. Cifelli et al.

    The architecture of brittle postorogenic extension: results from an integrated structural and paleomagnetic study in north Calabria (southern Italy)

    Geol. Soc. Am. Bull.

    (2007)
  • F. Cifelli et al.

    Tectonic magnetic lineation and oroclinal bending of the Alborz range: implications on the Iran-Southern Caspian geodynamics

    Tectonics

    (2015)
  • W. Devlin et al.

    South Caspian basin: young, cool, and full of promise

    GSA today

    (1999)
  • G. Di Vincenzo et al.

    Constraining the timing of fault reactivation: Eocene coseismic slip along a Late Ordovician ductile shear zone (northern Victoria Land, Antarctica)

    Geol. Soc. Am. Bull.

    (2012)
  • S. Ellis

    Forces driving continental collision: reconciling indentation and mantle subduction tectonics

    Geology

    (1996)
  • N.S. Evenson et al.

    Hematite and Mn oxide (U-Th)/He dates from the Buckskin-Rawhide detachment system, western Arizona: gaining insights into hematite (U-Th)/He systematics

    Am. J. Sci.

    (2014)
  • K.A. Farley et al.

    Radiometric dating and temperature history of banded iron formation–associated hematite, Gogebic iron range, Michigan, USA

    Geology

    (2015)
  • P.G. Fitzgerald et al.

    Uplift and denudation of the central Alaska ange - a case-study in the use of apatite fission-track thermochronology to determine absolute uplift parameters

    J. Geophys. Res. Solid Earth

    (1995)
  • K. Gallagher

    Transdimensional inverse thermal history modeling for quantitative thermochronology

    Journal of Geophysical Research: Solid Earth

    (2012)
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