skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Cenozoic kinematic histories of the Tidding and Lohit thrusts in the northern Indo-Burma Ranges: Implications for crustal thickening and exhumation of Gangdese lower arc crust along the Indus-Yarlung suture zone
Title: Cenozoic kinematic histories of the Tidding and Lohit thrusts in the northern Indo-Burma Ranges: Implications for crustal thickening and exhumation of Gangdese lower arc crust along the Indus-Yarlung suture zone
Crustal thickening has been a key process of collision-induced Cenozoic deformation along the Indus-Yarlung suture zone, yet the timing, geometric relationships, and along-strike continuities of major thrusts, such as the Great Counter thrust and Gangdese thrust, remain inadequately understood. In this study, we present findings of geologic mapping and thermo- and geochronologic, geochemical, microstructural, and geothermobarometric analyses from the easternmost Indus-Yarlung suture zone exposed in the northern Indo-Burma Ranges. Specifically, we investigate the Lohit and Tidding thrust shear zones and their respective hanging wall rocks of the Lohit Plutonic Complex and Tidding and Mayodia mélange complexes. Field observations are consistent with ductile deformation concentrated along the top-to-the-south Tidding thrust shear zone, which is in contrast to the top-to-the-north Great Counter thrust at the same structural position to the west. Upper amphibolite-facies metamorphism of mélange rocks at ∼9−10 kbar (∼34−39 km) occurred prior to ca. 36−30 Ma exhumation during slip along the Tidding thrust shear zone. To the north, the ∼5-km-wide Lohit thrust shear zone has a subvertical geometry and north-side-up kinematics. Cretaceous arc granitoids of the Lohit Plutonic Complex were emplaced at ∼32−40 km depth in crust estimated to be ∼38−52 km thick at that time. These rocks cooled from ca. 25 Ma to 10 Ma due to slip along the Lohit thrust shear zone. We demonstrate that the Lohit thrust shear zone, Gangdese thrust, and Yarlung-Tsangpo Canyon thrust have comparable hanging wall and footwall rocks, structural geometries, kinematics, and timing. Based on these similarities, we interpret that these thrusts formed segments of a laterally continuous thrust system, which served as the preeminent crustal thickening structure along the Neotethys-southern Lhasa terrane margin and exhumed Gangdese lower arc crust in Oligocene−Miocene time.  more » « less
Award ID(s):
1914501 2210074 2210075 1914503
PAR ID:
10381386
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
GSA Bulletin
ISSN:
0016-7606
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Geosciences)
    Carosi, Rodolfo; da Costa Campos Neto, Mario; Fossen, Hakkon; Montomoli, Chiara; Simonetti, Matteo; Martinez-Frias, Jesus (Ed.)
    North-trending rifts throughout south-central Tibet provide an opportunity to study the dynamics of synconvergent extension in contractional orogenic belts. In this study, we present new data from the Dajiamang Tso rift, including quantitative crustal thickness estimates calculated from trace/rare earth element zircon data, U-Pb geochronology, and zircon-He thermochronology. These data constrain the timing and rates of exhumation in the Dajiamang Tso rift and provide a basis for evaluating dynamic models of synconvergent extension. Our results also provide a semi-continuous record of Mid-Cretaceous to Miocene evolution of the Himalayan-Tibetan orogenic belt along the India-Asia suture zone. We report igneous zircon U-Pb ages of ~103 Ma and 70–42 Ma for samples collected from the Xigaze forearc basin and Gangdese Batholith/Linzizong Formation, respectively. Zircon-He cooling ages of forearc rocks in the hanging wall of the Great Counter thrust are ~28 Ma, while Gangdese arc samples in the footwalls of the Dajiamang Tso rift are 16–8 Ma. These data reveal the approximate timing of the switch from contraction to extension along the India-Asia suture zone (minimum 16 Ma). Crustal-thickness trends from zircon geochemistry reveal possible crustal thinning (to ~40 km) immediately prior to India-Eurasia collision onset (58 Ma). Following initial collision, crustal thickness increases to 50 km by 40 Ma with continued thickening until the early Miocene supported by regional data from the Tibetan Magmatism Database. Current crustal thickness estimates based on geophysical observations show no evidence for crustal thinning following the onset of E–W extension (~16 Ma), suggesting that modern crustal thickness is likely facilitated by an underthrusting Indian lithosphere balanced by upper plate extension. 
    more » « less
  2. ; ; ; ; ; ; ; (, Geosphere)
    null (Ed.)
    Abstract Recovering the time-evolving relationship between arc magmatism and deformation, and the influence of anisotropies (inherited foliations, crustal-scale features, and thermal gradients), is critical for interpreting the location, timing, and geometry of transpressional structures in continental arcs. We investigated these themes of magma-deformation interactions and preexisting anisotropies within a middle- and lower-crustal section of Cretaceous arc crust coinciding with a Paleozoic boundary in central Fiordland, New Zealand. We present new structural mapping and results of Zr-in-titanite thermometry and U-Pb zircon and titanite geochronology from an Early Cretaceous batholith and its host rock. The data reveal how the expression of transpression in the middle and lower crust of a continental magmatic arc evolved during emplacement and crystallization of the ∼2300 km2 lower-crustal Western Fiordland Orthogneiss (WFO) batholith. Two structures within Fiordland’s architecture of transpressional shear zones are identified. The gently dipping Misty shear zone records syn-magmatic oblique-sinistral thrust motion between ca. 123 and ca. 118 Ma, along the lower-crustal WFO Misty Pluton margin. The subhorizontal South Adams Burn thrust records mid-crustal arc-normal shortening between ca. 114 and ca. 111 Ma. Both structures are localized within and reactivate a recently described >10 km-wide Paleozoic crustal boundary, and show that deformation migrated upwards between ca. 118 and ca. 114 Ma. WFO emplacement and crystallization (mainly 118–115 Ma) coincided with elevated (>750 °C) middle- and lower-crustal Zr-in-titanite temperatures and the onset of mid-crustal cooling at 5.9 ± 2.0 °C Ma−1 between ca. 118 and ca. 95 Ma. We suggest that reduced strength contrasts across lower-crustal pluton margins during crystallization caused deformation to migrate upwards into thermally weakened rocks of the mid-crust. The migration was accompanied by partitioning of deformation into domains of arc-normal shortening in Paleozoic metasedimentary rocks and domains that combined shortening and strike-slip deformation in crustal-scale subvertical, transpressional shear zones previously documented in Fiordland. U-Pb titanite dates indicate Carboniferous–Cretaceous (re)crystallization, consistent with reactivation of the inherited boundary. Our results show that spatio-temporal patterns of transpression are influenced by magma emplacement and crystallization and by the thermal structure of a reactivated boundary. 
    more » « less
  3. ; ; ; ; (, GSA Bulletin)
    null (Ed.)
    Abstract Terrane accretion forms lithospheric-scale fault systems that commonly experience long and complex slip histories. Unraveling the evolution of these suture zone fault systems yields valuable information regarding the relative importance of various upper crustal structures and their linkage through the lithosphere. We present new bedrock geologic mapping and geochronology data documenting the geologic evolution of reactivated shortening structures and adjacent metamorphic rocks in the Alaska Range suture zone at the inboard margin of the Wrangellia composite terrane in the eastern Alaska Range, Alaska, USA. Detrital zircon uranium-lead (U-Pb) age spectra from metamorphic rocks in our study area reveal two distinct metasedimentary belts. The Maclaren schist occupies the inboard (northern) belt, which was derived from terranes along the western margin of North America during the mid- to Late Cretaceous. In contrast, the Clearwater metasediments occupy the outboard (southern) belt, which was derived from arcs built on the Wrangellia composite terrane during the Late Jurassic to Early Cretaceous. A newly discovered locality of Alaska-type zoned ultramafic bodies within the Clearwater metasediments provides an additional link to the Wrangellia composite terrane. The Maclaren and Clearwater metasedimentary belts are presently juxtaposed by the newly identified Valdez Creek fault, which is an upper crustal reactivation of the Valdez Creek shear zone, the Late Cretaceous plate boundary that initially brought them together. 40Ar/39Ar mica ages reveal independent post-collisional thermal histories of hanging wall and footwall rocks until reactivation localized on the Valdez Creek fault after ca. 32 Ma. Slip on the Valdez Creek fault expanded into a thrust system that progressed southward to the Broxson Gulch fault at the southern margin of the suture zone and eventually into the Wrangellia terrane. Detrital zircon U-Pb age spectra and clast assemblages from fault-bounded Cenozoic gravel deposits indicate that the thrust system was active during the Oligocene and into the Pliocene, likely as a far-field result of ongoing flat-slab subduction and accretion of the Yakutat microplate. The Valdez Creek fault was the primary reactivated structure in the suture zone, likely due to its linkage with the reactivated boundary zone between the Wrangellia composite terrane and North America in the lithospheric mantle. 
    more » « less
  4. ; ; ; ; ; ; (, Terra Nova)
    Abstract Recent advancements in quantitatively estimating the thickness of Earth's crust in the geologic past provide an opportunity to test hypotheses explaining the tectonic evolution of southern Tibet. Outstanding debate on southern Tibet's Cenozoic geological evolution is complicated by poorly understood Mesozoic tectonics. We present new U‐Pb geochronology and trace element chemistry of detrital zircon from modern rivers draining the Gangdese Mountains in southern Tibet. Results are similar to recently published quantitative estimates of crustal thickness derived from intermediate‐composition whole rock records and show ~30 km of crustal thinning from 90 to 70 Ma followed by thickening to near‐modern values from 70 to 40 Ma. These results extend evidence of Late Cretaceous north–south extension along strike to the west by ~200 km, and support a tectonic model in which an east–west striking back‐arc basin formed along Eurasia's southern margin during slab rollback, prior to terminal collision of India with Eurasia. 
    more » « less
  5. (, Geological Society of America abstracts)
    We explore the growth of lower-continental crust by examining the root of the Southern California Batholith, a ~ 500-km-long, paleo-arc segment of the Mesozoic California arc that lies between the southern Sierra Nevada batholith and northern Peninsular Ranges Batholith. We focus on the Cucamonga and San Antonio terranes located in the eastern San Gabriel Mountains where the deep root of the Mesozoic arc is exhumed by the Quaternary Cucamonga thrust fault. This lower- to mid-crustal cross section of the arc allows us to investigate: 1) the timing and rates of Mesozoic arc construction, 2) mechanisms of sediment incorporation into the lower crust, and 3) the interplay between mantle input and crustal recycling during arc magmatic surges. We use detrital zircon geochronology of 4 quartzites and paragneisses to investigate the origin of the lower-crustal Cucamonga paragneiss sequence, and U-Pb petrochronology of 26 orthogneisses to establish the timing of arc magmatism and granulite-facies metamorphism. We find that the Cucamonga paragneisses share broad similarities to Sur Series metasedimentary rocks in the Salinia terrane, suggesting that both were deposited in a Late Paleozoic to Early Mesozoic forearc or intra-arc basin. This basin was progressively underthrust beneath the arc during the Middle Jurassic to Late Cretaceous and was metamorphosed during two high-grade (>750°C) migmatization events at ca. 124 and 89–75 Ma. These metamorphic events were associated with 100 m.y. of arc magmatism that lasted from 175 to 75 Ma and culminated in a magmatic surge from ca. 90–75 Ma. Field observations and petrochronology analyses indicate that partial melting of the underthrust Cucamonga metasedimentary rocks was triggered by emplacement of voluminous, mid-crustal tonalites and granodiorites. Partial melting of the metasedimentary rocks played a subsidiary role relative to mantle input in driving the Late Cretaceous magmatic flare-up event. Our observations demonstrate that tectonic incorporation of sediments into the lower crust led to structural, compositional and rheological changes in the architecture of the arc including vertical thickening. These structural changes created weak zones that preferentially focused deformation and promoted present-day reactivation along the Cucamonga thrust fault. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email