Titanite Fission Track Research Articles

Thermo-tectonic history of the Issyk-Kul basement (Kyrgyz Northern Tien Shan, Central Asia)

Lake Issyk-Kul occupies a large Late Mesozoic–Cenozoic intramontane basin between the mountain ranges of the Northern Kyrgyz Tien Shan. These ranges are often composed of granitoid basement that forms part of a complex mosaic assemblage of microcontinents and volcanic arcs. Several granites from the Terskey, Kungey, Trans-Ili and Zhetyzhol Ranges were dated with the zircon U/Pb method (SHRIMP, LA-ICP-MS) and yield concordant Late Ordovician–Silurian (~456–420Ma) emplacement ages. These constrain the “Caledonian” accretion history of the Northern Kyrgyz Tien Shan in the amalgamated Palaeo-Kazakhstan continent. The ancestral Tien Shan orogen assembled in the Early Permian when final closure of the Turkestan Ocean ensued collision of Palaeo-Kazakhstan and Tarim. A Late Palaeozoic structural basement fabric formed and Middle–Late Permian post-collisional magmatism added to crustal growth of the Tien Shan. Permo‐Triassic cooling (~300–220Ma) of the ancestral Tien Shan was unraveled using 40Ar/39Ar K-feldspar and titanite fission-track (FT) thermochronology on the Issyk-Kul granitoids. Apatite thermochronology (FT and U–Th–Sm/He) applied to the broader Issyk-Kul region elucidates the Meso-Cenozoic thermo-tectonic evolution and constrains several tectonic reactivation episodes in the Jurassic, Cretaceous and Cenozoic. Exhumation of the studied units occurred during a protracted period of intracontinental orogenesis, linked to far-field effects of Late Jurassic–Cretaceous accretion of peri-Gondwanan blocks from the Tethyan realm to Eurasian. Following a subsequent period of stability and peneplanation, incipient building of the modern Tien Shan orogen in Northern Kyrgyzstan started in the Oligocene according to our data. Intense basement cooling in distinct reactivated and fault-controlled sections of the Trans-Ili and Terskey Ranges finally pinpoint important Miocene–Pliocene (~22–5Ma) exhumation of the Issyk-Kul basement. Late Cenozoic formation of the Tien Shan is associated with ongoing indentation of India into Eurasia and is a quintessential driving force for the reactivation of the entire Central Asian Orogenic Belt.

Structural control on Meso-Cenozoic tectonic reactivation and denudation in the Siberian Altai: Insights from multi-method thermochronometry

The Siberian Altai forms part of the Central Asian Orogenic Belt and currently is an active intracontinental mountain belt. This Siberian Altai orogen was shaped during multiple phases of intense mountain building and associated denudation throughout the Mesozoic and Cenozoic. We performed a multi-method thermochronometric study on the Altai basement in Siberia in order to distinguish these denudation episodes and to place them in an absolute time-frame. Our data shows that inherited suture zones, such as the Charysh–Terekta–Ulagan–Sayan suture, played a dominant role during this episodic deformation in the Altai. Titanite fission track results reveal Late Triassic–Early Jurassic cooling, which is best expressed in intrusions close to the suture zone. Apatite fission track (AFT) results reveal a second phase of steady basement cooling during the Late Jurassic and Cretaceous. In the suture, AFT and additional apatite (U–Th–Sm)/He (AHe) data reveal a consistent Late Cretaceous–Early Palaeogene phase of fast cooling. We interpret the Mesozoic cooling signals as far-field effects of the Mongol-Okhotsk orogeny. The intense Late Cretaceous–Palaeogene basement cooling signal in the suture zone can be explained as a result of fault-reactivation during the collapse of this orogen and the subsequent re-organization of crustal blocks. During most of the Palaeogene and Early Neogene, basement cooling stagnated, indicating tectonic quiescence. Neogene AHe ages for the Kurai Range, directly adjacent to the suture may reflect renewed rapid cooling as a result of denudation of the present-day Altai mountains. We interpret this most recent cooling as an indirect consequence of stress-propagation from the India–Eurasia collision into the CAOB interior, which thus reached as far as southern Siberia. This study further demonstrates the importance of thermochrological studies on intrusions along major fault-zones in order to date and distinguish fault-reactivation episodes.

Tectonic history of the Kyrgyz South Tien Shan (Atbashi‐Inylchek) suture zone: The role of inherited structures during deformation‐propagation

Multimethod chronology was applied on intrusives bordering the Kyrgyz South Tien Shan suture (STSs) to decipher the timing of (1) formation and amalgamation of the suturing units and (2) intracontinental deformation that built the bordering mountain ranges. Zircon U/Pb data indicate similarities between the Tien Shan and Tarim Precambrian crust. Caledonian (∼440–410 Ma) and Hercynian (∼310–280 Ma) zircon U/Pb ages were found at the edge of the STSs, related to subduction and closure of the Turkestan Ocean and the formation of the suture itself. Permian‐Triassic (∼280–210 Ma) titanite fission track and zircon (U‐Th)/He data record the first signs of exhumation when the STSs evolved into a shear zone and the adjacent Tarim basin started to subside. Low‐temperature thermochronological (apatite fission track, zircon and apatite (U‐Th)/He) analyses reveal three distinct cooling phases, becoming younger toward the STSs center: (1) Jurassic‐Cretaceous cooling ages provide evidence that a Mesozoic South Tien Shan orogen formed as a response to the Cimmerian orogeny; (2) Early Paleogene (∼60–45 Ma) data indicate a renewed pulse of STSs reactivation during the Early Cenozoic; (3) Neogene ages constrain the onset of the modern Tien Shan mountain building to the Late Oligocene (∼30–25 Ma), which intensified during the Miocene (∼10–8 Ma) and Pliocene (∼3–2 Ma). The Cenozoic signals may reflect renewed responses to collisions at the southern Eurasian border (i.e., the Kohistan‐Dras and India‐Eurasia collisions). This progressive rejuvenation of the STSs demonstrates that deformation has not migrated steadily into the forelands, but was focused on pre‐existing basement structures.

Emplacement and exhumation of the Kuznetsk‐Alatau basement (Siberia): implications for the tectonic evolution of the Central Asian Orogenic Belt and sediment supply to the Kuznetsk, Minusa and West Siberian Basins

Terra Nova, 23, 248–256, 2011AbstractNew geochronological data [zircon U/Pb, titanite fission‐track (TFT) and apatite fission‐track (AFT) dating and apatite (U‐Th‐Sm)/He thermochronology] and thermal history modelling yield constraints on the development of the granitoid basement of the Kuznetsk‐Alatau Mountains, southern Siberia. The final stages of magmatism in the Kuznetsk‐Alatau palaeo‐island‐arc are Late Cambrian, and collision of the arc with Siberia occurred in the Early Ordovician. The basement was exhumed by the Early Devonian. Continuous Devonian–Early Triassic sedimentation filled the adjoining Kuznetsk and Minusa basins and buried (and re‐heated) the Kuznetsk‐Alatau basement. After initial Pangaea break‐up and Siberian flood‐basalt magmatism, the basement reached TFT and AFT retention‐temperatures in the Middle Triassic and Early Cretaceous, respectively, during denudation‐induced cooling.Terra Nova, 00, 1–9, 2011

Post Pan-African thermo-tectonic evolution of the north Mozambican basement and its implication for the Gondwana rifting. Inferences from 40 Ar/ 39 Ar hornblende, biotite and titanite fission-track dating

Abstract This research paper investigates the thermo-tectonic history of the north Mozambican basement subsequent to the Pan-African metamorphism. Six 40 Ar/ 39 Ar hornblende, three 40 Ar/ 39 Ar biotite and 25 titanite fission-track data place new constraints on the earliest timing of rifting in the central sector of Gondwana, and demonstrate a close linkage between the geometric rift configuration and the ductile metamorphic basement fabrics during the initial dispersal of the supercontinent. The 40 Ar/ 39 Ar hornblende and biotite ages range from c . 542 to 456 Ma and from c . 448 to 428 Ma, respectively. These data record slow basement cooling after the latest Pan-African metamorphism at rates of c . 7–11 °C Ma −1 between Early and Late Ordovician times. Locally, syn- to post-tectonic granitoid emplacements around 500–450 Ma delayed basement cooling to Late Ordovician–Early Silurian times. The titanite fission-track (TFT) ages fall into two age groups of c . 378–327 Ma and c . 284–219 Ma. The older TFT ages record very slow cooling from the Late Ordovician–Early Silurian to below 275±25 °C in the Late Devonian–Early Carboniferous at slow rates of less than 1 °C Ma −1 . This slow cooling is related to decreasing denudation in association with the establishment of pre-Karoo peneplains in central Gondwana. The younger TFT ages record denudation due to rift flank uplift in the context of initial Gondwana disintegration in the Mozambican sector. Corresponding Early–Late Permian crustal extension proceeded obliquely to a NW–SE tensional palaeo-stress field and was associated with a brittle reactivation of easterly trending ductile basement fabrics. In total, up to ≤9–12 km of denudation is deduced from the TFT results since Permo-Carboniferous times.

Transantarctic Basin: new insights from fission track and structural data from the USARP Mountains and adjacent areas (Northern Victoria Land, Antarctica)

ABSTRACTThe USARP Mountains comprise two N–S‐aligned mountain ranges (Daniels Range, Pomerantz Tableland) located along the western margin of the Rennick Glacier in Northern Victoria Land (NVL). Four zircon and titanite fission track (FT) ages from granitic samples from the Pomerantz Tableland fall in a common range of 369–392 Ma. The apatite FT ages from 20 Granite Harbour Intrusive rocks sampled throughout the USARP Mountains are distinctively younger (86–270 Ma); their mean track lengths (MTL) vary between 11.0 and 13.9 μm. Six samples from Renirie Rocks and the Kavrayskiy Hills east of the USARP Mountains have even younger, concordant apatite FT ages of 43–71 Ma, and MTL of 12.2–14.0 μm. Thermal history modelling of the thermochronological data indicate that both the Daniels Range and Pomerantz Tableland experienced a common Phanerozoic geologic history consisting of a mid‐Devonian pulse of rapid denudation, followed by a protracted denudation stage between the Carboniferous and Jurassic. This latter period of denudation was contemporaneous with the formation of the Transantarctic Basin to the east. We consequently suggest that the USARP Mountains were one of the major source areas for the Beacon Supergroup that formed the fill of the Transantarctic Basin. Subsequent to the deposition of the Beacon sequence, the now‐outcropping rocks of the USARP Mountains were buried to a maximum depth of 4.2 km. A palaeogeothermal gradient of 25±8°C km−1 was inferred at the time of maximum burial. Inversion of the Transantarctic Basin due to the breakup of Gondwana, and in response to Cenozoic rifting and uplift of the Transantarctic Mountains, has triggered the final denudation stages recorded in NVL since the Cretaceous. Thereby, the amounts of denudation increase eastward. Whereas 2.4–4.2 km of crustal unloading are recognized for the USARP Mountains since the Cretaceous, more than 4 km of denudation has occurred towards the Rennick Graben alone since the Eocene. This denudation was associated with major fault activities involving early ENE–WSW to E–W‐directed extension. Related structures were reactivated by dominant NW–SE to NNW–SSE‐oriented right‐lateral shear genetically linked to the formation and inversion of the structural depression of the Rennick Graben in Cenozoic times.

Phanerozoic upper crustal tectono-thermal development of basement rocks from central Madagascar: An integrated fission-track and structural study

An integrated study of fission-track (FT) dating and structural geology revealed a complex tectono-thermal history preserved in basement rocks of central Madagascar since the amalgamation of Gondwana at the end of the Cambrian. A detailed study of five domains argues for several cooling steps with associated brittle deformations during the separation of Madagascar. Titanite and apatite FT ages range between 483 Ma and 266 Ma and between 460 Ma and 79 Ma, respectively. The titanite FT data indicate that the final cooling after the latest metamorphic overprint was terminated at c. 500 Ma (FC1). A 150 Myr phase of minor cooling (SC2), possibly related to a phase of tectonic quiescence and isostatic compensation, followed episode FC1. Between the Carboniferous and Early Jurassic, when an intracontinental rift developed between East Africa and Madagascar, complex brittle deformation effected the western margin of Madagascar and led to differential cooling of small basement blocks (FC3–FC5). During this period, ductile structural trends were reactivated at the western basement margin and in the centre of the island. A Late Cretaceous thermal event (T1) affected apatite FT data of samples from western–central and the eastern margin of Madagascar. These ages are related to the Madagascar–India/Seychelles break-up, whereby the thermal penetration along the eastern coast was restricted to the west by the Angavo shear zone (AGSZ). The Cretaceous evolution of the eastern margin was associated with minor erosion and was triggered by vertical displacements along brittle structures.

Titanite and apatite fission track analyses on basement rocks of central-southern Madagascar: constraints on exhumation and denudation rates along the eastern rift shoulder of the Morondava basin

Titanite and apatite fission-track (FT) thermochronology from basement rocks in central-southern Madagascar reveals a protracted post Late Neoproterozoic/Early Cambrian history of extensional tectonism, denudation and sedimentation. Titanite FT ages range between 379 ± 38 and 276 ± 17 Ma and apatite FT ages vary between 379 ± 19 and 150 ± 8 Ma. Combined titanite and apatite FT data from the western palaeo margin of Madagascar suggest denudation rates of ∼200–100 mMa −1 during Carboniferous times. The Late Neoproterozoic/Early Cambrian Ejeda shear zone was probably reactivated during this time. In contrast, for the same period denudation rates inland are ∼110–25 mMa −1. During Permo-Triassic rifting, areas that previously underwent fast denudation were buried by sedimentary cover up to ∼4.5 km. At this time, a graben developed along the transcontinental Bongolava–Ranotsara shear zone (BRSZ). Graben faults are exposed at the northeastern graben shoulder. Identical titanite and apatite FT ages close to the BRSZ indicate rapid cooling associated with fluid circulation during Early Permian times. The initial Gondwana break-up during Middle Jurassic times and the drift of Madagascar along the Davie transform fault did not significantly influence the FT data and had only minor geomorphic impact in the study area. Only the far southwestern part of the island is characterised by a higher degree of denudation (max. ∼3.5 km) during Early Jurassic times. Early Cretaceous and Cenozoic volcanic activity affected the apatite FT data from southern Madagascar. Modelled time–temperature ( T– t) paths argue for a reheating of samples from southern Madagascar to temperatures of ∼60–80 °C during the times of magmatism, before final cooling to surface temperatures.

A titanite fission track profile across the southeastern Archæan Kaapvaal Craton and the Mesoproterozoic Natal Metamorphic Province, South Africa: evidence for differential cryptic Meso- to Neoproterozoic tectonism

Titanite fission track data are presented from samples taken at regular intervals along a ∼ 250 km long traverse from the ca 1.1 Ga Natal Metamorphic Province into the Archæan Kaapvaal Craton, southeastern South Africa. The titanite fission track traverse was intended to distinguish any differences in low-temperature (280°C) cooling trajectories between the two provinces and to identify, so far unrecorded, exhumation events. Titanite fission track age data in four groupings were obtained, namely at 1100 ± 200, 670 ± 100, 520 ± 50 and 170 ± 15 Ma. In addition to these main groupings, the older group contains a few single-grain ages of Palæoproterozoic age in the northernmost craton sample, from near Piet Retief. Samples from the craton, and the northernmost sample from the Natal Metamorphic Province, show a concentration of Grenville age ( ca 1100 Ma) single-grain ages. They reveal a cooling event that indicates that the craton margin was affected during the Mesoproterozoic to a larger extent then previously thought. Possibly, the dates reflect the timing of differential uplift of the rigid craton in response to loading by the over-thrusting of the Tugela nappes some 200 km to the south during the Mesoproterozoic collision event of the Natal Metamorphic Province. Alternatively, the data may suggest that the Tugela nappes extended far further north than previously thought, and the dates represent uplift from their unroofing. The age group of 670 ± 100 Ma is interpreted to represent mixed ages, with some titanite grains having predominantly Grenville-age age components and others having mainly Pan-African age components. Generally, the intensity of Pan-African overprint increases to the south and east. The southern craton samples and all samples from the Natal Metamorphic Province show a concentration of Pan-African single-grain ages of ca 520 ± 50 Ma. These dates are considered to represent fairly rapid uplift of the western foreland during the Pan-African collision of East and West Gondwana, which took place far to the east. Finally, samples taken from the northeastern part of the traverse give Jurassic dates, taken to represent thermal resetting during the Karoo volcanic event as a result of the break-up of Gondwana. The titanite fission track data presented thus aim to demonstrate the power of medium- to low-closure temperature geochronometer to reveal and distinguish younger, largely unseen but nevertheless important, tectonic events.

Pan-African rejuvenation of the c. 1.1 Ga Natal Metamorphic Province(South Africa):K–Ar muscovite and titanite fission track evidence

K–Ar muscovite and titanite fission track analyses were obtained from selected lithologies from the Grenville-aged ( c. 1.1 Ga) Natal Metamorphic Province, SE Africa in order to constrain the low temperature cooling history of this critical part of Gondwana. The data revealed two periods of basement rejuvenation and exhumation at c. 900 Ma and c. 530 Ma respectively. Over large areas of the Natal Metamorphic Province, late-stage skeletal muscovite, dated at c. 900 Ma. has overgrown the regional Mesoproterozoic fabrics. This indicates that, after magmatism and tectonics ceased at c. 1000 Ma. The Natal Metamorphic Province underwent an early Neoproterozoic thermal/hydration event. Titanite fission track dates from the southern Natal Metamorphic Province scatter around 530Ma. showing that the basement finally cooled fairly rapidly through the300°C isotherm during Pan-African times. Since the Natal Metamorphic Province is unconformably overlain by clastic sedimentary rocks dated at c. 490 Ma. The basement must have been uplifted and exhumed by c. 6–10km during the Pan-African event.Two possible uplift processes might best account for this Pan-African exhumation: Pan-African crustal thickening and subsequent uplift during the collision of east-and west-Protogondwana or magmatic underplating from hot mantle plumes. Although a combined collision-plume model cannot be discounted for western Dronning Maud Land, the Natal data favour the collision model, so it is proposed that the wider ‘Mozambique Belt’ of East Africa and East Antarctica generally resulted from classical Wison-cycle processes.