Zircon (U-Th)/He thermochronometry: He diffusion and comparisons with 40Ar/39Ar dating

Reiners, Peter W.; Spell, Terry L.; Nicolescu, Stefan; Zanetti, Kathleen A.

doi:10.1016/j.gca.2003.10.021

Cited by 646 publications

(575 citation statements)

References 76 publications

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“…The effective closure temperature of any sample depends on the cooling rate, grain size, mineralogy, and radiation damage (e.g., Farley, 2000; Flowers et al, 2009; Reiners et al, 2004, 2005). For this study, we collected 38 bedrock samples between ~18.5°S and 22.5°S along the fore arc of northern Chile, directly south of the Arica bend where a lack of thermochronometric data exist in previous literature (Figure 2a).…”

Section: Bedrock Thermochronometrymentioning

confidence: 99%

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

2018

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We present a regional analysis of new low‐temperature thermochronometer ages from the Central Andean fore arc to provide insights into the exhumation history of the western Andean margin. To derive exhumation rates over 10 million‐year timescales, 38 new apatite and zircon (U‐Th)/He ages were analyzed along six ~500‐km long near‐equal‐elevation, coast parallel, transects in the Coastal Cordillera (CC) and higher‐elevation Precordillera (PC) of the northern Chilean Andes between latitudes 18.5°S and 22.5°S. These transects were augmented with age‐elevation profiles where possible. Results are synthesized with previously published thermochronometric data, corroborating a previously observed trenchward increase in cooling ages in Peru and northern Chile. One‐dimensional thermal‐kinematic modeling of all available multichronometer equal‐elevation samples reveals mean exhumation rates of <0.2 km/Myr since ~50 Ma in the PC and ~100 Ma in the CC. Regression of pseudovertical age‐elevation transects in the CC yields comparable rates of ~0.05 to ~0.12 km/Myr between ~40 and 80 Ma. Differences between the long‐term mean 1‐D rates and shorter‐term age‐elevation‐derived rates indicate low variability in the exhumation history. Modeling results suggest similar background exhumation rates in the CC and PC; younger ages in the PC are largely a function of increased heat flow and consequently an elevated geothermal gradient near the arc. Slow exhumation rates are suggestive of semiarid conditions across the region since at least the Eocene and deformation and development of the Andean fore arc around this time.

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Section: Bedrock Thermochronometrymentioning

confidence: 99%

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

2018

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“…During this event, the Karacabey Pluton must have been subjected to the temperatures of over 200°C because zircons from the granitoid have been reset for (U/Th)-He system, suggesting burial to depths of over 5-6 km's. The fourth pathway is between Early Jurassic deposition and the Zr (U/Th)-He ages, indicating cooling to temperatures of 170-190°C (Reiners et al, 2004). After resetting Zr (U/Th)-He ages during post-Jurassic burial, blocking of the Zr (U/Th)-He ages occurred during the Late Cretaceous (Turonian) possibly related to uplift and erosion.…”

Section: Thermal History Of the Regionmentioning

confidence: 99%

Devonian magmatism in the western Sakarya Zone, Karacabey region, NW Turkey

Sunal

2012

Geodinamica Acta

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The Karacabey Pluton is a large magmatic body in the northwestern Turkey overthrust by the probable Triassic metamorphic rocks of the Lower Karakaya Complex. Both the metamorphic rocks and the Karacabey Pluton are unconformably overlain by a Lower Jurassic and younger sedimentary sequence. The Karacabey Pluton was regarded as a Carboniferous intrusion based on the previous K-Ar biotite geochronological data. Here, we provide new geological, geochemical and geochronological data from the Karacabey Pluton. Zircon U-Pb results from two samples yielded ages of 393.8 +/−2.7 to 395.9 +/−4.09 Ma, suggesting that the granitoids intruded in the crust throughout the Early to Middle Devonian. The Karacabey Pluton consists mainly of biotite and locally hornblende bearing granitoid with lesser amounts of S-type leucocratic granodiorite, all of which are cut by pegmatitic bodies. It belongs to the high-K calc-alkaline series with distinct Nb and Ta anomalies in multi-element spider diagram. Sr and Nd isotopes' initial values are 0.709-0.712 and 0.511-0.512, respectively. εNd(i) values range between −7.8 and −9.4. The isotopic characteristics of the rocks indicate lower crustal sources of both metapelitic and metaigneous origin. Geochemical features of the rocks suggest that they developed in an arc-related environment, along with the other Devonian granitoids described from the Biga Peninsula in northwest Turkey. The granitoid shows a low-temperature alteration/metamorphism marked by recrystallization of quartz, sericitization of the feldspar and formation of late chlorite, epidote and muscovite. Possibly because of these, the Ar-Ar biotite ages are scattered with a possible concentration at around Permo-Carboniferous boundary. Zircon (U-Th)/He geochronology suggests that after the granitoid was reburied during Early Jurassic to Early Cretaceous sedimentation, there was renewed uplift and erosion during the Late Cretaceous (Turonian), which is possibly related to the closure of the Intra-Pontide Ocean in the north.Keywords: Karacabey Pluton; Sakarya Zone; geochemistry; zircon U-Pb, biotite Ar-Ar and zircon (U-Th)/He ages IntroductionThe Sakarya Zone of the Pontides is an E-W trending belt bounded by Istanbul Zone in the north and by the Izmir-Ankara Suture in the south (Figures 1 and 2). It consists of a complex basement overlain by Jurassic and younger sedimentary sequence. The basement rocks of the Sakarya Zone can be divided into two separate parts: 1. Paleozoic plutonic and metamorphic rocks possibly related to the Variscan orogeny and 2. Triassic accretionary complexes with blueschists and eclogites, called as the Karakaya Complex (Okay & Göncüoğlu, 2004;Okay & Tüysüz, 1999;Okay, Satır & Siebel, 2006).Most of the plutonic rocks in the basement of the Sakarya Zone are of Carboniferous age (350-320 Ma, Figure 1). These can traced from the Kazdağ Massif in the Biga peninsula (308-329 Ma, Okay et al., 1996, through west of Ankara (~290 Ma, Okay et al., 2006, 319-327 Ma;Robertson, 2012) and Central Pontides (275-295 Ma, Nzeg...

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“…[8] U-Th/He ages of zircon and apatite were measured at Yale University on single-grain aliquots using standard procedures involving laser heating and cryogenically processed He analysis on a gas source mass spectrometer, followed by HR-ICP-MS measurement of parent nuclides, as described in the work by Reiners et al [2004] and Reiners [2005].…”

Section: Analytical Techniquesmentioning

confidence: 99%

Thermochronology of the Talkeetna intraoceanic arc of Alaska: Ar/Ar, U‐Th/He, Sm‐Nd, and Lu‐Hf dating

et al. 2011

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[1] As one of two well-exposed intraoceanic arcs, the Talkeetna arc of Alaska affords an opportunity to understand processes deep within arcs. This study reports new Lu-Hf and Sm-Nd garnet ages, 40 Ar/ 39 Ar hornblende, mica and whole-rock ages, and U-Th/He zircon and apatite ages from the Chugach Mountains, Talkeetna Mountains, and Alaska Peninsula, which, in conjunction with existing geochronology, constrain the thermal history of the arc. The oldest U-Th/He zircon ages are ∼137 to 129 Ma, indicating no Cenozoic regional heating above ∼180°C. Although the signal is likely complicated by Cretaceous and Oligocene postarc magmatism, the aggregate thermochronology record indicates that the thermal history of the Talkeetna arc was spatially variable. Onedimensional finite difference thermal models show that this kind of spatial variability is inherent to intraoceanic arcs with simple construction histories. Citation: Hacker,

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Zircon (U-Th)/He thermochronometry: He diffusion and comparisons with 40Ar/39Ar dating

Cited by 646 publications

References 76 publications

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

Devonian magmatism in the western Sakarya Zone, Karacabey region, NW Turkey

Thermochronology of the Talkeetna intraoceanic arc of Alaska: Ar/Ar, U‐Th/He, Sm‐Nd, and Lu‐Hf dating

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