Apatite Fission Track Data Research Articles

Free Radicals in Organic Matter for Thermal History Reconstruction of Carbonate Succession

Abstract: Geothermometer is one of the most useful methods to reconstruct the thermal history of sedimentary basins. This paper introduces the application of free radicals concentration of organic matter as a thermal indicator in the thermal history reconstruction of carbonate succession, based on anhydrous thermal simulation results of type I and II1 kerogen. A series of free radicals data are obtained under thermal simulation of different heating temperatures and times, and quantitative models between free radical concentration (Ng) of organic matter and time‐temperature index (TTI) for types I and type II1 kerogen are also obtained. This Ng‐TTI relation was used to model the Ordovician thermal gradients of Well TZ12 in the Tarim Basin. The modeling result is corresponding to the results obtained by apatite fission track data and published data. This new method of thermal history reconstruction will be benefit to the hydrocarbon generation and accumulation study and resource assessment of carbonate succession.

Provenance of Cretaceous clastics in the Subhercynian Basin: constraints to exhumation of the Harz Mountains and timing of inversion tectonics in Central Europe

The Harz Mountains and the adjacent Subhercynian Cretaceous Basin figure as the most prominent surface representative for Late Cretaceous inversion structures in Central Europe. Facies, depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the Harz. From Hauterivian to Early Santonian there is no evidence for detrital input from the nearby Harz area. Sediments are mature quartzarenites derived from Paleozoic basement rocks and/or recycled Permian to Mesozoic sedimentary rocks. This situation changed drastically in Middle to Late Santonian when freshly exhumed and eroded Mesozoic sedimentary cover rocks of the Harz were delivered into the basin. Feldspar and lithoclasts reflect erosion of Triassic and, in places, Jurassic to Turonian strata. Apatite and garnet in heavy mineral spectra are derived from largely unweathered Lower Triassic Buntsandstein as indicated by apatite and garnet chemistry. In Early Campanian, Paleozoic lithoclasts indicate erosion cutting down into the basement of the Harz. Simultaneous strong decrease of feldspar, garnet and apatite suggest an almost complete removal of the 2–3 km thick Mesozoic cover of the Harz within only 2–4 Myr. This translates into an exhumation rate of approximately 1 mm/a consistent with apatite fission track data from granitoid rocks of the Harz Mountains.

Mesozoic to Quaternary continental margin dynamics in South-Central Chile (36–42°S): the apatite and zircon fission track perspective

Zircon and apatite fission track data provide constraints on the exhumation history, fault activity, and thermal evolution of the South-Central Chilean active continental margin (36°S–42°S), which we use to assess the tectonic and geomorphic response of the margin to the Andean subduction regime. Several domains with different exhumation histories are identified. The Coastal Cordillera is characterized by uniform and coherent exhumation between Late Triassic (∼200 Ma) and late Miocene times, with surprisingly slow average rates of 0.03–0.04 mm/a. Thermal anomalies, related to Late Cretaceous and early Miocene magmatism, have regionally modified fission track age patterns. The Upper Cretaceous thermal overprint is of previously unrecognized significance and extent in the Coastal Cordillera south of 39°S. With the exception of a local but distinct Pliocene to Recent exhumation period in the high-relief Cordillera Nahuelbuta segment between 37°S and 38°S, Cenozoic overall exhumation in the Coastal Cordillera was very slow. The sedimentary record shows that uplift and subsidence here was episodic, with low amplitudes and durations. This rules out large-scale, long-term, Cenozoic accretion, trench-parallel tilting, and tectonic erosion processes in the forearc. The Main Andean Cordillera shows markedly greater long-term exhumation rates than the Coastal Cordillera and, at ∼39°S, a steep exhumation gradient. To the south, long-term average Pliocene to Recent exhumation rates of ∼1 to ∼2 mm/a in the Liquine area (39°45′S) are almost an order of magnitude more rapid than average Paleogene to Recent exhumation near Lonquimay (38°30′S) and farther north. While no imprint of the intra-arc Liquine-Ofqui Fault Zone on the exhumation pattern is evident, long-term exhumation rates decrease from the crest of the Andes toward the western foothills. Exhumation gradients correlate with climatic gradients, suggesting a causal link to the variable intensity of late Miocene to Pleistocene glacial erosion.

Apatite fission track data from central Anatolian granitoids (Turkey): Constraints on Neo‐Tethyan closure

Apatite fission track age versus elevation profiles and temperature‐time‐path modeling indicate an early to middle Paleocene (57–62 Ma) rapid exhumation of the Middle to Late Cretaceous granitoids in central Anatolia and an Oligocene (28–30 Ma) rapid exhumation of the Eocene Kösedağ batholith in the NE Sivas region, part of eastern central Pontides. The early to middle Paleocene rapid exhumation is thought to result from a regional compressional regime following the collision of the Eurasian Plate and the Tauride‐Anatolide Platform at the closure of the Izmir‐Ankara‐Erzincan branch of the northern Neo‐Tethys. The Oligocene accelerated exhumation of the Kösedağ batholith is contemporaneous with the Oligo‐Miocene closure of the southern Neo‐Tethys which juxtaposed the amalgamated Eurasian and Tauride‐Anatolide Platform and the African‐Arabian Plate along the Bitlis‐Zagros suture in southeast Anatolia. The compressional regime due to this collision affected a large area between the Greater Caucasus in the north and northern African‐Arabian Plate in the south.

Plio‐Quaternary exhumation history of the central Nepalese Himalaya: 2. Thermokinematic and thermochronometer age prediction model

In the Himalaya and other active convergent orogens, linear relationships between thermochronometer sample age and elevation are often used to estimate long‐term exhumation rates. In these regions, high‐relief topography and nonvertical exhumation pathways may invalidate such one‐dimensional (1‐D) interpretations and lead to significant errors. To quantify these errors, we integrate apatite fission track (AFT) ages from the central Himalaya with a 3‐D coupled thermokinematic model, from which sample cooling ages are predicted using a cooling‐rate‐dependent algorithm. By changing the slip partitioning between faults near the Main Central thrust and the Main Frontal thrust system at the Himalayan range front, we are able to explore the significance of different tectonic scenarios on predicted thermochronometer ages. We find that the predicted AFT cooling ages are not sensitive to the different slip partitioning scenarios but depend strongly on erosion rate: Predicted ages are most consistent with kinematic models that produce erosion rates of 1.8–5.0 mm/yr. This range is considerably smaller than that derived from regression lines through the data (−2.6–12.2 mm/yr). The pattern of observed AFT ages shows more complexity than our models predict. None of the kinematic scenarios are able to fit >80% of all of the AFT data, most likely because erosion is spatially variable. Such complexities notwithstanding, we conclude that the use of thermokinematic modeling and thermochronologic data sets to explore detailed fault kinematics in rapidly eroding active orogens has great promise but requires integration of higher‐temperature (>∼350°C) data sets to maximize effectiveness.

Quantitative and qualitative insights into bedrock landform erosion on the South Indian craton using cosmogenic nuclides and apatite fission tracks

Research Article| May 01, 2007 Quantitative and qualitative insights into bedrock landform erosion on the South Indian craton using cosmogenic nuclides and apatite fission tracks Y. Gunnell; Y. Gunnell 1Department of Geography, Université Denis-Diderot Paris 7, case 7001, 2 Place Jussieu, 75251 Paris cedex 05, France Search for other works by this author on: GSW Google Scholar R. Braucher; R. Braucher 2Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, UMR 6635, Europôle Méditerranéen de l'Arbois, BP 80, 13545 Aix-en-Provence cedex 04, France Search for other works by this author on: GSW Google Scholar D. Bourlès; D. Bourlès 2Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, UMR 6635, Europôle Méditerranéen de l'Arbois, BP 80, 13545 Aix-en-Provence cedex 04, France Search for other works by this author on: GSW Google Scholar G. André G. André 3Department of Geography, Université Denis-Diderot Paris 7, case 7001, 2 Place Jussieu, 75251 Paris cedex 05, France Search for other works by this author on: GSW Google Scholar Author and Article Information Y. Gunnell 1Department of Geography, Université Denis-Diderot Paris 7, case 7001, 2 Place Jussieu, 75251 Paris cedex 05, France R. Braucher 2Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, UMR 6635, Europôle Méditerranéen de l'Arbois, BP 80, 13545 Aix-en-Provence cedex 04, France D. Bourlès 2Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, UMR 6635, Europôle Méditerranéen de l'Arbois, BP 80, 13545 Aix-en-Provence cedex 04, France G. André 3Department of Geography, Université Denis-Diderot Paris 7, case 7001, 2 Place Jussieu, 75251 Paris cedex 05, France Publisher: Geological Society of America Received: 02 Dec 2005 Revision Received: 17 Sep 2006 Accepted: 11 Jan 2007 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 GEOLOGICAL SOCIETY OF AMERICA GSA Bulletin (2007) 119 (5-6): 576–585. https://doi.org/10.1130/B25945.1 Article history Received: 02 Dec 2005 Revision Received: 17 Sep 2006 Accepted: 11 Jan 2007 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Y. Gunnell, R. Braucher, D. Bourlès, G. André; Quantitative and qualitative insights into bedrock landform erosion on the South Indian craton using cosmogenic nuclides and apatite fission tracks. GSA Bulletin 2007;; 119 (5-6): 576–585. doi: https://doi.org/10.1130/B25945.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Due to the scarcity of datable chronostrati-graphic markers and the related difficulties of quantifying depths of erosion in cratonic landscapes, conceptual models of tropical pediplain and etchplain evolution commonly lack time and vertical elevation scales. Here, we present the first quantitative study of relief development in South India based on in situ–produced 10Be dating aided by previously acquired apatite fission-track data. Erosion rates measured on the summits of inselbergs concur with the perception of inselbergs as islands of low erosion, but they also reveal a critical contrast between slowly evolving (≤2 m/m.y.) higher-relief landforms and more rapidly eroding (8–12 m/m.y.) lower-relief landforms. This relationship is independent of lithology and climate but suggests that erosion rates on the surrounding plain, which are controlled by fluvial incision rates into the plateau surface, feed back on inselberg dynamism. A discussion on the most suitable sites for dating bedrock land-forms highlights the problems of sampling design, the difficulties of linking measured erosion rates to the minutiae of process, and the limitations of both single- and multiple-chronometer denudation chronologies in low-energy cratonic environments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Thermal history of the Vestfold Hills (East Antarctica) between Lambert rifting and Gondwana break-up, evidence from apatite fission track data

Analysis of five basement samples from the Vestfold Hills (East Antarctica) reveals pooled apatite fission track (FT) ages ranging from 188 to 264 Ma and mean lengths of 13.7 to 14.9 μm. Quantitative thermal histories derived from these data give consistent results indicating onset of cooling/denudation began sometime prior to 240 Ma, with final cooling below 105°–125°C occurring between 240 and 220 Ma (Triassic). A Cretaceous denudation phase can be inferred from the sedimentary record of the Prydz Bay offshore the Vestfold Hills. The two denudational episodes are likely associated with Palaeozoic large-scale rifting processes that led to the formation of the adjacent Lambert Graben, and to the Cretaceous Gondwana break-up between Antarctica and India. Subsequent evolution of the East Antarctic passive continental margin likely occurred throughout the Cenozoic based on the depositional record in Prydz Bay and constraints (though tentative) from FT data.

Tectonic controls on the late Miocene–Holocene volcanic eruptions of the Tengchong volcanic field along the southeastern margin of the Tibetan plateau

The Tengchong volcanic field, located along the southeastern margin of the Tibetan plateau, experienced multiple eruption stages since the late Miocene, including time intervals of ∼5.5–4.0 Ma, 3.9–0.9 Ma, 0.8–0.01 Ma, and younger than 0.01 Ma. These eruption stages produced different volcanic rocks, principally basaltic and basaltic-andesite series. At the same time or prior to volcanic eruptions in the Tengchong volcanic field, NE–NNE-trending rift basins and NS-striking normal faults formed during the late Miocene–Pliocene. In addition, rapid exhumation of the neighboring mountains occurred at ∼6–5 Ma constrained by apatite fission track dating and its thermochronological modeling. At present, the state of stress in the Tengchong volcanic field and its surroundings is NNE–NE-compression and WNW–NW-extension based on seismic foci mechanisms. Petrologic and geochemical data indicate that the source of the Tengchong volcanic rocks belongs to an intracontinental tectonic setting, but not a subduction or collision zone between Indian and Eurasian plates. Since the late Miocene, the dextral strike-slip motion of the Sagaing fault induced E–W-extension. The Sagaing dextral strike-slip motion might disturb the lower crust-upper mantle of the Tengchong block, resulting in the partial melting of the upper mantle which, in turn, induced volcanic eruptions characterized by mature island-arc features.

A report on fission-track data of zircon and apatite age-standards for age calibration using diallyl phthalate (DAP) resin detectors and a minor revision of zeta values by Danhara et al. (2003)

We re-determined zeta values for zircon and apatite fission track dating, using diallyl phthalate (DAP) detectors and the modified observation system with newly installed HAMAMATSU PHOTONICSTM digital CCD camera and TOUCH PANEL SYSTEMSTM monitor. To minimize the human exposure to radioactivity after the sample irradiation, S-DAP detector was tested for apatite analyses and compared to the Q-DAP detector. The resulting zeta values are: 385 ± 4 (ED1) and 352 ± 4 (ED2) for zircon combined with Q-DAP detectors, and 300 ± 4 (ED1) and 321 ± 4 (ED1) for apatite with S-DAP and Q-DAP detectors, respectively. Data of the Durango Apatite were excluded from zeta value calculation due to contribution of fast-neutron-induced tracks of Th in the sample.

Developing a Competitive Pearl River Delta in South China under One Country-Two Systems. Anthony Gar-on Yeh , Victor Fung-shuen Sit , Guanghan Chen , Yunyuan Zhou

Previous articleNext article No AccessReviewsDeveloping a Competitive Pearl River Delta in South China under One Country-Two Systems. Anthony Gar-on Yeh , Victor Fung-shuen Sit , Guanghan Chen , Yunyuan Zhou Fulong WuFulong Wu Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The China Journal Volume 57Jan., 2007 Published on behalf of the Australian Centre on China in the World at the Australian National University Article DOIhttps://doi.org/10.1086/tcj.57.20066253 Views: 9Total views on this site Citations: 15Citations are reported from Crossref Copyright The China JournalPDF download Crossref reports the following articles citing this article:Yinzhi Wang, Fei Wang, Lin Wu, Zhiyong Zhang, Wenbei Shi, Liekun Yang Differential post-mineralization thermal evolution of the Jiaodong and Liaodong Areas, Eastern China: An indicator of regional tectonic activity, Gondwana Research 103 (Mar 2022): 502–521.https://doi.org/10.1016/j.gr.2021.11.006Zhenwei Li, Chuanzhong Song, Jiahao Li, Peng Huang, Yangyang Wang, Fang Yuan, Wei Wang, Hailong Li Timing of deformation along the Tan‐Lu Fault Zone in eastern China: Constraints from zircon U–Pb geochronology of the Malongshan Shear Zone, Geological Journal 55, no.1212 (Jul 2020): 7916–7934.https://doi.org/10.1002/gj.3873Yutian Liang, Zhengke Zhou, Xun Li Dynamic of Regional Planning and Sustainable Development in the Pearl River Delta, China, Sustainability 11, no.2121 (Nov 2019): 6074.https://doi.org/10.3390/su11216074Wenjie Zhou, Rui Mu Exploring Coordinative Mechanisms for Environmental Governance in Guangdong-Hong Kong-Macao Greater Bay Area: An Ecology of Games Framework, Sustainability 11, no.1111 (Jun 2019): 3119.https://doi.org/10.3390/su11113119Changbo Li, Ren Jiang, Jianwei Zeng, Junjie Yu, Kai Liu, Bo Peng, Jinxiu Lao, Ling Zhao Deep structures underneath the Sihong Segment of the Tan-Lu Fault Zone, Eastern China: Interpretations of gravity anomaly and seismic profiles, Journal of Asian Earth Sciences 176 (Jun 2019): 229–243.https://doi.org/10.1016/j.jseaes.2019.02.014Jingsong PENG, Ajuan WEI, Zhe SUN, Xinlu CHEN, Dijiang ZHAO Sinistral strike slip of the Zhangjiakou-Penglai Fault and its control on hydrocarbon accumulation in the northeast of Shaleitian Bulge, Bohai Bay Basin, East China, Petroleum Exploration and Development 45, no.22 (Apr 2018): 215–226.https://doi.org/10.1016/S1876-3804(18)30025-9HongShui Tian, Antonius Johannes Van Loon, HuaLin Wang, ShenHe Zhang, JieWang Zhu Seismites in the Dasheng Group: New evidence of strong tectonic and earthquake activities of the Tanlu Fault Zone, Science China Earth Sciences 59, no.33 (Dec 2015): 601–618.https://doi.org/10.1007/s11430-015-5221-4LI Chunlin, WANG Zongxiu, WU Qingzi, LIU Yongqing, GAO Wanli, TAN Yuanlong, KUANG Hongwei, LI Huijun Late Cretaceous Transpressional Fault System: A Case Study of the Yishu Fault Belt, Shandong Province, Eastern China, Acta Geologica Sinica - English Edition 89, no.55 (Oct 2015): 1531–1545.https://doi.org/10.1111/1755-6724.12562Daqing TANG, Honghan CHEN, Tao JIANG, Hui ZHANG, Yuchao QIU, Li CHEN Neogene differential structural inversion and hydrocarbon accumulation in the Yitong Basin, NE China, Petroleum Exploration and Development 40, no.66 (Dec 2013): 731–741.https://doi.org/10.1016/S1876-3804(13)60098-1ZHANG Jiaodong, CHEN Xuanhua, LI Qiuli, LIU Chengzhai, LI Bing, LI Jie, LIU Gang, REN Fenglou Mesozoic “Red Beds” and its Evolution in the Hefei Basin, Acta Geologica Sinica - English Edition 86, no.55 (Oct 2012): 1060–1076.https://doi.org/10.1111/j.1755-6724.2012.00731.xBin WANG, Guowei ZHANG New Jurassic Paleomagnetic Results from Southeastern China and Their Geological Implication, Acta Geologica Sinica - English Edition 85, no.44 (Aug 2011): 792–800.https://doi.org/10.1111/j.1755-6724.2011.00485.xY.M. Zhang, X.X. Gu, L. Liu, S.Y. Dong, K. Li, B.H. Li, P.R. Lv Fluid inclusion and H–O isotope evidence for immiscibility during mineralization of the Yinan Au–Cu–Fe deposit, Shandong, China, Journal of Asian Earth Sciences 42, no.1-21-2 (Jul 2011): 83–96.https://doi.org/10.1016/j.jseaes.2011.04.011Guiting Hou, Yanxin Wang, K.R. Hari The Late Triassic and Late Jurassic stress fields and tectonic transmission of North China craton, Journal of Geodynamics 50, no.3-43-4 (Sep 2010): 318–324.https://doi.org/10.1016/j.jog.2009.11.007Yi Yan, Xiaoqiong Hu, Ge Lin, Weiliang Liu, Zhengjiang Song Detrital zircon and apatite fission track data in the Liaoxi basins: Implication to Meso-Cenozoic thermo-tectonic evolution of the northern margin of the North China Craton, Journal of Earth System Science 119, no.44 (Nov 2010): 541–551.https://doi.org/10.1007/s12040-010-0028-3Biao SONG, Xiufu QIAO Ages of Zircons from Basalt of Erdaogou Formation and Diabase Dyke Swarms in Northern Liaoning, Earth Science Frontiers 15, no.33 (May 2008): 250–262.https://doi.org/10.1016/S1872-5791(08)60067-6

Morphotectonic evolution of the central Kenya rift flanks: Implications for late Cenozoic environmental change in East Africa

The Kenya rift valley is the classic example of an active continental rift zone. We report the rift flank cooling history based on a combination of previous apatite fission track (AFT) and new (U-Th)/He (AHe) data. Our results corroborate the Late Cretaceous rapid cooling episode of continent-wide significance revealed previously by AFT dating. Post-Cretaceous cooling of the eastern rift flank was slow with net cooling of 3400 m in central Kenya. This timing also largely coincides with the uplift of the Western Rift flanks in Uganda and Congo and with the change toward drier conditions and grassland-dominated vegetation in East Africa. We propose that the regional morphotectonic evolution of the Kenyan rift flanks contributed to late Cenozoic environmental change in East Africa, thus superimposing a pronounced local effect on global climate change at that time.

Diachronous late-stage exhumation across the western Alpine arc: constraints from apatite fission-track thermochronology between the Pelvoux and Dora-Maira Massifs

We present new apatite fission-track (AFT) data from the central western Alps that confirm the synchronicity and high cooling rates during Latest Miocene–Pliocene final exhumation of the External Crystalline Massifs but also provide evidence for diachronous Neogene evolution along and across the internal arc. To the SE of the Pelvoux Massif, across the front of the internal arc (Penninic Frontal Thrust), the jump in AFT ages ( c . 22 Ma) and in final cooling rates is significantly larger than further north. This difference results from reversal of movement along a major Oligocene thrust. In its hanging wall, the western Briançonnais Zone provides a mean AFT age of c . 27 Ma, which is older than further north. Early cooling in the southern Briançonnais Zone would result from rapid erosion of the compressional fan structure built during the Oligocene. Across the entire Briançonnais and Piémont nappe stack, with the exception of the Dora-Maira Massif, AFT ages young eastward and span the entire Miocene, a period during which this structure underwent extension. Further north a reverse gradient with ages younging northwestward has been described, prompting the question of the asymmetry of the internal western Alpine arc during its late-stage tectonic and morphological evolution.

Apatite (U – Th)/He age constraints on the Mesozoic and Cenozoic evolution of the Bathurst region, New South Wales: evidence for antiquity of the continental drainage divide along a passive margin

The apatite (U – Th)/He and fission track thermochronometers are combined to constrain the Mesozoic and Cenozoic denudational history of the Bathurst region in New South Wales. New apatite (U – Th)/He ages across the continental drainage divide range from 83 ± 14 to 114 ± 18 Ma (±2σ), supporting the evidence from previously published apatite fission track (AFT) data that the region underwent a period of rapid denudation during the mid-Cretaceous. The apatite He-derived thermal histories constrain the amount of erosion in the area and suggest that spatial variations in denudation of the Bathurst Batholith correspond to three broad regions with different histories. The area of the continental drainage divide separates the eastern flank where denudation was rapid at 120 – 90 Ma, and >3 km of crust was removed in about 30 million years, from the western flank, where denudation was less rapid and less prominent. The coincidence of some of the AFT and He ages with the timing of continental extension and Tasman Sea opening suggests that the rapid denudation east of the continental drainage divide was associated with the rifting processes. Such an interpretation means that the escarpment that bounds the Blue Mountains on the east was not formed at the time of rifting and may be a later topographic feature, connected with exhumation of an earlier structural feature and/or related to post-Mesozoic tectonic activity. The evolution of the area west of the continental drainage divide is characterised by rates of denudation higher than on the rest of the plateau but lower than on the eastern flank in the Bathurst area. The reason for this pattern is still unclear. It is possible that faults of the Lachlan Fold Belt were reactivated during the Cretaceous extension and later, but no faults are mapped across the batholith. Overall, the data imply that the continental margin in the Bathurst region evolved by plateau downwearing pinned to the continental drainage divide. This means in turn that the continental drainage divide is a longstanding topographic feature, dating from before Tasman Sea breakup.

Scarp retreat versus pinned drainage divide in the formation of the Drakensberg escarpment, southern Africa

The dramatic escarpment bounding the Drakensberg-Maluti mountainland has long been regarded as a classic example of a topographic feature formed by scarp retreat processes. However, this view has recently been challenged on the basis of apatite fission track (AFT) and cosmogenic isotope data, which are argued to be inconsistent with a uniform rate of scarp retreat from the original position of continental break-up. It was suggested rather, that the evolution and present position of the escarpment was controlled primarily by a pre-existing inland drainage divide. Numeric surface process models have been used to support this interpretation, although these rely on a large number of unconstrained variables, and thus do not provide unique solutions. However, several lines of direct geological field evidence support the scarp retreat model for the evolution of the Drakensberg escarpment. The Drakensberg-Maluti Mountains in southern Africa are formed by a ~1000 m thick sequence of Karoo basalts, capping Karoo sediments. This mountainland has an approximately rectangular shape, surrounded by orthogonal escarpments, except in the southwest, where it is dissected by the deeply incised Orange River. In detail, these marginal scarps are everywhere double topographic features, reflecting two resistant layers that form prominent cliffs: the thick upper basalt flows, and the Clarens Formation sandstone at the base to the lava sequence. Moreover, in the Drakensberg-Maluti example, the presence of inland-facing escarpments reveals that escarpment formation is not exclusively related to processes that occur at or adjacent to the site of continental break-up. These direct geomorphological and geological observations demonstrate that resistant units are the dominant influence in escarpment formation. Headward retreat of large waterfalls on major rivers over considerable distances (10–100 km) provides clear field evidence that scarps formed by resistant lithologies will not invariably degrade as a result of the existence of an inland drainage divide, as has been argued on the basis of surface process modelling. Several complementary factors provide a ready explanation for apparent inconsistencies in the scarp retreat model that were identified from the AFT and cosmogenic isotope studies. The Drakensberg-Maluti mountains are surrounded by a dense network of dolerite dykes that were contemporary with, and supplied, the Karoo basalts. The massive lava flows capping the modern escarpment therefore probably originally extended at least to the edge of the dyke network. The advance inland of an erosion front, initiated by continental break-up, would have slowed dramatically where such massive lava flows were encountered. Tectonic processes, climate changes, and possibly plant evolution may have compounded this decrease in erosion rates. Although these latter factors are not readily quantified, they were probably subordinate to the dominant lithological control that we invoke. Escarpments may thus form and persist over long periods, extending from the time of continental break-up to the present, independently of inland drainage divides. These field observations must be taken into consideration when assigning values to the numerous unconstrained variables used in surface process models.

Fission Track Geochronology of Xiaonanchuan Pluton and the Morphotectonic Evolution of Eastern Kunlun since Late Miocene

ABSTRACT Apatite fission track (AFT) thermochronology of seven samples from the Xiaonanchuan ( ) pluton in the Kunlun ( ) pass area was carried out, for the purpose of determining the timing of cooling and the relation between the exhumation and the morphotectonic processes. The AFT ages yield low denudation rates of 0.020–0.035 mm/a during the late Miocene, which correspond to a stable geomorphic and weak tectonic uplifting environment. The low denudation rates can be considered as the approximate tectonic uplifting rates. The AFT geochronology shows paroxysmally rapid cooling since the Pliocene and an apparent material unroofing of more than 3 km in the Xiaonanchuan area. This was not the result of simple denudation. The rapid cooling was coupled with the intensive orogeny since the Pliocene, which was driven by tectonic uplifting. The accelerated relief building was accompanied by a series of faulting, which caused the basin and the valley formation and sinking. The space pattern of the AFT ages also shows differential uplifting, which decreases northwardly. This trend is supported by the regional AFT data, which indicate that the exhumation decreases northwardly in eastern Kunlun. This trend also exists in east-west orientation from the western Kunlun range to the eastern. The uplifting trend is also supported by geomorphic characteristics including the elevation and the relief differences as well as the distribution of the Late Cenozoic volcanism.

Cenozoic evolution of tectono-fluid and metallogenic process in Lanping Basin, western Yunnan Province, Southwest China: Constraints from apatite fission track data

Since the Mesozoic, abundant metal and salt deposits have been formed in the Lanping Basin, western Yunnan Province, Southwest China, constituting a well-known hydrothermal ore belt in China. Most of the deposits are meso-epithermal hydrothermal deposits. This paper preliminarily deals with the mineralization ages of hydrothermal deposits in the Lanping Basin by using the apatite fission track method, and integrates the spatial distribution of the deposits and their regional geological backgrounds, to give the preliminary viewpoints as follows: (1) the apatite fission track ages acquired range from 19.9 Ma to 52.8 Ma, much younger than those of their host strata, so they may be considered to be mineralization ages, which represent the late mineralization period; (2) the apatite fission track ages tend to become younger from the west to the middle of the basin, indicating that the latest evolution of tectono-fluid and/or metallogenic processes of the middle basin ended later than that in the west; (3) in the Paleogene, most of the Cu deposits were formed in the western part of the basin; (4) the major metallogenic processes occur between the Paleogene and the Neogene, because the eastern and western edges of the basin were subducted into and collided with its bilateral continental blocks, respectively, and the central fault was strongly activated, which led to the processes of large-scale ore-forming fluids, and their differentiation and transport because of the variation of their physical and chemical properties. Having been squeezed and uplifted, the Lanping Basin became an intermontane basin that contains many kinds of fluid traps resulting in the formation of different types of ore deposits (for example, Pb-Zn, Cu, Ag) of different scales in the middle of the basin. Simultaneously, the fluids with volatile elements such as Hg, Sb and As were transported upwards along the central fault system and diffused into its subordinate fractures, thus leading to the metallogenic processes of Hg, Sb and As in the eastern composite anticline of the Lanping Basin; (5) and later, these ore deposits experienced reformation and oxidization. To summarize, deep giant faults were active in the basin, and metallogenic processes were constrained by the evolution of tectono-fluids in the Lanping Basin. Simultaneously, the occurrence of the metallogenic processes made the nature of fluid and the structural environment change, which led to returning and recycling of the fluids. Multi-stage and zonational metallogenic processes are the characteristics of the ore deposits in the Lanping Basin.

The low-temperature thermal history of northern Switzerland as revealed by fission track analysis and inverse thermal modelling

New zircon and apatite fission track (FT) data from four boreholes, which penetrate the Mesozoic and pre-Mesozoic sediments and crystalline basement of northern Switzerland, are presented. Inverse thermal modelling of the measured apatite FT parameters unravels the low-temperature (below ~120°C) thermal history of the crystalline basement of northern Switzerland. Zircon FT central and single-grain ages cluster around 250 Ma, thus maximum palaeotemperatures did not exceed ∼ 330°C after late-Variscan consolidation of the crystalline basement. Apatite FT central ages vary between 25 and 87 Ma. Confined mean track lengths range between 9.3 μm and 11.6 μm, suggesting substantial track annealing within all apatite samples. Modelled time-temperature paths offer a clear picture about the low-temperature thermal history of the crystalline basement of northern Switzerland: Cretaceous cooling is followed by an Eocene heating event and subsequent cooling to present-day temperatures. The Eocene heating episode is contemporaneous with the initial rifting stage of the nearby Upper Rhine Graben and the associated increasing volcanic activity. Crustal-scale faults of the Permo-Carboniferous Trough of northern Switzerland could have acted as major pathways for circulating hydrothermal fluids giving rise to the observed Middle to Late Eocene thermal event.

Cooling history and tectonic exhumation stages of the south-central Tibetan Plateau (China): Constrained by 40Ar/ 39Ar and apatite fission track thermochronology

Between the Qiangtang Block and Yalung-Zangpo Suture Zone in the south-central Tibetan Plateau, the following geological units and suture zones have been identified from south to north: the Gangdese Granitic Belt, the Lhasa Block, the Nyainqentanghla Shear Zone, the Dangxiong–Sangxiong Tectono-granitic Belt and the Bangong–Nujiang Suture Zone. To better constrain the tectonic evolution and cooling histories of these units, 40Ar/ 39Ar muscovite, biotite and K-feldspar, as well as apatite fission track dating and thermochronological analysis have been carried out. The analytical results indicate that the south-central Tibetan Plateau, with the exception of the Nyainqentanghla Shear Zone, provides a record of three cooling stages at 165–150, 130–110 and ∼45–35 Ma. Fission-track data modelling also indicates that the stages of cooling were different in the different tectonic belts or blocks. Very different cooling phases occurred in the south-central Tibetan Plateau, compared with southern Tibet, as well as along the Yalung–Zangpo Suture Zone. There is no thermochronological evidence to indicate that the south-central part of Tibetan Plateau was influenced by the underthrusting of Indian Plate. The three-stage cooling history and the stages of tectonic exhumation were controlled completely by the closure of the Bangong–Nujiang Suture Zone along its eastern segment during Middle–Late Jurassic (165–150 Ma) and its western segment in the Early–Late Cretaceous (130–110 Ma), as well as by the collision between the Indian and Asian plates in the Paleogene (45–35 Ma).

Conflicting (U–Th)/He and fission track ages in apatite: Enhanced He retention, not anomalous annealing behaviour

While initial studies showed a high degree of consistency between AFTA and apatite (U–Th)/He dating, an increasing number of studies are reporting apatite (U–Th)/He ages which are older than expected on the basis of apatite fission track data from the same region. We present data from a range of geological settings to document a systematic discrepancy between the two systems, which becomes more pronounced in samples with older fission track ages (except for samples with very low uranium contents). Results from a granite pebble and enclosing volcanogenic sandstone provide a well-controlled test case in which independent constraints are available on the underlying thermal history. These demonstrate that the progressive discrepancy between the two techniques arises not from anomalous fission track annealing behaviour, as has been suggested, but as a result of a change in the He retention properties of apatite. This change appears to be linked to the degree of accumulated radiation damage within the crystal lattice, although underlying mechanisms remain unclear. We suggest detailed experiments should be performed to delineate and quantify the processes responsible. Until this is achieved, we suggest that apatite (U–Th)/He studies should also incorporate apatite fission track data, as well as other low temperature indicators, in order to monitor the (U–Th)/He system response and to guard against the anomalous behaviour described here.

A thermomechanical wedge model of Taiwan constrained by fission-track thermochronometry

We present 31 new apatite fission-track (AFT) ages for the island of Taiwan that, when combined with existing AFT and zircon fission-track (ZFT) data, provide regional spatial coverage of the island with respect to low-temperature thermochronometry. The overall pattern of ZFT and AFT ages in Taiwan exhibits unreset ages in the southern and western portions of the island and reset ages predominantly in the Central Range and eastern Taiwan. This pattern supports interpretations of the orogen kinematics as reflecting a crustal scale wedge with a southward propagating collision zone. In this model, new material is accreted to the wedge from the west and is transferred to the east with the greatest exhumation occurring along the eastern margin as recorded in the reset ages in the east and unreset ages in the west. The southward propagating collision is consistent with reset ages in the north, where erosional exhumation has been ongoing for longer, and unreset ages in the south, where the younger collision implies less time for erosional exhumation. Despite the variation in the age of the collision along the strike of the island, the widths of the AFT and ZFT reset age zones remain nearly constant between 23° 00′N to ∼ 24° 00′N and 23° 20′N to ∼ 24° 00′N, respectively, suggesting that the orogen is in an exhumational steady state over these regions with respect to the AFT and ZFT thermochronometers. We use the fission-track data in conjunction with observations of crustal structure, crustal fabric, and heat flow measurements to constrain a time-dependent, two-dimensional, thermomechanical model of orogen evolution. By accounting for the heat transfer, tectonic and erosion processes needed to predict AFT and ZFT ages, we are able to investigate the relationship between the measured ages and the tectonic characteristics of the orogen. With our model we conclude that: (1) roughly half of the material accretion in Taiwan occurs through underplating over an approximately 40 km wide region, (2) current average erosion rates are ∼ 3.3 mm/yr in the eastern Central Range and ∼ 2.3 mm/yr over the whole island, (3) the collision has been propagating southward at a rate between 20 and 51 km/Ma over the past 2–3 Ma, and (4) central Taiwan is in a topographic, thermal and exhumational steady state.