Rapid exhumation since at least 13 Ma in the Himalaya recorded by detrital apatite fission-track dating of Bengal fan (IODP Expedition 354) and modern Himalayan river sediments

Ongoing exhumation of the Taiwan orogenic wedge revealed by detrital apatite thermochronology: The impact of effective mineral fertility and zero-track grains

“…The importance of U-rich zero-track grains to understand Taiwan erosion is highlighted by a comparison of detrital AFT data provided in this study with detrital AFT data recently published for the Bengal Fan (Huyghe et al 2020 Kirstein et al (2010). Zero-track grains thus provide firstorder constraints to Taiwan exhumation that must be duly considered for a correct geologic interpretation.…”

“…Bengal As suggested by Malusà and Fitzgerald (2020), this may be ascribed either to a fertility bias or to the underestimation of zero-track grains during analysis and subsequent data interpretation. Figure 9B shows, on the left, the mid-Bengal Fan lag-time diagram based on AFT central ages as proposed by Huyghe et al (2020). These authors have excluded part of the central ages from lag-time interpretation (in grey in Fig.…”

“…For example, low-grade metamorphic rocks are expected to shed many apatite grains with low [U] because of cogenetic epidote/allanite and/or monazite growth (Harlov 2015;O'Sullivan et al 2020). Apatite grains in Bengal Fan sediments (Huyghe et al 2020) yield ratios of U-rich zero-track grains vs. grains with fission tracks around ~1/3 (Fig. 1C).…”

“…The lesson learnt from detrital AFT analysis of Taiwan sediments can be applied to the interpretation of Bengal Fan AFT data recently published by Huyghe et al (2020). Bengal As suggested by Malusà and Fitzgerald (2020), this may be ascribed either to a fertility bias or to the underestimation of zero-track grains during analysis and subsequent data interpretation.…”

“…A recent detrital AFT data set for the Bengal Fan (Huyghe et al 2020), fed from the rapidly exhuming Namche Barwa syntaxis and from other regions of the central-eastern Himalaya eroded at slower rates (e.g., Garzanti 2019), includes many zero-track grains possibly derived from a rapidly exhuming syntaxial source (e.g., Najman et al 2019). However, information provided by zero-track grains was partly dismissed, and that signal was not detected by Huyghe et al (2020). An approach to overcome these problems based on recommendations by Galbraith (2005) is illustrated in this article using the Taiwan orogen as a test case.…”