Rocks and Water

Article on the South Lunggar rift, western Tibet, accepted in Tectonics

This was a post that originally appeared on my old blog

A big part of my PhD was the exploration of a large, but essentially unknown, active rift in southwest Tibet, the South Lunggar rift. We mapped the rift, and did a solid amount of zircon (U-Th)/He thermochronology, combined with thermal modeling using Pecube, and did some ancillary zircon U-Pb geochronology as well.

The rift itself is a central horst bound by two rift basins, with major, active normal faults between the horst and the rift. Structural and thermal observations and modeling suggest a total of 10-21 km extension since ~10-12 Ma, at modern rates of ~1-3 mm/yr. There is pretty good evidence for an rapid increase in extension rate at 8 Ma, on the most significant fault in the rift, the low-angle South Lunggar Detachment.

We have just gotten a paper accepted in Tectonics that covers most of what is known about the rift. The official Tectonics page is here, although the PDF that they host has some serious formatting errors and the figures are atrociously pixelated and distorted; this will be fixed in the future, I assume.
The ungated Word-style formatted PDF with correct figures is here, from my ResearchGate page. The paper itself is pretty big; 90 something manuscript pages; it’ll probably be 30+ pages once formatted.

The paper is pretty broad in scope, and represents quite a bit of work. As I mentioned above, the rift was basically unknown before we went there, though there was a M ~6.8 normal faulting event in late August 2008 that was studied by John Elliott (paper here) and in more detail by Isabelle Ryder (here). Both of these papers simply studied the earthquake itself, from remotely-collected geophysical data. Our study here represents about a month of mapping and sample collection over two campaigns, as well as ~35 new zircon (U-Th)/He cooling ages, 2 zircon U-Pb crystallization ages, and a ton of thermal modeling (~25,000 Pecube runs). The goal was to have one single, thorough paper that presents all of our observations, data, modeling, interpretations–almost like a treatise on the rift. It might have been wiser to break it down into several shorter papers, but that’s just not how it went…

In any case, it’s finally out. Enjoy!