Nanga Parbat Gneiss

Kazmi & Jan (1997), after Tahirkheli (1987–1992): the amphibolite-facies Nanga Parbat Gneisses are dated at 1,800–2,700 Ma — an older span (Paleoproterozoic–Neoarchean) than the curated 'Mesoproterozoic to Neoproterozoic'; flagged for reconciliation.

Kazmi, A.H. & Jan, M.Q. (1997)

Zeitler et al. (1989): U/Pb zircon dating gives protolith ages of ~1850 Ma for the Iskere Gneiss and 400–500 Ma for the structurally lower Shengus Gneiss (which may be a metamorphosed equivalent of the Mansehra Granite and other Paleozoic S-type Himalayan granites). Critically, thin high-U zircon rims on the Iskere Gneiss yield 2.3–11 Ma ages, showing that the high-grade metamorphism of the massif is TERTIARY, not Precambrian — the curated Precambrian age applies to the protolith, not the metamorphic fabric.

Zeitler, P.K., Sutter, J.F., Williams, I.S., Zartman, R. & Tahirkheli, R.A.K. (1989)

Kazmi & Jan (1997): the Nanga Parbat Gneisses form the >15 km-thick Proterozoic Nanga Parbat Group (Madin 1986) of the Nanga Parbat–Haramosh Massif (the Nanga Parbat Syntaxis, a re-entrant into the Kohistan arc), comprising the basal Shingus paragneiss, the Iskere orthogneiss, upper amphibolites and marbles, and the Haramosh Schist; the group is intruded by younger undeformed granites, pegmatites and mafic dykes. The Precambrian Salkhala Formation is thrust over the gneisses along the Shontargali Thrust (an MCT analogue), and the Liachar Thrust carries the high-grade gneisses onto Recent Indus-valley glacial sediments.

Kazmi, A.H. & Jan, M.Q. (1997)

Zeitler et al. (1989): the Nanga Parbat–Haramosh Massif — a north-pointing promontory of Indian-plate high-grade gneiss at the northwestern Himalayan syntaxis — reached peak metamorphic temperatures at 25–30 Ma. Its post-metamorphic cooling over the last 5–10 Ma has been controlled by the Raikhot Fault together with passive uplift beneath the overthrust Kohistan arc; net cooling rates for gneisses now at the Indus River accelerated from ~20 °C/Ma at ~20 Ma to ~300 °C/Ma at 0–0.4 Ma, recording extraordinarily rapid recent exhumation.

Zeitler, P.K., Sutter, J.F., Williams, I.S., Zartman, R. & Tahirkheli, R.A.K. (1989)

Madin et al. (1989): the western boundary of the Nanga Parbat–Haramosh Massif is not the Main Mantle Thrust but the younger, recently active dextral-reverse Raikot fault, which truncates the MMT and separates the Kohistan-arc rocks (Kohistan Sequence) from the high-grade Proterozoic metasediments (the 'Nanga Parbat Group') and orthogneisses of the Indian craton. The Raikot fault (mylonite zones plus discrete faults) accommodated ~15–25 km of late Cenozoic crustal uplift, appears to involve the Moho, and is interpreted as a terminal tear fault on the Main Central Thrust following a major — possibly pre-collision Indian-plate — crustal structure.

Madin, I.P., Lawrence, R.D. & Ur-Rehman, S. (1989)