We conducted petrographic, geochemical, and new U–Pb laser ablation inductively coupled mass spectrometry analyses of detrital zircons in the sandstone samples from the important Mengqiguer sandstone-type uranium deposit located in the Yili basin of the Xishanyao Formation. This formation (Shuixigou Group) is a major uranium-bearing target stratum in the basin. The main purpose of our investigations was to determine the provenance of the host sand units that has remained unclear to date. Our petrographic results suggested that the host sandstone is texturally and chemically immature, indicating superior physicochemical conditions for later uranium mineralisation. The major and trace element data of the detrital sandstone samples point towards the upper continental crust, and the chondrite-normalised rare earth element (REE) plots show enriched light REE and relatively flat heavy-REE distribution, with a negative Eu anomaly. The characteristics of the REEs and the trace elements point to felsic rocks as the provenance of the target strata with a continental arc tectonic setting. The detrital zircons indicate an age span of ∼235–∼2327 Ma, with major age populations of ∼300–∼500 Ma. The increasing amount of zircon grains from the Late Devonian to the Early Carboniferous coinciding with the age of volcanic magmatic activities of the Wusun and Nalati mountains indicates that the rocks formed under the Tianshan collisional orogeny and the subsequent extensional environment.

Taunsa uranium occurrence like other uranium resources in Pakistan is hosted by the Late Miocene-Pliocene age Litra Formation of the Siwalik Group molasse sediments. Taunsa uranium prospect is a unique phreatic-type uranium resource in terms of its disturbed geological setting of the eastern limb of the Zindapir anticline in the eastern Sulaiman range. Autoradiography technique was used to locate the spots of anomalous uranium concentration in thin sections from ore of Taunsa prospect. Twenty polished thin sections from uranium ore ranging from 200 ppm-600 ppm were attached to detectors for a month which produced prominent alpha track which were used to find the traps of uranium. Subsequently, these spots were studied under SEM and EPMA for further investigations of uranium phases. Autoradiography revealed that Taunsa uranium ore is mostly associated with organic matter (probably petroleum), black shale clasts, biotite, fougerite (a green colour rusty mineral) and with micritic clasts. This study suggests that prospective facies of the host sandstone containing relatively abundant black shale clasts, organic matter and biotite may be targeted during exploratory drilling in Taunsa uranium deposit and its extensions in the eastern limb of Zindapir anticline

Taunsa uranium occurrence like other uranium resources in Pakistan is hosted by the Late Miocene-Pliocene age Litra Formation of the Siwalik Group molasse sediments. Taunsa uranium prospect is a unique phreatic-type uranium resource in terms of its disturbed geological setting of the eastern limb of the Zindapir anticline in the eastern Sulaiman range. Autoradiography technique was used to locate the spots of anomalous uranium concentration in thin sections from ore of Taunsa prospect. Twenty polished thin sections from uranium ore ranging from 200 ppm-600 ppm were attached to detectors for a month which produced prominent alpha track which were used to find the traps of uranium. Subsequently, these spots were studied under SEM and EPMA for further investigations of uranium phases. Autoradiography revealed that Taunsa uranium ore is mostly associated with organic matter (probably petroleum), black shale clasts, biotite, fougerite (a green colour rusty mineral) and with micritic clasts. This study suggests that prospective facies of the host sandstone containing relatively abundant black shale clasts, organic matter and biotite may be targeted during exploratory drilling in Taunsa uranium deposit and its extensions in the eastern limb of Zindapir anticline

Copies of Supplementary Papers may be obtained from the Geological Society of Australia's website (www.gsa.org.au), the Australian Journal of Earth Sciences website (www.ajes.com.au) or from the National Library of Australia's Pandora archive (https://pandora.nla.gov.au/tep/150555).

A likely tuff bed lies along the gradational contact of the Middle and Upper Siwaliks in eastern Sulaiman Range, Taunsa area of Dera Ghazi Khan district, Pakistan. This tuffaceous unit is 0.5–3 m thick and extends for 10 km along the north-south strike in the eastern limb of the Zindapir anticline. It is greyish white to white on fresh surface, fine-grained to silty at the bottom and clayey at the top and thus shows a fining upward grain-size grading. The lower part of the ash bed shows a prominent lamination defined by megascopically visible abundant biotite, while the central and upper parts are so fine-grained that the individual minerals cannot be seen in hand sample. Unlike the lower well-laminated part, the central and upper parts are crudely laminated to apparently massive. The bulk samples analysed with X-ray diffraction consist of quartz, feldspar (plagioclase), biotite, clays, calcite and some ore mineral likely spinel, while the clay-size fractions contain illite, chlorite, biotite and probably their mixed-layered varieties. The colour, texture, presence of abundant biotite and stratigraphic position of the Taunsa tuff correlate with those reported from Potwar plateau and from Kashmir basin. However, the apparent absence of smectite from the XRD pattern makes the Taunsa ash bed different from both Potwar and Kashmir tuffs. The present stratigraphic position of the tuff bed corresponds to shallow diagenetic zone, while the absence of smectite in the tuff and crystallinity of illite suggest that the tuff is probably derived upon reworking from a deeper diagenetic zone belonging to a lower stratigraphic level. The Eocene or other older pre-Siwalik units in Pakistan may have or had some primary ashfall deposits as reported in the northwestern Himalayas of India. This older volcanic ash may have been reworked to its present site of occurrence along the gradational contact of the Middle and the Upper Siwaliks in Taunsa area of Dera Ghazi Khan. However, the primary source of the Taunsa tuff may belong more likely to Chagai arc in Pakistan than to Dacht-e-Nawar volcanic complex in Afghanistan.