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New and under review...

Cheung, C.,  McKenzie, N. R., Savage, P., Beaty, B.,  Bauer, K., Colleps, C. L., Asael, D.,  Crowe, C., and Planavsky, N, Evaluating bedrock and seasonal influences on silicate weathering processes in Hong Kong rivers (In Review: Geochimica et Cosmochimica Acta)

Liu, H., Garber, J., Smye, A. J., Stockli, D. F, Colleps, C. L., Stockli, L. D., Wei, C., Cole, D., Planavsky, N. J., and McKenzie, N. R., Statistical assessment of zircon trace elements tracks tectonic regime changes and continental crust evolution for ~4.4 billion years (In Review: Nature Communications)

Commit to submit...

Nordsvan, A. R., Mitchell, R., Bauer, K., Colleps, C. L., McKenzie, N. R., Did Snowball Earth cause millions of years of terrigenous starvation? (Intended to submit to EPSL)

Adeoti, B, A., Webb, A. A. G., Genge, M. C., Huang, Y, King, G. E., Herman, F., Bouscary C., Gemignani, L., McKenzie, N., Colleps, C. L., OSL thermochronology reveals extremely rapid exhumation along the Sutlej River valley, NW Indian Himalaya initiated by the late Pleistocene-Early Holocene climate shift (Intended to submit to Geology)

Out and about...

Improving the efficiency of proton irradiations for 4He/3He Thermochronology:

Colleps, C. L., van der Beek, P., Amalberi, J., Denker, A., Tremblay, M. M., Bernard, M., Dittwald, A., and Bundesmann, J.
2024 Geochemistry, Geophysics, Geosystems


Synthesizing uniform and high concentrations of 3He within minerals via high-energy proton irradiation is paramount for 4He/3He thermochronology and helium diffusion kinetic studies. Proton irradiations of geological material have hitherto exclusively been routinely conducted at the Francis H. Burr Proton Therapy Center (FHB); we thus explored alternative irradiation protocols at two European-based facilities with the intention to improve the accessibility and efficiency in obtaining 4He/3He data. We conducted a single irradiation at the Paul Scherrer Institute (PSI) using an approach most similar to that used at FHB (wide, high-energy beam), and four irradiations at the Helmholtz Zentrum Berlin (HZB) using a newly developed in-vacuum irradiation protocol in a narrow, lower-energy but high-intensity beam. Internal shards of Durango apatite were irradiated in all experiments; 4He/3He release spectra and bulk 3He concentrations of PSI and HZB-irradiated Durango shards were compared to those from FHB to assess the quality of each experiment in terms of the quantity and uniformity of synthesized 3He. While 3He was uniformly synthesized in PSI-irradiated Durango shards, the bulk 3He concentration was below the required threshold due to limitations on the maximum allotted proton flux. Over the course of four irradiation experiments at HZB, the protocol evolved to ensure that uniform and high concentrations of 3He can be consistently induced. Furthermore, we demonstrate how HZB irradiations can be replicated using computer simulations, permitting the use of simulations to inform future modifications of the irradiation protocol in order to optimize the uniformity of the 3He distribution across all irradiated samples.

Magma-assisted Continental Rifting: The Broadly Rifted Zone in SW Ethiopia, East Africa

Erbello, A., Colleps, C. L., Melnick, D., Sobel, E., Bookhagen, B., Pingel, H., Zeilinger, G., van der Beek, P., and Strecker, M. R.,
2024 Tectonics


The Gofa Province and Chew Bahir Basin in the Broadly Rifted Zone (BRZ) between the southern Main Ethiopian Rift (sMER) and the northern Kenya Rift (nKR) record early volcanism and associated faulting in East Africa; however, the spatiotemporal relationships between volcanism and faulting remain poorly constrained. We applied apatite (U-Th)/He (AHe) and zircon (U-Th)/He (ZHe) thermochronometry to Neoproterozoic basement rocks from exhumed footwall blocks of the extensional Gofa Province and Chew Bahir Basin, and analyzed our result in the context of well-dated regional volcanic units in the BRZ to unravel the interplay between tectonic exhumation, faulting and volcanism. Single-grain AHe ages ranging from 1.0 to 136.8 Ma were recorded in 32 samples, and single-grain ZHe ages from three samples range between 142.2 and 335.6 Ma. The youngest AHe ages were obtained from the Chew Bahir Basin and the narrow deformation zone in the Gofa Province. Our thermal modeling results reflect little or no significant regional crustal cooling prior to extensive volcanism, which started at about 45 Ma. Conversely, new and previously published thermal history models suggest that widespread crustal cooling related to regional extension occurred between ∼27 and 20 Ma. Thermal modeling results from subsets of samples indicate that following this initial diffuse extensional deformation, renewed exhumation occurred along a narrow zone within the Gofa Province and the Chew Bahir Basin during the middle to late Miocene (15-6 Ma) and Pliocene (<5 Ma), respectively. The crustal cooling phases follow a regional trend in volcanic episodes. For example, initial cooling between 27 and 20 Ma corresponds with the end of widespread flood-basalt volcanism (45–28 Ma), suggesting that spatially diffuse normal faulting may have initiated shortly after the emplacement of voluminous and areally extensive flood basalts. The Miocene and Pliocene shifts in deformation along the Mali-Dancha and Bala-Kela basins in the Gofa Province and the Chew Bahir Basin, respectively, may indicate strain localization during the late stage of rifting and ongoing tectonic interaction between the sMER and the nKR. Our results support the notion of crustal weakening by massive volcanism as a precursor to widespread extensional faulting, and thus offer further insights into magma-assisted deformation processes in the East African Rift System.

Multivariant analysis of the sediment starved southeast Australian continental shelf

Nordsvan, A. R., McKenzie, N. R., Colleps, C. L., Koch, A., and Khan, N. S.
2023 Geological Society of America Bulletin


Continental shelves are the most morphologically variable element within the source-to-sink system owing to the numerous processes that influence their formation. A recent multivariate analysis of a global compilation of modern continental shelf data showed that much of the variability is related to tectonic setting, the degree to which the shelf has been glaciated, and carbonate production. While these factors play first-order roles in determining the morphology of shelves, other controlling mechanisms such as siliciclastic sediment supply, wave and tidal energy, bedrock lithology, and sea-level fluctuations are not as well understood. Here, we report findings from a detailed investigation of the southeast Australian shelf that explored how sediment distribution, wave energy, and bedrock lithology influence shelf morphology. The high-resolution analysis suggests that the southeast Australian shelf has 11 distinct shelf types. No strong relationships exist between the shelf attributes or shelf type with their onshore catchments. However, a substantial section boundary correlates with a bedrock contact between the Sydney Basin in the south and the New England Orogen to the north. South of this boundary, we propose that the shelf morphology reflects transgression with low sediment supply, whereas to the north, the morphology reflects transgression with higher sediment input. Although several factors contributed to this difference in shelf morphology, we suggest that sediment distribution and retention due to the active wave climate during the most recent transgression likely played a vital role.

Assessing the long-term low-temperature thermal evolution of the central Indian Bundelkhand craton with a complex apatite and zircon (U-Th)/He dataset

Colleps, C.L., McKenzie, N.R., van der Beek, P., Guenthner, W.R., Sharma, M., Nordsvan, A.R., Stockli, D.F.
2022 American Journal of Science


Modern approaches in low-temperature thermochronometry are capable of extracting long-term thermal histories from cratonic settings that may elucidate potential drivers of deep-time phases of intracontinental burial and erosion. Here, we assess the utilization of the Radiation Damage Accumulation and Annealing Model for apatite (RDAAM) and zircon (ZRDAAM) to track the long-term low-temperature thermal evolution of the Archean Bundelkhand craton and the surrounding undeformed strata of the ~1.7–0.9 Ga Vindhyan successions in central India. We correspondingly interpret a complex basement and detrital zircon and apatite (U-Th)/He (ZHe and AHe, respectively) dataset in light of observed model limitations and known geologic context. ZHe and AHe dates from across the craton reveal a significant (>300 Myr) date inversion between the two systems within grains with moderate to high effective uranium (eU) concentrations. Inverse thermal models utilizing current ZRDAAM and RDAAM parameters are not capable of reproducing observed coupled basement ZHe and AHe data for the same thermal history. However, meaningful thermal information can be extracted from AHe inverse models coupled with a forward modelling approach applied to detrital ZHe data from Vindhyan deposits, which have notably lower eU concentrations and yield significantly older ZHe dates (between ~1,475–575 Ma) than basement zircon. Resulting thermal models indicate that the Bundelkhand craton experienced peak burial temperatures of ~150°C between 850–475 Ma, followed by a major crustal cooling event at ~350–310 Ma, possibly driven by late Paleozoic glaciations and/or epeirorogenic uplift. Inverse models including AHe data require a Deccan Traps related thermal perturbation between ~66–65 Ma, and we suspect that this event overprinted basement zircon with moderate to high eU concentrations. Although the effects of zonation, grain morphology, and/or uncertainties in damage-annealing parameters contribute to disparities between predicted and observed AHe and ZHe dates, these factors alone cannot account for the major ZHe and AHe date inversion observed from the Bundelkhand craton. Instead, it is likely the case that current damage-dependent models for 4He diffusion are not adequately calibrated at the resolution necessary to predict short-lived thermal perturbations that occurred in a late phase relative to a prolonged period of extensive damage accumulation.

Zircon isotope–trace element compositions track Paleozoic–Mesozoic slab dynamics and terrane accretion in Southeast Asia

Liu, H., McKenzie, N.R., Colleps, C.L., Chen, W., Ying, Y., Stockli, L., Sardsud, A., Stockli, D.F.
2022 Earth and Planetary Science Letters


Variation in zircon trace element (TE) and isotopic composition data have been used to infer changes in global-scale processes; however, few studies have explored zircon TE data as a comprehensive means to track regional shifts in tectonic regimes. In this contribution, we explore the utility of zircon TE data to record the well-documented Late Paleozoic–Mesozoic tectonic history in Southeast Asia, which includes transitions from continental magmatism to island-arc extension, subsequent compression and island-arc accretion, and finally continental collision. We present new U-Pb ages, along with Lu-Hf isotopic and TE data, from 2,478 detrital zircon grains extracted from 17 modern river sediment samples collected across two major suture zones in Thailand. Our results show that zircon Th/U and Nb/Ta mean values increase after , whereas the percentage of classified ‘felsic’ zircon decline corresponding with the initiation of Nan back-arc basin extension and isolation of the Sukhothai Arc from Indochina. From ∼255 to 235 Ma, zircon εHf(t), LREE/HREE, (Eu/Eu*)N, (Ce/Ce*)N, Nb/Ta, and Th/U mean values decline, whereas Dy/Yb, U/Yb, and the proportion of classified S-type and ‘felsic’ zircon increase, showing the transition from I-type to S-type, and from more juvenile to more evolved magmatism. This transition reflects a shift from arc extension to compression via the closure of the Nan back-arc basin and the collision of the Sukhothai Arc with western Indochina, and the subsequent collision of Sibumasu with the Sukhothai Arc demarking the regional closure of the Paleo-Tethys ocean. Our data also show linear correlations between εHf(t)-DM and trace elemental data, particularly (Eu/Eu*)N, that reflect increasing sediment contamination within the melts. Lastly, our data illustrate that the Sibumasu–Sukhothai Arc collided ∼20 million years earlier in Thailand than in the Malay Peninsula, demonstrating along-strike diachroneity in Paleo-Tethys closure. Thus, time-integrated detrital zircon TE data may reliably track subduction slab dynamics and tectonic evolution beyond U-Pb and Hf isotope data alone.

Apatite (U-Th)/He thermochronometric constraints on the northern extent of the Deccan large igneous province

Colleps, C.L., McKenzie, N.R., Guenthner, W. R., Sharma, M., Gibson, T.M., Stockli, D.F.
2021 Earth and Planetary Science Letters


The volcanic emplacement and subsequent weathering of the Deccan Traps of India is believed to have had a significant influence in driving global climatic shifts from the Late Cretaceous and through the Cenozoic. The magnitude of the Deccan Traps’ impact on Earth’s surface environment is largely dependent on the speculated original footprint of the large igneous province. To test established estimates for the pre-erosive northern extent of the Deccan Traps, we applied low-temperature apatite (U-Th)/He thermochronology (AHe) on rocks from the Bundelkhand craton and overlying Proterozoic Vindhyan successions of central India ~150–200 km northeast of the northernmost preservation of Deccan basalts. New AHe data reveal young ~5–85 Ma AHe dates with low effective uranium concentrations (eU) between 5–22 ppm, with a steep positive date-eU correlation that plateaus at ~350 Ma in grains with eU values >50 ppm. Inverse thermal history modeling—utilizing AHe diffusion parameters of the Radiation Damage Accumulation and Annealing Model (RDAAM)—indicate that observed AHe date-eU correlations are most consistent with thermal histories that require the craton and Vindhyan strata to be at or near surface temperatures by ~66 Ma, followed by a discrete reheating event associated with Deccan volcanism. These results establish new minimal areal constraints for the northern extent of Deccan volcanism which thermally perturbed much of the Vindhyan succession. Thermal alteration of organic rich Vindhyan sediment may have provided an additional source of volatile emissions that facilitated late Maastrichtian warming at the onset of Deccan volcanism. New minimal northern constraints on Deccan volcanism additionally confirm that large volumes of Deccan basalts have been stripped away since the time of their emplacement, which poses considerable implications for unraveling their role in Cenozoic cooling.

Zircon and apatite U-Pb age constraints from the Bundelkhand craton and Proterozoic strata of central India: Insights into craton stabilization and subsequent basin evolution

Colleps, C.L., McKenzie, N.R., Sharma, M., Liu, H., Gibson, T.M., Chen, W., Stockli, D.F.
2021 Precambrian Research


The geologic processes involved in attaining strengthened cratonic lithosphere remain debated despite their importance for stabilization and long-term preservation. In central India, stabilization of the Bundelkhand craton has conventionally been attributed to the youngest magmatic event impacting the craton at ~2.5 Ga, though the post-amalgamation evolution of the craton prior to Proterozoic basin development is poorly understood. This study presents new basement zircon and apatite U-Pb age data along with new detrital zircon U-Pb age data from Proterozoic marginal sedimentary basin deposits to explore the post-magmatic and burial evolution of the Bundelkhand craton. Apatite from ~3.4–2.5 Ga granitoids and gneisses collected across the ~250 km wide craton yielded near uniform U-Pb ages between ~2.4–2.3 Ga, indicating broad-scale exhumation of the Bundelkhand craton through mid-crustal depths following amalgamation and felsic magmatism. Unroofing of the Bundelkhand craton at this time is corroborated by ~2.7–2.5 Ga detrital zircon U-Pb age peaks from basal sandstones of the Bijawar and Gwalior groups, which lie in direct nonconformable contact with the craton along both its southeastern and northwestern margins, respectively. These age populations reveal an abundance of zircon sourced directly from the Bundelkhand craton, and a sub-population of ~2.2–2.3 Ga grains provide a maximum depositional age for the oldest strata deposited on the craton. We speculate that the redistribution of heat producing elements associated with shallow emplacement of Bundelkhand granitoids and subsequent erosion may have enhanced lithospheric strengthening and facilitated a long-term thermal regime that promoted craton stability by ~2.2 Ga. Following stabilization, far-field marginal tectonism likely influenced the vertical motions within the Bundelkhand craton, inducing stages of broad subsidence and erosion recorded within the strata of the Lower and Upper Vindhyan successions.

Detrital zircon record of Phanerozoic magmatism in the southern Central Andes

Capaldi, T.N., McKenzie, N.R., Horton, B.K., Mackaman-Lofland, C, Colleps, C.L., Stockli, D.F.
2021 Geosphere


The spatial and temporal distribution of arc magmatism and associated isotopic variations provide insights into the Phanerozoic history of the western margin of South America during major shifts in Andean and pre-Andean plate interactions. We integrated detrital zircon U-Th-Pb and Hf isotopic results across continental magmatic arc systems of Chile and western Argentina (28°S–33°S) with igneous bedrock geochronologic and zircon Hf isotope results to define isotopic signatures linked to changes in continental margin processes. Key tectonic phases included: Paleozoic terrane accretion and Carboniferous subduction initiation during Gondwanide orogenesis, Permian–Triassic extensional collapse, Jurassic–Paleogene continental arc magmatism, and Neogene flat slab subduction during Andean shortening. The ~550 m.y. record of magmatic activity records spatial trends in magma composition associated with terrane boundaries. East of 69°W, radiogenic isotopic signatures indicate reworked continental lithosphere with enriched (evolved) εHf values and low (<0.65) zircon Th/U ratios during phases of early Paleozoic and Miocene shortening and lithospheric thickening. In contrast, the magmatic record west of 69°W displays depleted (juvenile) εHf values and high (>0.7) zircon Th/U values consistent with increased asthenospheric contributions during lithospheric thinning. Spatial constraints on Mesozoic to Cenozoic arc width provide a rough approximation of relative subduction angle, such that an increase in arc width reflects shallower slab dip. Comparisons among slab dip calculations with time-averaged εHf and Th/U zircon results exhibit a clear trend of decreasing (enriched) magma compositions with increasing arc width and decreasing slab dip. Collectively, these data sets demonstrate the influence of subduction angle on the position of upper-plate magmatism (including inboard arc advance and outboard arc retreat), changes in isotopic signatures, and overall composition of crustal and mantle material along the western edge of South America.

Sediment provenance of pre- and post-collisional Cretaceous–Paleogene strata from the frontal Himalaya of northwest India

Colleps, C.L., McKenzie, N.R., Horton, B.K., Webb, A.A.G., Ng, Y.W., Singh, B.P.
2020 Earth and Planetary Science Letters


Whereas the timing for India–Asia collision remains debated, contrasting collisional models provide testable predictions in terms of sediment source contributions during the accumulation of Paleocene to middle Eocene deposits now exposed in the frontal Himalayan system. Within the Lesser Himalaya and frontal thrust system of northwest India, discontinuous exposures of the Cretaceous Singtali Formation and upper Paleocene–middle Eocene Subathu Formation yield a record of these early collisional stages. To test competing collisional models, we analyze the provenance of these deposits with new detrital zircon U-Pb and Hf isotopic data which can distinguish among Indian plate, Asian plate, Kohistan-Ladahk arc, and various Himalayan sources. Detrital zircon age distributions for the Singtali Formation are dominated by Paleoproterozoic zircons with a distinct Cretaceous age component, whereas age data from the Subathu Formation record (1) a marked increase in the relative abundance of Cambrian–Neoproterozoic grains, (2) a decrease in the proportion of Paleoproterozoic grains, and (3) distinct Permian and Late Cretaceous–Paleocene age components. All Cretaceous grains from the Singtali Formation yielded crustal Hf isotopic signatures, indicating a distinctive pre-collisional source of Cretaceous grains of Indian affinity. Zircon Hf isotopic signatures from <320 Ma grains in the Subathu Formation show a significant lower to middle Eocene increase in source diversity, including juvenile grains most likely originating from the Asian plate and Kohistan-Ladakh arc. This requires inception of India-Asia collision by ∼44–50 Ma—the depositional age of the uppermost Subathu Formation. This major provenance shift is similar to that observed for pre- and post-collisional Tethyan Himalayan strata in the north, which is suggestive of a single contiguous basin linking the Lesser Himalaya by ∼44–50 Ma and contests the notion that the Lesser and Tethyan Himalaya were separated by a “Greater India Basin” during the Eocene. When coupled with the well documented Paleocene–early Eocene provenance record of the Tethyan Himalaya, these new data provide support for a collisional model in which Asian detritus reached the northernmost edge of India by ∼59 Ma with terminal closure of both the Shyok and Indus-Yarlung suture zones by ∼54 Ma.

Neogene Kinematic Evolution and Exhumation of the NW India Himalaya: Zircon Geo‐ and Thermochronometric Insights From the Fold‐Thrust Belt and Foreland Basin

Colleps, C.L., Stockli, D.F., McKenzie, N.R., Webb, A.A.G., Horton, B.K.
2019 Tectonics


The kinematic and exhumational evolution of the Lesser Himalaya (LH) remains a topic of debate. In NW India, the stratigraphically diverse LH is separated into the inner LH (iLH) of late Paleo‐Mesoproterozoic rocks and the outer LH (oLH) of Cryogenian to Cambrian rocks. Contradictory models regarding the age and structural affinity of the Tons thrust—a prominent structure bounding the oLH and iLH—are grounded in conflicting positions of the oLH prior to Himalayan orogenesis. This study presents new zircon (U‐Th)/He and U‐Pb ages from the thrust belt and foreland basin of NW India that refine the kinematic and exhumational evolution of the LH. Combined cooling ages and foreland provenance data support emplacement and unroofing of the oLH via southward in‐sequence propagation of the Tons thrust by middle Miocene time. This requires that, before India–Asia collision, the oLH was positioned as the southernmost succession of Neoproterozoic–Cambrian strata along the north Indian margin. This is further supported by detrital zircon U‐Pb ages from Cretaceous–Paleogene strata (Singtali Formation) unconformably overlying the oLH, which yield diagnostic Cretaceous detrital zircons correlative with coeval strata in the frontal Himalaya of Nepal. A pulse of rapid exhumation along the Tons thrust front at ~16 Ma was followed by east‐to‐west development of a midcrustal ramp at ~12 Ma which facilitated diachronous iLH duplexing. This duplexing shifted the locus of maximum exhumation northward, eroding away Main Central Thrust hanging wall rocks until the iLH breached the surface at ~9–11 Ma near Nepal and by ~3–7 Ma within the Kullu‐Rampur window.

Zircon (U‐Th)/He Thermochronometric Constraints on Himalayan Thrust Belt Exhumation, Bedrock Weathering, and Cenozoic Seawater Chemistry

Colleps, C.L., McKenzie, N.R., Stockli, D.F., Hughes, N.C., Singh, B.P.,  Webb, A.A.G., Myrow, P.M., Planavsky, N.J., Horton, B.K.
2018 Geochemistry, Geophysics, Geosystems


Shifts in global seawater 187Os/188Os and 87Sr/86Sr are often utilized as proxies to track global weathering processes responsible for CO2 fluctuations in Earth history, particularly climatic cooling during the Cenozoic. It has been proposed, however, that these isotopic records instead reflect the weathering of chemically distinctive Himalayan lithologies exposed at the surface. We present new zircon (U‐Th)/He thermochronometric and detrital zircon U‐Pb geochronologic evidence from the Himalaya of northwest India to explore these contrasting interpretations concerning the driving mechanisms responsible for these seawater records. Our data demonstrate in‐sequence southward thrust propagation with rapid exhumation of Lesser Himalayan strata enriched in labile 187Os and relatively less in radiogenic 87Sr at ∼16 Ma, which directly corresponds with coeval shifts in seawater 187Os/188Os and 87Sr/86Sr. Results presented here provide substantial evidence that the onset of exhumation of 187Os‐enriched Lesser Himalayan strata could have significantly impacted the marine 187Os/188Os record at 16 Ma. These results support the hypothesis that regional weathering of isotopically unique source rocks can drive seawater records independently from shifts in global‐scale weathering rates, hindering the utility of these records as reliable proxies to track global weathering processes and climate in deep geologic time.

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