College of Science and Engineering CSE publications Recent publications in Earth and Environmental Sciences

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Recent publications in Earth and Environmental Sciences

Rowe, Cassandra, David, Bruno, Mialanes, Jerome, Ulm, Sean, Petchey, Fiona, Aird, Samantha, McNiven, Ian J., Leavesley, Matthew, and Richards, Thomas (2020) A Holocene record of savanna vegetation dynamics in southern lowland Papua New Guinea. Vegetation History and Archaeobotany, 29 (1). pp. 1-14.
The southern lowlands of Papua New Guinea (PNG) are biogeographically distinct. Vast tracts of savanna vegetation occur there and yet most palaeoecological studies have focused on highlands and/or forest environments. Greater focus on long-term lowland environments provides a rare opportunity to understand and promote the significance of local and regional savannas, ultimately allowing non-forested and forested ecosystem dynamics to be compared. This paper examines palaeoecological and archaeological data from a lowland open savanna site situated on the south-central PNG coastline. The methods used incorporate pollen and micro-charcoal analyses, artefact recovery and sediment descriptions. We conclude with an environmental model of sedimentation and vegetation change for the past c. 5,800 years, revealing a mid to late Holocene savanna interchange between herbaceous and woody plant growth, with fluctuating fire occurrence increasing toward the present day. Increased silt deposition and modified regional hydrology are also recorded. Environmental changes correspond in timing with the start of permanent settlements and human use of fire. In particular, landscape burning for hunting and gardens for agriculture have helped create the open ecosystem still evident today.

Niu, Si-Da, Li, Sheng-Rong, Huizenga, Jan Marten, Santosh, M., Zhang, De-Hui, and Li, Zheng-Da (2020) ⁴⁰Ar/³⁹Ar geochronology, fluid inclusions, and ore‐grade distribution of the Jiawula Ag–Pb–Zn deposit, NE China: implications for deposit genesis and exploration. Geological Journal, 55 (2). pp. 1115-1127.
The Jiawula Ag–Pb–Zn deposit is located in the northern part of the Great Xing'an Range metallogenic belt within the eastern segment of the Central Asian Orogenic Belt. Here, we report results from muscovite ⁴⁰Ar/³⁹Ar geochronology and fluid inclusion study and formulate a vertical projection map of the ore grade in this deposit. The muscovite from the Jiawula deposit yields a plateau age of 133.27 ± 0.66 Ma and a ⁴⁰Ar/³⁹Ar isochron age of 131.88 ± 0.83 Ma. The muscovite ⁴⁰Ar/³⁹Ar data indicate a discrete second hydrothermal event postdating the mineralization, which we correlate with post‐collisional extension after the subduction direction of the Palaeo‐Pacific Plate changed. Low‐salinity aqueous fluid inclusions in quartz from the Jiawula deposit represent meteoric water or groundwater. Based on the fluid inclusion study, the fluids were trapped during cooling and decompression, which may have resulted in metal precipitation. We envisage that the copper precipitated from a high‐temperature fluid in the southern domain whereas lead, zinc, and silver precipitated at a lower temperature in the north. The spatial distribution of the ore‐forming elements, therefore, reflects the ore fluid migration‐cooling path from the south to north.

Chen, Fuchuan, Deng, Jun, Wang, Qingfei, Huizenga, Jan Marten, Li, Gongjian, and Gu, Youwei (2020) LA-ICP-MS trace element analysis of magnetite and pyrite from the Hetaoping Fe-Zn-Pb skarn deposit in Baoshan block, SW China: implications for ore-forming processes. Ore Geology Reviews, 117. 103309.
The Hetaoping deposit is one of the largest Fe-Zn-Pb skarn deposit in SW China, which is characterized by Zn-Pb mineralization in the upper part and the Fe mineralization in the deeper part. The Fe mineralization is dominated by magnetite and pyrite. Magnetite can be subdivided into four types: primary banded magnetite samples in clinopyroxene-actinolite skarn (Mt-1), primary disseminated magnetite in garnet skarn (Mt-2), primary disseminated magnetite in clinopyroxene-actinolite skarn (Mt-3), and altered magnetite in clinopyroxene-actinolite skarn (Mt-4). Pyrite can be subdivided into three types: pyrite in oxide-ore stage (Py-1), pyrite in early sulfide ore stage (Py-2), and pyrite in late sulfide-ore stage (Py-3). The flat time-resolved signals of laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) imply that trace elements exist mainly in the form of isomorphism in magnetite and pyrite with the exception some incompatible trace elements (e.g., Ca, K and Na in magnetite and Pb, Bi and Ag in pyrite). Trace element concentrations in magnetite and pyrite demonstrate that the ore-forming fluid in Hetaoping is of magmatic origin. Furthermore, compared to porphyry, IOCG, Kinuna and BIF type magnetite, the magnetite from Hetaoping has relatively low Ti, V and Ni concentrations but high Al, Mn and Ca concentrations, implying a typical skarn genesis. The variation of Ti concentrations in magnetite is an indication of the formation temperature and shows that banded magnetite (Mt-1) precipitated in a relatively high-temperature environment compared with disseminated magnetite (Mt-2 and Mt-3). Compared to Mt-1 and Mt-3, Mt-2 has a higher Si, Al, and W contents and a lower Mg and Mn contents. The Mn content increases from Py-1 to Py-2, and decreases from Py-2 to Py-3, suggesting that the fluid-rock interaction increased from the oxide-ore stage to the sulfide-ore stage, and decreased from sulfide-ore stage to post-ore stage. The variation of the V concentration in magnetite grains indicates a relatively higher oxygen fugacity of Mt-2 compared to Mt-1 and Mt-3, implying that the oxygen fugacity of the ore-forming fluid in the garnet skarn zone is higher than that in clinopyroxene-actinolite skarn zone. The variable oxygen fugacity probably caused spatial zoning of mineralization in Hetaoping Fe-Zn-Pb skarn deposit. The temperature and oxygen fugacity of the ore-forming fluid, and the extent of fluid-rock interaction, controlled the temporal order and spatial zonation of magnetite and sulfide precipitation, which led to the formation of the Hetaoping Fe-Zn-Pb skarn deposit.

Preston, Robyn, Gratani, Monica, Owens, Kimberley, Roche, Poornima, Zimanyi, Monika, and Malau-Aduli, Bunmi (2020) Exploring the impact of assessment on medical students’ learning. Assessment and Evaluation in Higher Education. (In Press)
What and how students learn depend largely on how they think they will be assessed. This study aimed to explore medical students’ perception of the value of assessment and feedback on their learning, and how this relates to their examination performance. A mixed methods research design was adopted in which a questionnaire was developed and administered to the students to gain their perceptions of assessments. Perceptions were further explored in focus group discussions. Survey findings were correlated with students’ performance data and academic coordinators’ perceptions. Students’ perceptions of the level of difficulty of different assessments mirrored their performance in examinations, with an improvement observed in clinical assessments as students progressed through their degree. Students recognised that feedback is important to allow improvements and seek more timely, better quality and personalised feedback. Academic coordinators identified that some of the students’ suggestions are more realistic than others. Students had a positive attitude towards assessment, but emphasised the need for educators to highlight the relevance of assessment to clinical practice.

Duce, Stephanie, Dechnik, Belinda, Webster, Jody M., Hua, Quan, Sadler, James, Webb, Gregory E., Nothdurft, Luke, Salas-Saavedra, Marcos, and Vila-Concejo, Ana (2020) Mechanisms of spur and groove development and implications for reef platform evolution. Quaternary Science Reviews, 231. 106155.
Contemporary understanding of Holocene coral reef development is based primarily on sub-surface investigations of reef flat, back reef and lagoon zones. Few studies of Holocene fore reef development exist, constituting a significant gap in our understanding of reef evolution. The spur and groove (SaG) zone is a distinct, understudied, feature of fore reefs worldwide. We review SaG development from previous studies and present 29 new SaG short cores with 52 ¹⁴C and U-Th ages from six fore reef regions of Heron and One Tree reefs, the first such data from the Great Barrier Reef. Remarkably, we found that SaGs do not necessarily accrete in the same direction as their adjacent reef flat. We identified three modes of reef flat and SaG lateral accretion: Mode 1 - lagoonward accretion of both the reef flat and SaGs; Mode 2 - lagoonward accretion of the reef flat but seaward accretion of the SaGs; Mode 3 - seaward accretion of both the reef flat and SaGs. Most SaG zones (five of the six studied) accreted in a seaward direction (Modes 2 or 3). Hydrodynamic conditions and local topography appear to be the dominant factors determining which mode occurs. Episodic high-energy events are also likely to play an important role in SaG formation. Our findings suggest that traditionally held models of reef evolution whereby lagoonal, mature reefs fill, developing into senile platform reefs, may not hold. Rather, reef flats may continue to expand seaward on their leeward, and semi-exposed fronts to increase in size while maintaining their lagoons.

Munksgaard, Niels C., Zwart, Costijn, Haig, Jordahna, Cernusak, Lucas A., and Bird, Michael I. (2020) Coupled rainfall and water vapour stable isotope time series reveal tropical atmospheric processes on multiple timescales. Hydrological Processes, 34 (1). pp. 111-124.
High-frequency stable isotope data are useful for validating atmospheric moisture circulation models and provide improved understanding of the mechanisms controlling isotopic compositions in tropical rainfall. Here, we present a near-continuous 6-month record of O- and H-isotope compositions in both water vapour and daily rainfall from Northeast Australia measured by laser spectroscopy. The data set spans both wet and dry seasons to help address a significant data and knowledge gap in the southern hemisphere tropics. We interpret the isotopic records for water vapour and rainfall in the context of contemporaneous meteorological observations. Surface air moisture provided near-continuous tracking of the links between isotopic variations and meteorological events on local to regional spatial scales. Power spectrum analysis of the isotopic variation showed a range of significant periodicities, from hourly to monthly scales, and cross-wavelet analysis identified significant regions of common power for hourly averaged water vapour isotopic composition and relative humidity, wind direction, and solar radiation. Relative humidity had the greatest subdiurnal influence on isotopic composition. On longer timescales (weeks to months), isotope variability was strongly correlated with both wind direction and relative humidity. The high-frequency records showed diurnal isotopic variations in O- and H-isotope compositions due to local dew formation and, for deuterium excess, as a result of evapotranspiration. Several significant negative isotope anomalies on a daily scale were associated with the activity of regional mesoscale convective systems and the occurrence of two tropical cyclones. Calculated air parcel back trajectories identified the predominant moisture transport paths from the Southwest Pacific Ocean, whereas moisture transport from northerly directions occurred mainly during the wet season monsoonal airflow. Water vapour isotope compositions reflected the same meteorological events as recorded in rainfall isotopes but provided much more detailed and continuous information on atmospheric moisture cycling than the intermittent isotopic record provided by rainfall. Improved global coverage of stable isotope data for atmospheric water vapour is likely to improve simulations of future changes to climate drivers of the hydrological cycle.

Zhao, Xu, Wei, Junhao, Fu, Lebing, Huizenga, Jan Marten, Santosh, M., Chen, Jiajie, Wang, Dianzhong, and Li, Aobing (2020) Multi-stage crustal melting from Late Permian back-arc extension through Middle Triassic continental collision to Late Triassic post-collisional extension in the East Kunlun Orogen. Lithos, 360-361. 105446.
The East Kunlun Orogen is an important part of the East Tethys region and has received significant attention with regards to the evolution of the Tethys Ocean. This contribution presents geochronological,whole-rockmajor and trace element geochemical, and Sr-Nd-Hf isotopic data of magmatic rocks within the Kengdenongshe polymetallic deposit in the eastern part of the East Kunlun Orogen. Here, we report zircon U\\Pb ages of ca. 257 Ma and ca. 211 Ma for granite porphyry intrusions, and ca. 240Ma for the rhyolitic tuff. These rocks are characterized by high SiO₂, variable Al₂O₃ and K₂O, lowNa2O, MgO and CaO contents, and high A/CNK ratios,which is typical of S-type granitic rocks. They exhibit large-ion lithophile element enrichment, depletion of high field strength elements, have low (La/Yb)N ratios, and negative εNd anomalies. They also display variable (⁸⁷Sr/⁸⁶Sr)i ratios (0.709981 to 0.720907), negative εNd (t) values (−8.7 to −5.5), and a wide (enriched) zircon εHf (t) range (−10.1 to −0.8). The geochemical and isotope data indicate magma derivation through dehydration melting of heterogeneous crustal sources including clay-poor meta-sedimentary rocks and amphibolite, which are both parts of the East Kunlun Orogen basement. These results provide evidence for the evolution of the Paleo-Tethys Ocean in the East Kunlun Orogen including Late Permian (266–255 Ma) back-arc extension, Late Permian to Middle Triassic (255–240 Ma) subduction, Middle Triassic (240–225 Ma) continental collision, and Late Triassic (b 225 Ma) post-collisional extension. This study further suggests that the 257 Ma and 211 Ma granite porphyries are related to the asthenosphere upwelling in a back-arc basin and post-collision extensional setting, respectively. The 240 Ma rhyolitic tuff is linked to anatexis associated with crustal thickening during continental collision.

Knutsen, Espen M., and Oerlemans, Emma (2020) The last dicynodont? Re-assessing the taxonomic and temporal relationships of a contentious Australian fossil. Gondwana Research, 77. pp. 184-203.
Dicynodonts, a lineage of non-mammalian therapsids, who's derived taxa evolved edentulous beaked jaws sporting a pair of caniniform tusks, dominated the herbivorous terrestrial vertebrate fauna for much of the Permian and Triassic periods. Long assumed to have met their demise during the end-Triassic extinction event, the discovery of a fragmentary possible dicynodont in Cretaceous rocks in Queensland Australia, potentially extended the longevity of the lineage by nearly 100 million years. This study reassesses the geological, anatomical and historical aspects of this specimen through museum archival research, detrital zircon geochronology, trace element analysis and x-ray synchrotron microtomography, and present new knowledge regarding its temporal, geographical and biological origins, supporting a late Cenozoic (Pliocene-Pleistocene) mammalian megafaunal affinity for the specimen, resulting in a lack of evidence for post-Triassic survival of dicynodonts.

Dai, Zuo-Wen, Huang, Han-Xiao, Li, Guang-Ming, Huizenga, Jan-Marten, Santosh, M., Cao, Hua-Wen, Huang, Chun-Mei, and Ding, Jun (2020) Formation of Late Cretaceous high-Mg granitoid porphyry in central Lhasa, Tibet: implications for crustal thickening prior to India-Asia collision. Geological Journal. (In Press)
The Tibetan Plateau is characterized by the largest crustal thickness on Earth, although the timing of formation of the plateau remains debated. In this study, we present in situ laser ablation-inductively coupled plasma-mass spectrometry zircon U–Pb ages and Hf isotopes, and whole-rock geochemical data on porphyritic granitoids of Sebuta in the central Lhasa block. Our zircon U–Pb data indicate that these rocks emplaced at ca. 89 Ma, in the early Late Cretaceous. Geochemically, the Sebuta biotite granite porphyry can be broadly divided into two subtypes, namely metaluminous porphyry and peraluminous porphyry. The metaluminous porphyry has high SiO2, Al2O3, Sr, low Y and Yb contents, and high Sr/Y and LaN/YbN ratios, showing adakitic features. These rocks have high K2O and Th contents, low Ti/Eu and Nd/Sm ratios, indicative of a continental crust affinity. Positive zircon εHf(t) values, along with high Mg#, Cr and Ni, imply that the Sebuta adakitic porphyry was most likely derived from partial melting of a delaminated thickened juvenile lower crust, and that the initial melts interacted with mantle peridotite during ascent. The field features, petrographic characteristics, formation age, ore-bearing potential, and Hf isotope of the peraluminous porphyry are similar to those of the Sebuta adakitic porphyry, indicating that the peraluminous porphyry was likely formed by contamination with ancient crustal material and fractional crystallization from the same primary adakitic magmas which generated the Sebuta adakitic porphyry. Residual phases of amphibole + plagioclase + garnet + rutile in the source region, together with previous studies, suggest that the crust beneath the central northern Lhasa block experienced thickening during the early Late Cretaceous, and had already been thickened to more than 50 km by the Late Cretaceous (ca. 89 Ma).

Sheaves, Marcus, Abrantes, Katya, Barnett, Adam, Benham, Claudia, Dale, Patricia, Mattone, Carlo, Sheaves, Alison, Waltham, Nathan, and Bradley, Michael (2020) The consequences of paradigm change and poorly validated science: the example of the value of mangroves to fisheries. Fish and Fisheries. (In Press)
Accuracy in representing, communicating and reporting science is critical to the translation of science into knowledge. Any lack of accuracy degrades the quality and reliability of consequent decisions. One common cause of inaccuracy is the use of superseded paradigmatic concepts with a lack of careful validation. This leads to evidentiary dissonance (an apparent abundance of evidence with little basis in actual reported scientific findings). We illustrate the nature and consequences of evidentiary dissonance using the example of estimates of the value of mangroves to fisheries, which are key motivators of decision‐making around land‐use activities in mangroves systems, mangrove restoration and disturbance offset initiatives. Causes include the use of inappropriate or inaccurate data and inadequate support for reasoning used to develop estimates of fisheries value. Evidentiary dissonance in linking estimates to scientific understanding has produced a citable and cited body of work with tenuous foundations in current ecological understanding, and a body of literature that is likely to lead to unrealistic expectations, misdirected and wasted resources, and perverse management outcomes.

Wiersma, Jelle P., Roberts, Eric M., and Dirks, Paul H. G. M. (2020) Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin-bearing (Homo naledi) Rising Star Cave system, South Africa. Sedimentology, 67 (2). pp. 897-919.
Unconsolidated mud clast breccia facies in the hominin-bearing (Homo naledi) Rising Star Cave, Cradle of Humankind, South Africa, are interpreted to have formed through a process termed sedimentary autobrecciation in this study. This process, by which most of the angular mud clast breccia deposits are thought to have formed autochthonously to para-autochthonously via a combination of erosion, desiccation, diagenesis and microbial alteration of laminated mud deposits, is thought to have taken place under relatively dry (i.e. non-flooded) conditions inside the cave. Subsequently, gravitational slumping and collapse was the dominant mechanism that produced the mud clast breccia deposits, which commonly accumulate into debris aprons. The mud clast breccia is typically associated with (micro) mammal fossils and is a common facies throughout the cave system, occurring in lithified and unlithified form. This facies has not been described from other cave localities in the Cradle of Humankind. Additionally, sedimentary autobrecciation took place during the deposition of some of the fossils within the Rising Star Cave, including the abundant Homo naledi skeletal remains found in the Dinaledi Subsystem. Reworking of the mud clast breccia deposits occurs in some chambers as they slump towards floor drains, resulting in the repositioning of fossils embedded in the breccias as evidenced by cross-cutting manganese staining lines on some Homo naledi fossil remains. The formation of the unlithified mud clast breccia deposits is a slow process, with first order formation rates estimated to be ca 8 x 10(-4) mm year(-1). The slow formation of the unlithified mud clast breccia facies sediments and lack of laminated mud facies within these deposits, indicates that conditions in the Dinaledi Chamber were probably stable and dry for at least the last ca 300 ka, meaning that this study excludes Homo naledi being actively transported by fluvial mechanisms during the time their remains entered the cave.

Van Ryt, M.R., Sanislav, I.V., Dirks, P.H.G.M., and Huizenga, J. (2020) Trace element associations in magnetite and hydrothermal pyrite from the Geita Hill gold deposit, Tanzania. Journal of Geochemical Exploration, 209. 106418.
Gold mineralization in the Geita Hill deposit is associated with pyrite formed along microfracture networks and sulfidation fronts together with K-feldspar and biotite. The sulfidation fronts are best developed in magnetite-bearing ironstone. The gold is present mainly as electrum and gold tellurides along grain boundaries, and as inclusions in pyrite, quartz, biotite and K-feldspar. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of pyrite and magnetite grains reflect complex fluid-host rock interactions. Magnetite textures and chemistry change with alteration intensity, indicating the progression of the alteration front into the host rock. Pyrite textures are uniform across all rock types and reflect late-tectonic growth linked to multi-staged infiltration of hydrothermal fluids. Trace element distribution patterns in pyrite are locally complex and influenced by host rock chemistry. Gold distribution patterns in pyrite correlate closely with Te, Ag, Bi and Pb, indicating that gold occurs in micro- and nano-inclusions of telluride minerals. This is especially so for gold in quartz veins, whereas gold in ironstone and diorite also occurs as electrum with an average Au/Ag ratio of 0.41. As, Co and Ni in pyrite are lattice bound and occur in high concentrations in ironstone and diorite where they show characteristic growth zoning patterns. Pyrite in quartz veins has As, Co and Ni concentrations that are low and variable. Cr, Cu, Mo, Mn and Zn are present in all rock types in isolated inclusions in pyrite grains, whilst Pb, Bi and Sb occur in more dispersed patches of fine clustered inclusions. The Se content in pyrite is typical for Archean gold deposits, and reflects an average temperature of ~340 °C for the mineralizing fluid. The Co/Ni ratio of pyrite grains varies between 0 and 5.2 in ironstone and diorite, and most likely reflects the equilibration Co/Ni ratio of the host rock. The Co/Ni ratio of pyrite grains in quartz veins varies between 1 and 12, and is consistent with a magmatic-hydrothermal origin for the ore fluid. Trace element distribution patterns in magnetite and pyrite indicate that As, Ni, Co, Cr, Mn and Cu were mostly locally derived, and remobilised into the pyrite during sulfidation of the host rock. The concentrations of these elements are strongly lithologically controlled, and they are not consistently incorporated into the pyrite after initial stages of growth. Au, Ag, Te, Bi and Pb were externally derived, and closely correlate in all varieties of pyrite as well as strongly altered magnetite. The alteration footprint of the Geita Hill deposit is limited in extent, and does not involve As and Sb that are typically enriched in Archaean lode-gold systems. Instead, Te and Bi are most characteristic for the deposit and could be of use as path finder elements together with altered magnetite grains.

Puga-Bernabéu, Ángel, Webster, Jody Michael, Beaman, Robin Jordan, Thran, Amanda, López‐Cabrera, Javier, and Daniell, James (2020) Submarine landslides along the mixed siliciclastic-carbonate margin of the Great Barrier Reef (offshore Australia). In: Ogata, Kei, Festa, Andrea, and Pini, Gian Andrea, (eds.) Submarine Landslides: subaqueous mass transport deposits from outcrops to seismic profiles. Geophysical Monograph, 246 . Wiley, Washington, DC, USA, pp. 313-337.
Submarine landslides on modern mixed siliciclastic-carbonate margins are poorly understood compared to their counterparts in other settings. We present a synthesis of four representative submarine landslides types along the Great Barrier Reef margin, the largest extant mixed siliciclastic-carbonate province in the world. The investigated examples are 5–31 km in length, extend over 18–528 km2, and have remobilized an estimated 0.025–32 km3 of sediments. They display morphological features corresponding to debris avalanches and slides. The estimated timing of two dated landslides is coincident with deglaciations corresponding to the transitions MIS 12–11 and MIS 2–1. Large seismic events were the most likely triggering mechanism for the landslides, where high pore water pressure in examples close to paleo-deltaic systems could also have preconditioned the eventual failure. A potential preconditioning factor, yet to be confirmed, is the geologic control associated with alternating mixed siliciclastic and carbonate sediments in the failed lithologies. The Gloria Knolls Slide is large enough to have significant tsunamigenic potential. Tsunami simulations show that this landslide would produce a sizable tsunami under present-day sea level conditions, with coastal run-up heights of 0.5–2 m. We highlight a reef buffering effect due to broader-scale shelf bathymetry and the complex structure of coral reefs.

Liu, Guangxian, Yuan, Feng, Deng, Yufeng, Wang, Fangyue, White, Noel, Huizenga, Jan, Li, Yue, Li, Xiaohui, and Zhou, Taofa (2020) Ore-fluid geochemistry of the Hehuashan Pb–Zn deposit in the Tongling ore district, Anhui province, China: evidence from REE and C–H–O isotopes of calcite. Ore Geology Reviews, 117. 103279.
Calcite is the main gangue mineral of the Hehuashan lead–zinc deposit, which is located in the Tongling ore district, Anhui Province, East China. The ore bodies of the Hehuashan deposit are hosted by dissolution breccia of the Lower Triassic carbonate sediments. We report petrography, rare earth elements (REE), and C–H–O isotope data of four generations of calcite recognized in the Hehuashan deposit, namely the pre-ore stage calcite (Cal-1), early ore-forming stage calcite (Cal-2), late ore-forming stage calcite (Cal-3) and post-ore stage calcite (Cal-4). In addition, we also report C–H–O isotopes data of dolostone from the Lower Triassic carbonate sediments. All four calcite generations show a low ∑REE content (13–50 ppm on average), indicating that the related ore-forming fluids may not have been derived a magmatic fluid but rather be derived from the carbonate sediments or basinal brines. Low LREE/HREE ratio (1.1–6.1 on average) of all four calcite generations implies that no significant REE fractionation happened during the mineralizing processes. The wide distribution of Y/Ho ratios (17–70) of calcite indicates a result of fluids mixing. The δ¹³C values of calcite (1.4‰ to 4.2‰) are comparable to marine carbonates, but the δ¹⁸O values are lower, indicating possibly a result of carbonates dissolution. Calculated δ¹⁸O of the fluid in equilibrium with calcite vary from –3.1‰ to –0.1‰, combining the δDV-SMOW (–100‰ to –81‰), implying a fluid mixing of a brine fluid and meteoric water or diagenetic pore water for the mineralization of the Hehuashan deposit.

Sahlström, Fredrik, Chang, Zhaoshan, Arribas, Antonio, Dirks, Paul, Johnson, Craig A., Huizenga, Jan Marten, and Corral, Isaac (2020) Reconstruction of an early Permian, sublacustrine magmatic-hydrothermal system: Mount Carlton epithermal Au-Ag-Cu deposit, Northeastern Australia. Economic Geology, 115 (1). pp. 129-152.
The Mt. Carlton Au-Ag-Cu deposit, northern Bowen basin, northeastern Australia, is an uncommon example of a sublacustrine hydrothermal system containing economic high-sulfidation epithermal mineralization. The deposit formed in the early Permian and comprises vein- and hydrothermal breccia-hosted Au-Cu mineralization within a massive rhyodacite porphyry (V2 open pit) and stratabound Ag-barite mineralization within volcano-lacustrine sedimentary rocks (A39 open pit). These orebodies are all associated with extensive advanced argillic alteration of the volcanic host rocks. Stable isotope data for disseminated alunite (δ34S = 6.3–29.2‰; δ18OSO4 = –0.1 to 9.8‰; δ18OOH = –15.3 to –3.4‰; δD = –102 to –79‰) and pyrite (δ34S = –8.8 to –2.7‰), and void-filling anhydrite (δ34S = 17.2–19.2‰; δ18OSO4 = 1.8–5.7‰), suggest that early advanced argillic alteration formed within a magmatic-hydrothermal system. The ascending magmatic vapor (δ34SSS ≈ –1.3‰) was absorbed by meteoric water (~50–60% meteoric component), producing an acidic (pH ≈ 1) condensate that formed a silicic → quartz-alunite → quartz-dickite-kaolinite zoned alteration halo with increasing distance from feeder structures. The oxygen and hydrogen isotope compositions of alunite-forming fluids at Mt. Carlton are lighter than those documented at similar deposits elsewhere, probably due to the high paleolatitude (~S60°) of northeastern Australia in the early Permian. Veins of coarse-grained, banded plumose alunite (δ34S = 0.4–7.0‰; δ18OSO4 = 2.3–6.0‰; δ18OOH = –10.3 to –2.9‰; δD = –106 to –93‰) formed within feeder structures during the final stages of advanced argillic alteration. Epithermal mineralization was deposited subsequently, initially as fracture- and fissure-filling, Au-Cu–rich assemblages within feeder structures at depth. As the mineralizing fluids discharged into lakes, they produced syngenetic Ag-barite ore. Isotope data for ore-related sulfides and sulfosalts (δ34S = –15.0 to –3.0‰) and barite (δ34S = 22.3–23.8‰; δ18OSO4 = –0.2 to 1.3‰), and microthermometric data for primary fluid inclusions in barite (Th = 116°– 233°C; 0.0–1.7 wt % NaCl), are consistent with metal deposition at temperatures of ~200 ± 40°C (for Au-Cu mineralization in V2 pit) and ~150 ± 30°C (Ag mineralization in A39 pit) from a low-salinity, sulfur- and metal-rich magmatic-hydrothermal liquid that mixed with vapor-heated meteoric water. The mineralizing fluids initially had a high-sulfidation state, producing enargite-dominated ore with associated silicification of the early-altered wall rock. With time, the fluids evolved to an intermediate-sulfidation state, depositing sphalerite- and tennantite-dominated ore mineral assemblages. Void-filling massive dickite (δ18O = –1.1 to 2.1‰; δD = –121 to –103‰) with pyrite was deposited from an increasingly diluted magmatic-hydrothermal liquid (≥70% meteoric component) exsolved from a progressively degassed magma. Gypsum (δ34S = 11.4–19.2‰; δ18OSO4 = 0.5–3.4‰) occurs in veins within postmineralization faults and fracture networks, likely derived from early anhydrite that was dissolved by circulating meteoric water during extensional deformation. This process may explain the apparent scarcity of hypogene anhydrite in lithocaps elsewhere. While the Mt. Carlton system is similar to those that form subaerial high-sulfidation epithermal deposits, it also shares several key characteristics with magmatic-hydrothermal systems that form base and precious metal mineralization in shallow-submarine volcanic arc and back-arc settings. The lacustrine paleosurface features documented at Mt. Carlton may be useful as exploration indicators for concealed epithermal mineralization in similar extensional terranes elsewhere.

Wang, Yong, Tang, Juxing, Wang, Liqiang, Huizenga, Jan Marten, Santosh, M., Zheng, Silun, Hu, Yu, and Gao, Teng (2020) Geology, geochronology and geochemistry of the Miocene Jiaoxi quartz vein-type W deposit in the western part of the Lhasa Terrane, Tibet: implications for ore genesis. Ore Geology Reviews, 120. 103433.
The Jiaoxi deposit is the first Miocene quartz vein-type W deposit discovered in the western part of the Lhasa Terrane comprising with 39,000 metric tons of WO3. The mineralization occurs in wolframite-bearing hydrothermal tensional quartz veins and is associated with Miocene granites. The mineralization event can be divided into an early quartz-oxide stage succeeded by a sulfide stage, and a final fluorite-carbonate stage. Magmatic intrusions at the deposit include biotite monzogranite porphyry, biotite monzogranite, granite porphyry, and muscovite granite at depth and show crystallization ages ranging between 14.5 and 13.7 Ma. Whole-rock geochemistry shows that the intrusions are alkali-rich peraluminous granites that experienced strong fractional crystallization. The most evolved muscovite granite has high W, Nb and Cs contents and is considered to be the source for mineralization. During the late crystallization stage of the highly fractionated muscovite granite, exsolved hydrothermal fluids interacted with the muscovite granite magma and migrated along extensional fractures forming the Jiaoxi deposit. Zircon grains from the granites show uniform εHf (t) values with a wide range between −7.08 and +3.87. The granites have initial Sr isotopic compositions ranging between 0.7094 and 0.7124 and negative εNd (t) values ranging between −4.9 and −9.4. The Sr-Nd-Hf isotope data indicate that the granites were derived from partial melting of a crustal source with minor contributions from the lithospheric mantle. The 3He/4He ratios for wolframite and pyrite vary between 0.30 and 0.74 Ra (Ra = 1.4 × 10–6 for air), confirming that W was mainly sourced from the crust. Collectively, the regional geology, geochronology and geochemistry, indicate that the Miocene post-collisional peraluminous granites and associated W mineralization were triggered by the roll-back and gradual break-off of the northward-subducting Indian continental lithosphere slab. The less evolved biotite monzogranite porphyry, which contains ore-bearing veins and local greisen alteration, appears to be unrelated to W mineralization.

Sims, Kearrin (2020) The ADB and AIIB: cooperation, competition and contestation. In: Jakupec, Viktor, Kelly, Max, and Makuwira, Jonathan, (eds.) Rethinking Multilateralism in Foreign Aid: beyond the neoliberal hegemony. Routledge Explorations in Development Studies . Routledge, New York, NY, USA, pp. 145-159.
The push for greater infrastructure connectivity within the Asia-Pacific as a mechanism for advancing socio-economic development is supported by all the region's nation-states, multilateral development banks operating in the region, and also regional intergovernmental organisations such as the Association of Southeast Asian Nations, South Asian Association for Regional Cooperation, and the Pacific Islands Forum Secretariat. This chapter explores emergent forms of competition, collaboration, and cooperation between Asia’s two largest multilateral development banks: the Asian Infrastructure Investment Bank and the Asian Development Bank. It goes on to analyse the geopolitics that inform the works of these two institutions; how these institutions frame the relationship between infrastructure connectivity and socio-economic progress; and key similarities and differences in their operational structures and funding priorities. Following this geopolitical and operational analysis, the chapter then briefly turns to some of the ways in which Asian Infrastructure Investment Bank and Asian Development Bank development projects and discourse are producing new forms of marginalization, disadvantage, and impoverishment. The benefit and harm of growing regional interconnectivity within the Asia-Pacific is not evenly distributed.

Slezak, Paul, and Spandler, Carl (2020) Petrogenesis of the Gifford Creek Carbonatite Complex, Western Australia. Contributions to Mineralogy and Petrology, 175. 28.
The 1370 Ma Gifford Creek Carbonatite Complex (GCCC) comprises a diverse suite of alkaline dyke and sill complexes that cover an area of similar to 250 km(2) in the Gascoyne Province, Western Australia. Most carbonatite types are interpreted to be related products of fractional crystallisation, with calcite carbonatites representing cumulate rocks and dolomite carbonatites representing crystallised products of the derivative liquids. Genetic relationships between these carbonatites and other alkaline igneous units are less clear. The ankerite-siderite carbonatites and magnetite-biotite dykes are likely of related magmatic origin as both have distinctly high LREE and low HFSE contents. The ankerite-siderite carbonatites have mantle-like delta C-13 isotope values of - 6.1 to - 7.1 parts per thousand and similar geochemistry to other known magmatic ferrocarbonatites. Silica-rich alkaline veins found near the centre of the complex have trace element signatures that are antithetic to the magnetite-biotite dykes, so these veins are interpreted to represent products of alkali- and F-rich magmatic-hydrothermal fluids exsolved from the magnetite-biotite dykes during their emplacement. Carbon, O, Sr, and Nd isotope data are consistent with an enriched mantle source for the origin of the GCCC, with mantle enrichment likely caused by plate convergence processes associated with the c. 2.0 Ga Glenburgh Orogeny. There is no evidence to link mantle plume activity with formation of the GCCC; rather, alkaline magmatism is interpreted to result from low degree melting of the metasomatised mantle during reactivation of the crustal suture zone at 1370 Ma. The carbonatitic magmas utilised the Lyons River Fault to traverse the crust to be emplaced as the GCCC. Post magmatic alteration has variably modified the O and Sr isotope compositions of carbonates from these rocks. We therefore appeal for careful evaluation of isotopic data from ancient carbonatites, as isotopic resetting may be more common than currently recognised.

Oliver, Danielle P., Li, Yasong, Orr, Ryan, Nelson, Paul, Barnes, Mary, McLaughlin, Michael J., and Kookana, Rai S. (2020) Sorption behaviour of per- and polyfluoroalkyl substances (PFASs) in tropical soils. Environmental Pollution, 258. 113726.
The sorption behaviour of three perfluoroalkyl substances (PFASs), namely perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS), was determined on 28 tropical soils. Tropical soils are often highly weathered, richer in sesquioxides than temperate soils and may contain variable charge minerals. There are little data on sorption of PFASs in tropical soils. The highest Kd values were found for PFOS with mean values ranging from 0 to 31.6 L/kg. The Kd values for PFOA and PFHxS ranged from 0 to 4.9 L/kg and from 0 to 5.6 L/kg, respectively. While these values are in the range of literature sorption data, the average Kd values for PFOS and PFOA from the literature were 3.7 times and 3.6 times higher, respectively, than those measured in this study. Stepwise regression analysis did explain some of the variance, but with different explanatory variables for the different PFASs. The main soil properties explaining sorption for PFOS and PFOA were oxalate-extractable Al and pH, and for PFHxS was pH.

Duvert, Clement, Hutley, Lindsay B., Birkel, Christian, Rudge, Mitchel, Munksgaard, Niels C., Wynn, Jonathan G., Setterfield, Samantha A., Cendon, Dioni, and Bird, Michael I. (2020) Seasonal shift from biogenic to geogenic fluvial carbon caused by changing water sources in the wet-dry tropics. Journal of Geophysical Research: Biogeosciences, 125 (2). e2019JG005384.
The riverine export of carbon is expected to be driven by changes in connectivity between source areas and streams. Yet we lack a thorough understanding of the relative contributions of different water sources to the dissolved carbon flux, and of the way these contributions vary with seasonal changes in flow connectivity. Here we assess the temporal variations in water and associated dissolved inorganic carbon (DIC) sources and fluxes in a wet-dry tropical river of northern Australia over two years. We use linear mixing models integrated into a Bayesian framework to determine the relative contributions of rainfall, seasonal wetlands, shallow groundwater, and a deep carbonate aquifer to riverine DIC fluxes, which we relate to the age of water sources. Our results suggest extreme shifts in water and DIC sources between the wet and dry seasons. Under wet conditions, most DIC was of biogenic origin and transported by relatively young water sources originating from shallow groundwater and wetlands. As rainfall ceased, the wetlands either dried out or became disconnected from the stream network. From this stage, DIC switched to a geogenic origin, nearly entirely conveyed via older water sources from the carbonate formation. Our findings demonstrate the importance of changing patterns of connectivity when evaluating riverine DIC export from catchments. This work also illustrates the need to systematically partition DIC fluxes between biogenic and geogenic sources, if we are to quantify how the riverine export of carbon affects net carbon soil storage.

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