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Research Fields

Geochemistry

Research Fellows/Professors︰Sun-Lin ChungDer-Chuen LeeKuo-Lung WangMao-Chang LiangKuo-Fang HuangKwan-Nang PangChing-Chou FuYi-Wei Liu
Research Scientists︰Yoshiyuki IizukaHao-Yang Lee

The institute has state-of-the-art geochemical facilities including but not limited to a nanoscale secondary ion mass spectrometer, thermal ionization mass spectrometers, multi-collector inductively coupled plasma – mass spectrometers, quadrupole inductively coupled plasma – mass spectrometers, gas source mass spectrometers, isotope ratio mass spectrometers, laser absorption spectrometers, X-ray fluorescence analyzers, and electron probe micro-analyzers. With these instruments, the concentration and isotopic composition for certain elements in a wide variety of solid, liquid and gaseous samples can be accurately and precisely measured. Our researchers have employed short-lived radionuclides and high-precision isotopic geochemistry to study the origin and early evolution of the solar system. The institute has developed analytical methods for geochronology and geochemistry of igneous rocks that are powerful tools in research related to orogeny. These methods have also been applied to a variety of igneous, metamorphic and mantle rocks in Taiwan and overseas for comparative research.

The institute has also developed analytical methods for triple oxygen isotopes and clumped isotopes that, when combined with marine geochemistry and biogeochemistry, contribute to the reconstruction of paleoclimate and paleoenvironment. Recently, tackling regional and global biogeochemical cycles of greenhouse gases such as carbon dioxide has become a focus of the Institute. Our researchers also involved in monitoring volcanic and seismic hazards using fluid geochemistry; for example, soil radon and carbon dioxide have been used to trace fault and seismic activity. Topics related to archaeological sciences include jade, bronze objects, coins and glass beads unearthed in East and Southeast Asia. To be able to obtain key samples and acquire high-quality data out of them are very important in geochemistry research. Our researchers actively seek international collaboration in doing so and undertake fieldwork to collect samples suitable for the research topics listed above.

Research Highlights

An Automatic System for Continuous Monitoring and Sampling of Groundwater Geochemistry in Earthquake-Prone Regions of SW Taiwan
An Automatic System for Continuous Monitoring and Sampling of Groundwater Geochemistry in Earthquake-Prone Regions of SW Taiwan
Previous studies have revealed that gas compositions of fluid samples collected from southwestern Taiwan, where many hot springs and mud volcanoes are distributed along with tectonic structures, show significant variation before and after some disaster seismic events. Such variations, including radon activity, CH4/CO2, and 3He/4He ratios of gas compositions, are considered precursors of earthquakes in this area. An automatic system for continuous on-line gas monitoring and groundwater sampling was established at Yun-Shui (YS), where an artesian well located at an active fault zone in SW Taiwan, to validate the relationship between fluid compositions and seismicity. It is equipped with a quadrupole mass spectrometer (QMS) and a radon detector for in-situ measurement of the dissolved gas composition. Variations of dissolved gas compositions are transmitted to the laboratory through the internet. Furthermore, a syringe pump apparatus for the retrieval and temporal analysis of helium (SPARTAH) is also installed for off-line laboratory analysis for obtaining the detailed time-series records of helium, hydrogen, oxygen, and dissolved inorganic carbon (DIC) isotopic compositions as well as dissolved inorganic carbon and chloride concentration of water samples at this station. After continuous monitoring for several months, two substantial anomalies of multiparameter were observed prior to the significant earthquakes. This automated system has been demonstrated to be feasible for long-term continuous seismo-geochemical research in this area.
Fu, Ching-Chou
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Regulation of calcification site pH is a polyphyletic but not always governing response to ocean acidification
Regulation of calcification site pH is a polyphyletic but not always governing response to ocean acidification
The response of marine-calcifying organisms to ocean acidification (OA) is highly variable, although the mechanisms behind this variability are not well understood. Here, we use the boron isotopic composition (δ11B) of biogenic calcium carbonate to investigate the extent to which organisms’ ability to regulate pH at their site of calcification (pHCF) determines their calcification responses to OA. We report comparative δ11B analyses of 10 species with divergent calcification responses (positive, parabolic, threshold, and negative) to OA. Although the pHCF is closely coupled to calcification responses only in 3 of the 10 species, all 10 species elevate pHCF above pHsw under elevated pCO2. This result suggests that these species may expend additional energy regulating pHCF under future OA. This strategy of elevating pHCF above pHsw appears to be a polyphyletic, if not universal, response to OA among marine calcifiers—although not always the principal factor governing a species’ response to OA.
Liu, Yi-Wei
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Tracing Argoland in eastern Tethys and implications for India-Asia convergence
Tracing Argoland in eastern Tethys and implications for India-Asia convergence
Incremental accretion of continental fragments from East Gondwana to Eurasia resulted in the growth of Asia and rise of the Tibetan Plateau, yet its detailed evolution remains uncertain. Argoland, a continental fragment that rifted from NW Australia during the Late Jurassic, played a key role in the initial opening of the Indian Ocean and the evolution of eastern Tethys. However, its present identity remains elusive, with East Java-West Sulawesi currently assumed to be the most likely option. To constrain the missing Argoland and its role in India-Asia convergence, we report new detrital zircon data from Sulawesi, Indonesia, and West Burma, Myanmar, and synthesize literature results from relevant regions in Southeast Asia, which (>15,000) reveal age profiles of West Sulawesi, the central Sulawesi metamorphic belt, and southeast Borneo comparable to that of Bird's Head, New Guinea, whereas age patterns of West Burma and East/West Java are similar to those of NW Australia. Notably, the most dominant age populations in NW Australia are rarely detected in Sulawesi and Borneo. These observations, combined with previous geological records and recent paleomagnetic data, suggest that West Burma is the mysterious Argoland, opposing the currently favored East Java-West Sulawesi model, with East Java and West Sulawesi probably having originated from NW Australia and Bird's Head, respectively. We estimate an average northward motion of ∼6–8 cm/yr for West Burma, which split from NW Australia to approach the equator during ca. 155–95 Ma, shedding new light on the reconstruction and breakup of northern East Gondwana, progressive building of Southeast Asia, and India-Asia convergence.
Chung, Sun-Lin
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Tracing local sources and long-range transport of PM10 in central Taiwan by using chemical characteristics and Pb isotope ratios
Tracing local sources and long-range transport of PM10 in central Taiwan by using chemical characteristics and Pb isotope ratios
Central Taiwan is among the most heavily polluted regions in Taiwan because of a complex mixing of local emissions from intense anthropogenic activities with natural dust. Long-range transport (LRT) of pollutants from outside Taiwan also contributes critically to the deterioration of air quality, especially during the northeast monsoon season. To identify the sources of particulate matter < 10 μm (PM10) in central Taiwan, this study performed several sampling campaigns, including three local events, one LRT event, and one dust storm event, during the northeast monsoon season of 2018/2019. The PM10 samples were analyzed for water-soluble ion and trace metal concentrations as well as Pb isotope ratios. Local sediments were also collected and analyzed to constrain chemical/isotopic signatures of natural sources. The Pb isotope data were interpreted together with the enrichment factors and elemental ratios of trace metals in PM10, and reanalysis data sets were used to delineate the sources of PM10 in central Taiwan. Our results suggested that Pb in PM10 was predominantly contributed by oil combustion and oil refineries during the local events (48–88%), whereas the lowest contributions were from coal combustion (< 21%). During periods of high wind speed, the contribution from natural sources increased significantly from 13 to 31%. Despite Pb represented only a small portion of PM10, a strong correlation (r = 0.89, p  < 0.001, multiple regression analysis) between PM10 mass and the concentrations of Pb, V, and Al was observed in the study area, suggesting that the sources of PM10 in central Taiwan can be possibly tracked by using chemical characteristics and Pb isotopes in PM10. Moreover, the Pb isotopic signals of PM10 collected during the LRT event confirmed the impact of LRT from Mainland China, and the chemical characteristics of the PM10 significantly differed from those of the PM10 collected during local events. This study demonstrates the robustness of using a combination of Pb isotopic compositions and chemical characteristics in PM10 for source tracing in complex and heavily polluted areas.
Huang, Kuo-Fang
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Diachronous initiation of post-collisional magmatism in the Arabia-Eurasia collision zone
Diachronous initiation of post-collisional magmatism in the Arabia-Eurasia collision zone
The continental collision between Arabia and Eurasia which gave rise to the Caucasus-Iran-Anatolia (CIA) volcanic province provides a unique opportunity for understanding collisional zone magmatism. This study reports a comprehensive dataset of ages and geochemical compositions of volcanic rocks formed during the initial phase of post-collisional magmatism in the CIA province. The age data indicate a diachronous onset of volcanism that began ~17 Ma in SE Anatolia, and propagated northward from ~11 to 9 Ma toward NE Anatolia and NW Iran. The rocks are characteristically bimodal, with dominantly basic (SiO2 = 48–52 wt%) and silicic (SiO2 = 58–71 wt%) components that feature significant isotopic variations (εNd = +6 to −5), suggesting two principal magma sources: (1) a juvenile mantle-derived component, and (2) an older continental crust component. We therefore attribute the volcanic initiation to a migrating post-collisional extension regime caused by the successive breakoff of subducted Neo-Tethyan slabs. Subsequent volcanism that began from ~6.5 Ma resulted in a wide spectrum of calc-alkaline and alkaline rocks, with mafic to felsic lithologies in the entire province. From ~2 Ma, volcanism ceased in the western CIA province, and started propagating eastward and southeastward to SE Iran, following the Urumieh-Dokhtar magmatic belt, consistent with the notion of an oblique continental collision between Arabia and Eurasia.
Chung, Sun-Lin
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A coastal coccolithophore maintains pH homeostasis and switches carbon sources in response to ocean acidification
A coastal coccolithophore maintains pH homeostasis and switches carbon sources in response to ocean acidification
Ocean acidification will potentially inhibit calcification by marine organisms; however, the response of the most prolific ocean calcifiers, coccolithophores, to this perturbation remains under characterized. Here we report novel chemical constraints on the response of the widespread coccolithophore species Ochrosphaera neapolitana (O. neapolitana) to changing-CO2 conditions. We cultured this algae under three pCO2-controlled seawater pH conditions (8.05, 8.22, and 8.33). Boron isotopes within the algae’s extracellular calcite plates show that this species maintains a constant pH at the calcification site, regardless of CO2-induced changes in pH of the surrounding seawater. Carbon and oxygen isotopes in the algae’s calcite plates and carbon isotopes in the algae’s organic matter suggest that O. neapolitana utilize carbon from a single internal dissolved inorganic carbon (DIC) pool for both calcification and photosynthesis, and that a greater proportion of dissolved CO2 relative to HCO3− enters the internal DIC pool under acidified conditions. These two observations may explain how O. neapolitana continues calcifying and photosynthesizing at a constant rate under different atmospheric-pCO2 conditions.
Liu, Yi-Wei
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Mid-Miocene volcanic migration in the westernmost Sunda arc induced by India-Eurasia collision
Mid-Miocene volcanic migration in the westernmost Sunda arc induced by India-Eurasia collision
The migration of arc magmatism that is a fundamental aspect of plate tectonics may reflect
the complex interaction between subduction zone processes and regional tectonics. Here we
report new observations on volcanic migration from northwestern Sumatra, in the westernmost
Sunda arc, characterized by an oblique convergent boundary between the Indo-Australian
and Eurasian plates. Our study indicates that in northwestern Sumatra, volcanism ceased at
15–10 Ma on the southern coast and reignited to form a suite of active volcanoes that erupt
exclusively to the north of the trench-parallel Sumatran fault. Younger volcanic rocks from the
north are markedly more enriched in K2O and other highly incompatible elements, delineating
a geochemical variation over space and time similar to that in Java and reflecting an increase
in the Benioff zone depth. We relate this mid-Miocene volcanic migration in northwestern
Sumatra to the far-field effect of propagating extrusion tectonics driven by the India-Eurasia
collision. The extrusion caused regional deformation southward through Myanmar to northwestern Sumatra and thus transformed the oblique subduction into a dextral motion–governed
plate boundary. This tectonic transformation, associated with opening of the Andaman Sea, is
suggested to be responsible for the volcanic migration in northwestern Sumatra.
Chung, Sun-Lin
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Magnesium isotopic systematics of the Makran arc magmas, Iran: Implications for crust-mantle Mg isotopic balance
Magnesium isotopic systematics of the Makran arc magmas, Iran: Implications for crust-mantle Mg isotopic balance
Continental crust loses Mg by lower crustal foundering and chemical weathering to become its intermediate-silicic composition. Both processes should preferentially retain heavy Mg isotopes in the crust, yet the estimated Mg isotopic ratio for the bulk continental crust is indistinguishable from that for unmodified mantle. This can be elucidated by two notions that are not mutually exclusive: (i) the basaltic parent to the crust has Mg isotopes lighter than the mantle and has since become mantle-like as a result of Mg loss by igneous and weathering fractionation, and (ii) heavy Mg isotopes in the continental crust are constantly balanced by a hidden input of light Mg isotopes. Arc magmas are arguably building blocks of the continental crust and their Mg isotopic signature could be used to place limits on the above views. Here, we conducted a Mg isotopic study of the Makran arc, a rare continental arc in Iran within the Alpine-Himalayan orogenic belt. The measured Mg isotopic ratios for most mafic and intermediate samples are mantle-like with δ26Mg values ranging from −0.32‰ to −0.20‰. After excluding dubious samples affected by alteration, the silicic samples span a broad range of isotopic ratios with δ26Mg values ranging from −0.32‰ to +0.32‰, beyond that of unmodified mantle (δ26Mg = −0.25 ± 0.04‰). The isotopic data form a trend from mantle-like δ26Mg at relatively high MgO towards elevated δ26Mg at low MgO, requiring the isotopic variability be related to differentiation in an open system involving assimilation of high-δ26Mg crustal rocks. Our results are generally consistent with Mg isotopic data compiled for global arcs where magmas have Mg isotopic ratios ranging from mantle-like to ∼0.7 per mil above the mantle range, and compositions substantially below that range are rare. Thus, heavy Mg isotopes in the continents predicted by igneous and weathering fractionation might have been compensated by a hidden input of light Mg isotopes, which is presumably in the form of carbonates, leading to a bulk crustal Mg isotopic composition that is mantle-like.
Pang, Kwan-Nang
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In-situ U–Pb dating of monazite, xenotime, and zircon from the Lantian black shales: Time constraints on provenances, deposition and fluid flow events
In-situ U–Pb dating of monazite, xenotime, and zircon from the Lantian black shales: Time constraints on provenances, deposition and fluid flow events
The Lantian formation, located in eastern South China block (SCB), forms the lower sequence of the Ediacaran period, at the transition from Proterozoic to Paleozoic. The fossils of Lantian formation have been proposed to predate the Avalon biota (about 579–565 Ma), the earliest known fossil assemblages with complex morphologies, based largely on stratigraphy. Mineral chemistry and in-situ U–Pb dating of monazites, xenotimes, and zircons from the black shale in fossil-rich zone are studied for the first time to provide critical age constraints for provenance, early diagenesis and fluid flow events. Detrital zircons and monazites give age populations similar to that of the Doushantuo formation, indicative of the same provenances for Ediacaran basins throughout the SCB. The low-Y monazites formed during early diagenesis yield a weighted mean age of 612 ± 29 Ma (n = 9, MSWD = 3.1). Age spectrum of analyzed monazites demonstrated that the sedimentation started from at least around 645 Ma. Subsequently, the overprinting events could be recorded by xenotimes and zircons precipitated from fluids during late diagenesis. Age results from xenotimes ranging from 441 Ma and 585 Ma were contemporaneous with the timing of collision of SCB with Gondwanaland, and a weighted mean age of 394.8 ± 3.7 Ma (n = 23, MSWD = 2.8) obtained from diagenetic zircons could be correlated to the post-tectonic granites widespread on the SCB. The pre-existing monazites generally remain pristine, and the multi-staged fluids were locally interacted with the samples to form Th-rich domains in monazites.
Lee, Der-Chuen
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Tracking the magmatic response to subduction initiation in the forearc mantle wedge: Insights from peridotite geochemistry of the Guleman and Kızıldağ ophiolites, Southeastern Turkey
Tracking the magmatic response to subduction initiation in the forearc mantle wedge: Insights from peridotite geochemistry of the Guleman and Kızıldağ ophiolites, Southeastern Turkey
The initiation of subduction is associated with sequential magmatic responses that lead to the formation of the forearc lithosphere, yet the detailed characteristics of these magmatic activities are not well constrained. Here we use mineral chemistries and bulk-rock trace-element contents of highly-depleted harzburgites from the Guleman and Kızıldağ ophiolites in Southeast Turkey to examine mantle wedge melting dynamics during subduction initiation. We focus on how different components from the subducting slabs potentially contribute to various stages of magmatism throughout the process. Mineral and bulk-rock compositions of these harzburgites are significantly different from those of abyssal peridotites, suggesting that our harzburgites cannot be explained as residues of anhydrous adiabatic melting and melt-rock interaction at mid-ocean ridges alone. This implies that the petrogenesis of SE Turkey harzburgites involves additional processes and components. Harzburgites with the most depleted heavy-rare earth element (HREE) contents are the ones with the highest abundance of strongly incompatible elements, which can be explained by open-system processes where the peridotites in the mantle wedge experienced melting and infiltration of enriched components simultaneously. Open-system dynamic melting models with continuous flux of sediment-derived melts can account for the observed correlation, but are numerically too low compared to the measured values. Based on the observed fractionation between Zr, Hf, and elements with similar incompatibility (middle REEs), we hypothesized the involvement of amphibolite-derived melt and modeled its numerical trace-element contents. Binary mixing between this hypothetical melt and residues of the former open-system model can coherently account for the majority of the obtained trace-element data. This indicates that magmatic events during subduction initiation likely involve multiple components and occur in multiple stages, and that melt-mantle interaction plays a significant role in oceanic forearc lithosphere formation. Based on our model, we suggest the high (Zr/MREE)N signatures in some boninites and depleted harzburgites found in modern forearcs and ophiolites could be inherited from amphibolite-derived melts. Moreover, the existence of slab melts agrees with current constraints on the reconstructed geothermal gradients during subduction initiation based on the petrology and geochemistry of metamorphic soles.
Wang, Kuo-Lung
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Utilization of Δ17O for nitrate dynamics in a subtropical freshwater reservoir
Utilization of Δ17O for nitrate dynamics in a subtropical freshwater reservoir
Feitsui Reservoir, a freshwater body in Taiwan with minimal anthropogenic stress, meets the water demand for the population of more than five million living in Taipei city. In view of the biogeochemical processes controlling the long-term trophic status of this socio-economically and ecologically important aquatic system, probing the nitrogen cycle and its dynamics is essential. Here, we monitored the concentration and stable isotopic compositions (δ15N, δ18O, and Δ17O) of nitrate in the Feitsui Reservoir and in the atmospheric wet deposition at intervals of 1–2 weeks for a year, along with measurements of environmental data such as chlorophyll a, dissolved oxygen, and community respiration. Emphasis was laid on Δ17O (= δ17O – 0.52 × δ18O) because of the mass-conservative behavior of Δ17O during partial assimilation and denitrification. The present approach offered an effective method to quantify the gross nitrification and removal/uptake rates of nitrate in the reservoir. The atmospheric nitrate exhibited elevated Δ17O values ranging from 12.6‰ to 30.1‰ (23.3 ± 5.0‰), compared to the lower Δ17O values of ~0 to 4.6‰ (1.1 ± 0.7‰) recorded in the reservoir nitrate. Utilizing Δ17O for dissolved nitrates, we observed a seasonal trend of higher nitrification and removal rates during the summer than in the winter. Our estimates showed annually-averaged nitrification rate of 55 ± 11 mmol m−2 d−1 and removal/uptake rate of 57 ± 11 mmol m−2 d−1 (or a nitrate turnover time of ~2.5 months), representing the active nature of nitrogen cycling in this preserved subtropical reservoir.
Liang, Mao-Chang
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