Hao-Yang Lee

Products of explosive volcanism can be transported into the oceans, where they form marine tephra layers. The processes responsible for their deposition are often complex, involving multiple transport mechanisms. During the RV Investigator voyage IN2022‐V02 (2022), a 35‐cm‐thick marine tephra unit was piston‐cored at 2,460 m water depth in the Havre Trough, north of New Zealand. The unit grades from planar laminated medium sand at the base to cross‐laminated fine sand and massive sandy silt at the top. It is composed predominantly of elongated (tube‐shaped), vesicular, curviplanar rhyolitic glass shards, with rare lithic clasts and pyroxene and feldspar fragments enriched at the base. Planktic foraminifera occur as intact bioclasts, increasing upward from 1 to 20 vol.%. The homogeneous major and trace element composition of glass shards throughout the sequence indicates a juvenile origin from a single volcanic event. Geochemical fingerprinting identified the Macauley Volcano, located ∼100 km from the core site, as the most likely source. The stratigraphy and vertical arrangement of the bedforms are consistent with a model of sedimentation by subaerial eruption plume fallout and/or pyroclastic density currents traveling over the ocean, followed by vertical density currents through the water column that eventually transformed into seafloor‐hugging turbidity currents upon impact on the seafloor. Our results demonstrate that the sedimentary history of primary marine tephra associated with large magnitude eruptions may be complex and include vertical density currents. This sedimentation regime may significantly contribute to the lateral variation in the thickness of marine marker tephra layers.

Situated in the Cabo Verde Archipelago, Fogo is among the most active oceanic volcanoes in the Atlantic, hosting frequent eruptions some of which were highly explosive and at least one gravitational flank collapse in the last 100 kyr. This study presents new volcanic glass shard geochemical data with high spatial distribution from 54 sites comprising samples from both pre- and post-collapse times. The analyzed glasses comprise basanites, tephrites, and foidites with a subset extending into the phonolite field. The glass compositions complement bulk rock data particularly in the range between 6 and 1 wt.% MgO, thus enabling more detailed inter-dataset comparison. Major and trace element data reveal five geochemical Groups characterized by incompatible element contents partly delineating rock series. Compositional diversity is primarily controlled by fractional crystallization, and to lesser extents by mantle-source heterogeneity and degrees of partial melting. A geochemical framework is established for investigating provenance of ash and volcaniclastics in the Cabo Verde region and beyond by integrating new glass data with published bulk rock and tephra records. We validate the classification scheme through comparison with primary marine tephra deposits, demonstrating robust sample assignment to the observed compositional Groups. The new provenance data go beyond simple attribution to Fogo by resolving distinct compositional Groups, enabling improved discrimination within Fogo-derived material. Group assignment and characterization of differentiation trends provide a useful first-order indication of pre- versus post-collapse affinity. The glass dataset serves as a reference for future provenance and source correlation studies across the Cabo Verde Archipelago.

Cenozoic India-Asia collision fundamentally reconfigured the geomorphology of Southeast Asia, triggering a profound reorganization of major river networks in response to the uplift of the Tibetan Plateau and associated regional deformation. Previous studies have suggested that the upper Yangtze River once drained southward into the Red River prior to the Late Miocene, after which the sediment provenance of the Red River was considered largely stable. However, this interpretation lacks critical constraints from the thick Cenozoic succession preserved in the Hanoi Basin. This study applies detrital zircon U-Pb geochronology to borehole samples from the Hanoi Basin. New data are integrated with published datasets and analyses of modern river sands from Yen Bai, upstream of major confluences, to evaluate spatio-temporal provenance variations and reconstruct the Neogene evolution of the Red River system.Our results reveal that sediment provenance upstream of major confluences has remained broadly consistent, whereas the Hanoi Basin records distinct shifts since the Late Miocene. Detrital zircon age signatures indicate that the Ailao Shan-Red River Shear Zone (ASRRSZ), the Phan Si Pan Uplift, and the Song Chay Dome were important sediment sources for the Hanoi Basin, with fluctuations in their relative contributions reflecting drainage reorganization. Incorporation of the Lo River into the Red River occurred by the Late Miocene, followed by integration of the Da River in the early Pliocene. This Neogene reorganization of the Red River system reflects progressive expansion of the catchment, likely driven by kinematic reversal along the ASRRSZ and concurrent climate change.

The Meguma Terrane of the Northern Appalachians is primarily composed of Cambro-Ordovician metapelites and metapsammites that were intruded by Late Devonian (380–360 Ma) granitic plutons. The Port Mouton Pluton (373 ± 1 Ma) is composed of tonalite and monzogranite, contains silicic microgranular enclaves and is cross-cut by lamprophyric dykes. The silicic enclaves are peraluminous, magnesian and calc-alkalic to calcic. The enclaves can be divided into two groups. The Group 1 enclaves are temporally, compositionally and isotopically ( ε N d 373 = −1.2 to +1.5) similar to the host Port Mouton Pluton (PMP). The Group 2 enclaves are Si-rich (SiO ₂ = 74.3–79.7 wt%) and Al-poor (Al ₂ O ₃ = 10.0–12.2 wt%). The youngest zircons are of Early Cambrian age (529 ± 6 Ma) and the rocks are isotopically different ( ε N d 530 = −6.7 to −6.4). MELTS modelling ( P = 3 kbar; ƒO ₂ = NNO = +1; H ₂ O = 2.00 wt%) shows that fractional crystallization can generate the range of PMP rock compositions. The parental magma of the PMP was probably derived by partial melting of sub-Meguma Terrane rocks in a lower crustal hot zone over a 20–30 myr time period. The Group 2 enclaves are xenoliths derived by melting of metasedimentary upper crustal rocks of Avalonia.

Chihsing Volcano represents the youngest and highest edifice within the Tatun Volcano Group (TVG) of northern Taiwan, yet the timing and character of its recent magmatic activity have remained poorly constrained. This study integrates 40Ar/39Ar and 14C geochronology, mineral chemistry, whole-rock geochemistry, and Sr–Nd isotopes from drill cores to reconstruct late-stage evolution of the volcano. Our results establish a two-stage eruptive model for the Late Pleistocene to Early Holocene transition. The first stage (16–8 ka) featured magmatic eruptions producing calc-alkaline andesitic lava flows. 40Ar/39Ar ages (14.0 ± 2.2 to 11.6 ± 3.6ka) mark these as TVG's youngest reliably dated magmatic units, demonstrating persistence far later than previously recognized. Mineral thermobarometry and geochemistry indicate origin from a homogeneous 7–15 km deep crustal reservoir (1135–1184°C) with repeated recharge events producing thorough magma homogenization evidenced by narrow isotopic (εNd = +2 to +3) and geochemical ranges, and negligible crustal contamination. The second stage (~8 ka) transitioned to phreatic activity. 14C dating of crater-fill sediments confirms sedimentation initiation around 7.4 ka, with rates increasing from 0.02 to 0.17 cm/yr after 3.6 ka. Ongoing phreatic activity continues through residual magmatic heat driving pyroclastic density currents, tephra fallout, and landslides. These findings reveal a persistent magma supply system beneath the TVG and suggest that the potential for magmatic transport remains active. Consequently, future hazard assessments for the Taipei metropolitan area should integrate both phreatic and potential magmatic eruption scenarios.

Large explosive volcanic eruptions from island volcanoes deliver vast quantities of ash to the marine environment. While many of the transport pathways are understood, those from shoreline-crossing or submarine pyroclastic currents, and their transformation into water-supported gravity flows, remain poorly constrained. We report the discovery by International Ocean Discovery Program (IODP) deep drilling of a 200-meter-thick ash megabed buried in rift basins of the South Aegean Volcanic Arc. The >73–cubic kilometer ash deposit originates from the Kos Plateau Tuff caldera-forming eruption, which occurred 161 thousand years ago, >120 kilometers to the east. The ash forms a chemically uniform, graded megabed lacking bioturbation, interpreted as having been emplaced by a stream of eruption-fed turbidity currents. Bioclastic debris within the ash provides evidence of widespread destruction of marine ecosystems. Large volcanic eruptions can remodel the seafloor landscape, deposit thick ash turbidites, and destroy marine biota on island arc–wide scales in short-lived, catastrophic events.

Alp Himalaya Orojenik Kuşağı’nın önemli bir bölümünü oluşturan, Doğu Pontid Orojenik Kuşağı’nda yüzeyleyen Güvendik Dayk Karmaşığı’na ait birimler metagranitler ile temsil edilmektedir. Bu çalışmada inceleme konusu metagranitlere ait zirkon U-Pb jeokronolojisi ve zirkon Lu-Hf izotopları sunulmaktadır. Metagranitler petrografik olarak plajiyoklas, kuvars, K-feldispat, amfibol ve biyotit/muskovit minerallerinden oluşmakta olup granoblastik doku göstermektedir. Zirkon U-Pb jeokronoloji verilerine göre metagranit örneğinin kristalizasyon yaşı 206Pb/238U; 146 ± 13 My, metamorfizma yaşı ise 206Pb/238U verilerine göre 78,3 ± 1,4 My. dır. Magmatik kökenli zirkon minerallerinin 176Lu/177Hf izotop verileri 0,0008 ile 0,0026 aralığında değişmektedir. ƐHf(t) değerleri 6,01 ile 12,7 aralığında değişmekte olup pozitif değerler göstermektedir. TDM2 modal yaşları 0,40-0,81 Milyar yıldır. Metamorfik kökenli zirkon minerallerinin 176Lu/177Hf izotop verileri 0,0009 ile 0,0019 aralığında değişmektedir. ƐHf(t) değerleri 3,8 ile 5,9 aralığında değişmekte olup pozitif değerler sergilemektedir. TDM2 modal yaşları 0,76-0,89 Milyar yıldır. Pozitif ƐHf(t) değerleri metagranitlerin tüketilmiş manto kökeninden geldiğini göstermektedir.

Pontid Orojenik Kuşağı, Bulgaristan’dan başlayıp, Türkiye-Istranca Bölgesi'nden Küçük Kafkasya'ya kadar uzanan Doğu-Batı uzanımlı dağ kuşağını temsil etmektedir. İnceleme alanı Pontidler’in doğu kesiminde (Kaçkar Batoliti) Çamlıkaya köyü (İspir/Erzurum) ve çevresini kapsamaktadır. İnceleme alanında yüzeyleyen plütonik kayaçlar genel olarak granit ve granodiyoritler ile temsil edilmektedir. İncelenen kayaçlar, bileşimsel olarak kalkalkalen’den şoşonitiğe değişen karakterde ve I-tipi granit özelliğindedir. İlksel mantoya göre normalize edilmiş iz element diyagramlarında, Rb, K, Th, Ba gibi büyük iyon yarıçaplı elementlerde zenginleşme olduğu, Nb, Ti, P ve Ta gibi yüksek alan enerjili elementlerde ise fakirleşme olduğu görülmektedir. Granitik kayaçlarda gözlenen negatif Nb anomalisi yitimle ilişkili magmaların karakteristik özelliğidir. Kondrite göre normalize edilmiş iz element diyagramlarında, hafif nadir toprak elementleri, ağır nadir toprak elementlerine göre daha fazla zenginleşme göstermektedir. Negatif Eu anomalileri görülmektedir. Yüksek Rb/Sr, Nb/Ta, Zr/Hf, Th/U, Th/Ta ve düşük Nb/La gibi iz element oranları bu kayaçların oluşumunda kabuksal kirlenmenin etkin rol oynadığını göstermektedir. İnceleme konusunu oluşturan kayaçlar tektonik ayırtlama diyagramlarında volkanik yay ve çarpışma sonrası bölge alanlarına düşmektedir.

We report new U–Pb zircon ages for mafic plutonic (gabbro) and volcanic (andesite) rocks, along with the whole-rock chemistry of a mafic–felsic suite of volcanic rocks from the Siang window of the Eastern Himalayan Syntaxis, NE India. Field relationships, and mineralogical and geochemical characteristics, of the studied mafic–intermediate–felsic rocks suggest their co-magmatic linkage that was generated in an extensional tectonic environment. Incompatible trace elements and low concentrations of large ion lithophile elements (LILEs) and REE behaviour reflect both the enriched nature of the mafic rocks and the limited influence of crustal contamination in their genesis. Partial melting and fractional crystallization processes have played a major role during the genesis of these felsic volcanics from the parental mafic magma. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb ages suggest that the mafic plutonic rock was emplaced at c. 121.18 ± 1 Ma and intermediate volcanic rock was emplaced at c. 135.48 ± 0.50 Ma during the Early Cretaceous period. The new ages are consistent with earlier reported zircon U–Pb ages (133.0 ± 1.9–130.7 ± 1.8 Ma) of felsic volcanic rocks from the present study area. Our new field observations, and mineralogical and geochemical characteristics, in conjunction with the U–Pb isotopic database suggest that the major magmatic event in the core of the Siang window of the Eastern Himalaya is coeval with the Rajmahal–Sylhet–Mikir–Shillong flood basalts of eastern and northeastern India, and the Comei–Bunbury Large Igneous Province of southeastern Tibet and SW Australia. These events are related to the break-up of eastern Gondwana and outbreak of the Kerguelen plume.

The climactic Los Chocoyos (LCY) rhyolitic eruption from Atitlán caldera (Guatemala) is a key chronostratigraphic marker for the Late Quaternary period that has been widely used for relative dating of paleoenvironmental, paleoclimate, and volcanic events throughout Central America and adjacent marine basins in the Pacific Ocean, the Caribbean Sea, and the Gulf of Mexico. Despite LCY tephra being an important marker horizon, a radioisotopic age for this eruption has remained elusive. LCY tephra has been dated at ca. 84 ka BP based on its occurrence in marine sediments with model δ18O ages, but this inferred age has not been independently confirmed through radioisotopic methods. This is due to the inherent limitations of radiocarbon dating (which is practically limited to ˂50 ka) and a lack of suitable materials for 40Ar/39Ar analysis in LCY tephra. To overcome this limitation, we applied 238U-230Th and (U-Th)/He zircon double-dating (ZDD). Due to zircon being alteration-resistant this method establishes absolute chronologies for and correlations between silicic tephra deposits, which are unaffected by glass alteration or complex compositional signatures within a single eruption. 238U-230Th zircon crystallization rim ages were obtained from LCY proximal tephras (~17 km from Atitlán caldera) including sub-units that may bear distinct glass compositions (e.g., fallout, ignimbrite, surge) as well as ultra-distal fallout tephra samples (~300 km from source) collected from drill cores at Petén Itzá Lake (ICDP) and the Pacific Ocean (IODP). All samples yielded zircon with statistically indistinguishable 238U-230Th zircon rim age spectra. These reveal continuous zircon crystallization from ca. 160 ka to ca. 74 ka, with peaks in zircon crystallization between 90-100 ka. ZDD eruption ages from two LCY fallout and one ignimbrite deposit are indistinguishable with error-weighted averages of 75.1 ± 3.2 ka (1σ; n = 16; MSWD = 4.1), 76.0 ± 2.5 ka (n = 16; MSWD = 2.5), and 72.8 ± 3.5 ka (n = 16; MSWD = 3.7). Considering all individual zircon results as a single population, a weighted average ZDD age of 74.8 ± 1.7 (1σ; n = 48; MSWD = 3.3) is obtained and considered as the best estimate for LCY eruption age. GIS-based reassessment of LCY eruptive volume uses thickness information from new 113 outcrops including 6–10 m thick pyroclastic density currents in Chiapas, Mexico (>130 km from the source) and suggests a minimum estimate volume of ~1200 km3, confirming the LCY eruption as the first‐ever recognized supereruption in Central America. The new ZDD age of 74.8 ± 1.7 ka for the LCY eruption is significantly younger than the commonly cited O-isotope stratigraphic age of 84 ± 5 ka. This age is close to the voluminous (2,800-5,600 km3) Young Toba Tuff (YTT) supereruption at ca. 73.8 ± 0.3 ka from Toba Caldera, Indonesia. Both YTT and LCY eruptions have been previously linked to prominent Quaternary climate excursions. Based on the new LCY eruption age, climate-forcing effects that are usually attributed to YTT may in fact be exacerbated by another supereruption occurring within a short time window of the YTT event.