Advancing Santorini’s tephrostratigraphy: new glass geochemical data and improved marine-terrestrial tephra correlations for the past ∼360 kyrs

The island of Santorini in the Aegean Sea is one of the world’s most violent active volcanoes. Santorini has produced numerous highly explosive eruptions over at least the past ∼360 kyrs that are documented by the island’s unique proximal tephra record. However, the lack of precise eruption ages and comprehensive glass geochemical datasets for proximal tephras has long hindered the development of a detailed distal tephrostratigraphy for Santorini eruptions. In light of these requirements, this study develops a distal tephrostratigraphy for Santorini covering the past ∼360 kyrs, which represents a major step forward towards the establishment of a tephrostratigraphic framework for the Eastern Mediterranean region. We present new EPMA glass geochemical data of proximal tephra deposits from twelve Plinian and numerous Inter-Plinian Santorini eruptions and use this dataset to establish assignments of 28 distal marine tephras from three Aegean Sea cores (KL49, KL51 and LC21) to specific volcanic events. Based on interpolation of sapropel core chronologies we provide new eruption age estimates for correlated Santorini tephras, including dates for major Plinian eruptions, Upper Scoriae 1 (80.8 ± 2.9 ka), Vourvoulos (126.5 ± 2.9 ka), Middle Pumice (141.0 ± 2.6 ka), Cape Thera (156.9 ± 2.3 ka), Lower Pumice 2 (176.7 ± 0.6 ka), Lower Pumice 1 (185.7 ± 0.7 ka), and Cape Therma 3 (200.2 ± 0.9 ka), but also for 17 Inter-Plinian events. Older Plinian and Inter-Plinian activity between ∼310 ka and 370 ka, documented in the distal terrestrial setting of Tenaghi Philippon (NE Greece), is independently dated by palynostratigraphy and complements the distal Santorini tephrostratigraphic record

The marine isotope stage 1–5 cryptotephra record of Tenaghi Philippon, Greece:Towards a detailed tephrostratigraphic framework for the Eastern Mediterranean region

The iconic climate archive of Tenaghi Philippon (TP), NE Greece, allows the study of short-term palaeoclimatic and environmental change throughout the past 1.3 Ma. To provide high-quality age control for detailed palaeoclimate reconstructions based on the TP archive, (crypto)tephra studies of a peat core ‘TP-2005’ have been carried out for the 0–130 ka interval. The results show that the TP basin is ideally positioned to receive tephra fall from both the Italian and Aegean Arc volcanic provinces. Two visible tephra layers, the Santorini Cape Riva/Y-2 (c. 22 ka) and the Campanian Ignimbrite (CI)/Y-5 (c. 39.8 ka) tephras, and six primary cryptotephra layers, namely the early Holocene E1 tephra from the Aeolian Islands (c. 8.3 ka), the Campanian Y-3 (c. 29 ka) and X-6 tephras (c. 109.5 ka), as well as counterpart tephras TM-18-1d (c. 40.4 ka), TM-23-11 (c. 92.4 ka) and TM-33-1a (c. 116.7 ka) from the Lago Grande di Monticchio sequence (southern Italy), were identified along with repeatedly redeposited Y-2 and CI tephra material. Bayesian modelling of the ages of seven of the primary tephra layers, 60 radiocarbon measurements and 20 palynological control points have been applied to markedly improve the chronology of the TP archive. This revised chronology constrains the age of tephra TM-18-1d to 40.90–41.66 cal ka BP (95.4% range). Several tephra layers identified in the TP record form important isochrons for correlating this archive with other terrestrial (e.g., Lago Grande di Monticchio, Sulmona Basin and Lake Ohrid) and marine (e.g., Adriatic Sea core PRAD 1-2 and Aegean Sea core LC21) palaeoclimate records in the Mediterranean region

Defining the Upper Nisyros Pumice (57.1 ± 1.5 ka) as new tephra isochrone for linking early MIS-3 palaeoenvironmental records in the Aegean-Black Sea gateway: New evidence from the Sea of Marmara

International audienceThe rhyolitic Upper Nisyros Pumice (UNP) from the Kos-Yali-Nisyros volcanic system has been detected as a cryptotephra layer in lacustrine sediments from the Sea of Marmara (SoM). A new independent age of the UNP eruption at 57.1 ± 1.5 cal ka BP has been interpolated using a combination of radiocarbon dating, tephrochronology and wiggle-matching of the SoM proxy record (Ca-curves) with Greenland oxygen isotope data, therewith confirming recently published radioisotopic dates of UNP land deposits. The UNP tephra in the SoM was identified by comparisons of the SoM tephra glass chemical dataset with published data of other marine tephra records from the Aegean Sea and the Megali Limni lacustrine sediment sequence (Lesvos Island). The stratigraphic position of the UNP tephra in these records verified its deposition in the SoM at the onset of MIS-3 and specifically at the termination of Greenland Interstadial GI-16. The new findings define the UNP tephra as a valuable time marker for the synchronisation of palaeoenvironmental data for this time period and help spurring the establishment of a robust tephrostratigraphical framework for the last ~70 kyr in the Aegean-Black Sea region

Fluorbritholite-(Nd), Ca2Nd3(SiO4)3F, a new and key mineral for neodymium sequestration in REE skarns

Fluorbritholite-(Nd), ideally Ca2Nd3(SiO4)3F, is an approved mineral (IMA 2023-001) and constitutes a new member of the britholite group of the apatite supergroup. It occurs in skarn from the Malmkärra iron mine, Norberg, Västmanland (one of the Bastnäs-type deposits in Sweden), associated with calcite, dolomite, magnetite, lizardite, talc, fluorite, baryte, scheelite, gadolinite-(Nd) and other REE minerals. Fluorbritholite-(Nd) forms anhedral and small grains, rarely up to 250 µm across. They are brownish pink, transparent with a vitreous to greasy luster. The mineral is brittle, with an uneven or subconchoidal fracture, and lacks a cleavage. In thin section, the mineral is nonpleochroic, uniaxial (-). Dcalc = 4.92(1) g·cm-3 and ncalc = 1.795. The empirical chemical formula from electron microprobe (WDS) point analyses is (Ca1.62Nd0.97Ce0.83Y0.52Sm0.30Gd0.23Pr0.17La0.16Dy0.11Er0.03Tb0.03Ho0.01Yb0.01)Σ4.99(Si2.92P0.08As0.01)Σ3.01O12.00[O0.48F0.26(OH)0.14Cl0.10Br0.02]Σ1.00. The crystal structure of fluorbritholite-(Nd) was refined from single-crystal X-ray diffraction data to R1= 0.043 for 704 unique reflections. It belongs to the hexagonal system, space group P63/m, with unit cell parameters a = 9.5994(3), c = 6.9892(4) Å, V = 557.76(5) Å3 for Z = 2. Fluorbritholite-(Nd) and other britholite-group minerals are a major sink for neodymium in REE-bearing skarns of Bastnäs type.

Detection of Rare Earth Elements (REEs) in mine waste applying destructive and spectral techniques: a chance to overcome the rising worldwide REEs demand?

he increasing demand of Rare Earth Elements (REE) in the industry and their economic relevance plays a crucial role in the mining exploration. In order to cover the worldwide demand unconventional deposits such as dumps and tailings from abandoned mines are being considered as a new source to recover REE bearing minerals. Purwadi et al. (2018) have investigated the concentration and visible and near-infrared reflectance spectroscopy of REEs-bearing tailings of a closed tin mine located on the Bangka Island (Indonesia) but detected no REEs bearing minerals due to their low abundance (<1wt.%). Our study investigates the sediments (quartz rich tailings) from this tin mine by means of Electron Microprobe (EMP). The measurements on 12 tailing samples have shown the occurrence of zircon ZrSiO4 and abundant REE bearing minerals such as monazite (Ce,La)PO4 , xenotime YPO4 , thorite (Th,U)SiO4, and uranite UO2. REEs bearing phases occur in quartz or at the grain boundaries, are approximately 5 to 50 μ large, and form relatively fresh (poorly altered) un-to subhedral grains providing suitable surfaces for EMP point analyses. Plotting the concentration of the REEs of monazite and xenotime in the chondrite normalized diagram they show the typical monazite decreasing and xenotime increasing pattern with no obvious anomaly. Chemically monazites are characterized by high thorium (up to 18% ThO - mainly as huttonite component) and very high yttrium and xenotime component (up to 3.5 wt. % Y2O3) indicating a high monazite formation temperature. More analyses including ICP-OES on selected samples are planned in the near future to investigate REE distribution in these type of deposits e.g. depleting and or enrichment triggered by fluids, weathering and alteration. The integration of spectral techniques and mineralogical-chemical investigations such as EMP and ICP-OES should play a crucial role in the future to characterize dumps, for the recovery of REEs and their signature in the deposits leading to a sustainable and economical extraction