| 1. |
- A. Marques, Ana F., et al.
(författare)
-
The Seven Sisters Hydrothermal System : First Record of Shallow Hybrid Mineralization Hosted in Mafic Volcaniclasts on the Arctic Mid-Ocean Ridge
- 2020
-
Ingår i: Minerals. - : MDPI AG. - 2075-163X.
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We document the discovery of an active, shallow, seafloor hydrothermal system (known as the Seven Sisters Vent Field) hosted in mafic volcaniclasts at a mid-ocean ridge setting. The vent field is located at the southern part of the Arctic mid-ocean ridge where it lies on top of a flat-topped volcano at ~130 m depth. Up to 200 deg C phase-separating fluids vent from summit depressions in the volcano, and from pinnacle-like edifices on top of large hydrothermal mounds. The hydrothermal mineralization at Seven Sisters manifests as a replacement of mafic volcaniclasts, as direct intraclast precipitation from the hydrothermal fluid, and as elemental sulfur deposition within orifices. Barite is ubiquitous, and is sequentially replaced by pyrite, which is the first sulfide to form, followed by Zn-Cu-Pb-Ag bearing sulfides, sulfosalts, and silica. The mineralized rocks at Seven Sisters contain highly anomalous concentrations of ‘epithermal suite’ elements such as Tl, As, Sb and Hg, with secondary alteration assemblages including silica and dickite. Vent fluids have a pH of ~5 and are Ba and metal depleted. Relatively high dissolved Si (~7.6 mmol/L Si) combined with low (0.2–0.4) Fe/Mn suggest high-temperature reactions at ~150 bar. A delta-13C value of -5.4 permil in CO2 dominated fluids denotes magmatic degassing from a relatively undegassed reservoir. Furthermore, low CH4 and H2 (<0.026 mmol/kg and <0.009 mmol/kg, respectively) and 3He/4He of ~8.3 R/Racorr support a MORB-like, sediment-free fluid signature from an upper mantle source. Sulfide and secondary alteration mineralogy, fluid and gas chemistry, as well as delta-34S and 87Sr/86Sr values in barite and pyrite indicate that mineralization at Seven Sisters is sustained by the input of magmatic fluids with minimal seawater contribution. 226Ra/Ba radiometric dating of the barite suggests that this hydrothermal system has been active for at least 4670 +/- 60 yr.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Bisang, Irene, et al.
(författare)
-
Immer weniger Ackermoose im Schweizer Mittelland
- 2021
-
Annan publikation (populärvet., debatt m.m.)abstract
- Ähnlich wie die Wildkräuter in Äckern sind auch die typischen, hoch-spezialisieren Ackermoose gefährdet und im Rückgang begriffen. Im Schweizer Mittelland sind ihre bevorzugten Lebensräume, bis in den Spätherbst unbearbeitete Getreidestoppelfelder, fast vollständig verschwunden. Biodiversitätsförderflächen (BFF) können dazu beitragen, ihren Rückgang zu stoppen, allerdings nur so lange nicht die dichte Vegetationsbedeckung und Streuauflagen in den älteren BFF die Ackermoose verdrängen. Entscheidend für den Erhalt der Ackermoose im Schweizer Kulturland ist deshalb die Förderung von kurzlebigen BFF und vor allem von Getreidestoppelfeldern, in denen die Bearbeitungszeitpunkte sorgfältig angepasst sind.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Cannon, P., et al.
(författare)
-
Revisions of British and Irish Lichens vol. 3 - Peltigerales: Collemataceae (including the genera Blennothallia, Callome, Collema, Enchylium, Epiphloea, Lathagrium, Leptogium, Pseudoleptogium, Rostania and Scytinium.
- 2020
-
Annan publikation (refereegranskat)abstract
- Revisions of British and Irish Lichens is a free-to-access serial publication under the auspices of the British Lichen Society, that charts changes in our understanding of the lichens and lichenicolous fungi of Great Britain and Ireland. Each volume will be devoted to a particular family (or group of families), and will include descriptions, keys, habitat and distribution data for all the species included. The maps are based on information from the BLS Lichen Database, that also includes data from the historical Mapping Scheme and the Lichen Ireland database. The choice of subject for each volume will depend on the extent of changes in classification for the families concerned, and the number of newly recognized species since previous treatments. To date, accounts of lichens from our region have been published in book form. However, the time taken to compile new printed editions of the entire lichen biota of Britain and Ireland is extensive, and many parts are out-of-date even as they are published. Issuing updates as a serial electronic publication means that important changes in understanding of our lichens can be made available with a shorter delay. The accounts may also be compiled at intervals into complete printed accounts, as new editions of the Lichens of Great Britain and Ireland.
|
|
| 8. |
- Drake, Henrik, 1979-, et al.
(författare)
-
Geochronology and Stable Isotope Analysis of Fracture-Fill and Karst Mineralization Reveal Sub-Surface Paleo-Fluid Flow and Microbial Activity of the COSC-1 Borehole, Scandinavian Caledonides
- 2020
-
Ingår i: Geosciences. - : MDPI AG. - 2076-3263.
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The deep biosphere hosted in fractured rocks within the upper continental crust is one of the least understood and studied ecological realms on Earth. Scarce knowledge of ancient life and paleo-fluid flow within this realm is owing to the lack of deep drilling into the crust. Here we apply microscale high spatial-resolution analytical techniques to fine-grained secondary minerals in a deep borehole (COSC-1) drilled into the Silurian-Devonian Scandinavian Caledonide mountain range in central Sweden. The aim is to detect and date signs of ancient microbial activity and low-temperature fluid circulation in micro-karsts (foliation-parallel dissolution cavities in the rock) and fractures at depth in the nappe system. Vein carbonates sampled at 684 to 2210 m show a decreased C isotope variability at depths below 1050 m; likely due to decreased influence of organic-C at great depth. Micro-karsts at 122–178 m depth feature at least two generations of secondary calcite and pyrite growth in the voids as shown by secondary ion mass spectrometry analytical transects within individual grains. The younger of these two precipitation phases shows 34S-depleted δ34Spyrite values (−19.8 ± 1.6‰ vs. Vienna-Canyon Diablo Troilite (V-CDT)) suggesting microbial sulfate reduction in situ. The calcite of this late phase can be distinguished from the older calcite by higher δ18Ocalcite values that correspond to precipitation from ambient meteoric water. The late stage calcite gave two separate laser ablation inductively coupled mass spectrometry-derived U-Pb ages (9.6 ± 1.3 Ma and 2.5 ± 0.2 Ma), marking a minimum age for widespread micro-karst formation within the nappe. Several stages of fluid flow and mineral precipitation followed karst formation; with related bacterial activity as late as the Neogene-Quaternary; in structures presently water conducting. The results show that our combined high spatial-resolution stable isotope and geochronology approach is suitable for characterizing paleo-fluid flow in micro-karst; in this case, of the crystalline crust comprising orogenic nappe units.
|
|
| 9. |
|
|
| 10. |
- Forshage, Mattias, et al.
(författare)
-
Signe Jenny Alfrida Ramberg : Entomolog, pionjär
- 2020
-
Annan publikation (populärvet., debatt m.m.)abstract
- Signe Ramberg var den första kvinnliga professionella entomologen i Sverige. Som extremt flitig preparator på Naturhistoriska riksmuseet under flera decennier spelade hon en imponerande stor och svåröverskådlig roll för uppbyggnaden av museets insektssamling.
|
|
