Geology Today最新文献

Kimberlites, while relatively rare, are perhaps the most interesting of igneous rocks and have accordingly attracted attention disproportionate to their abundance. They are the source of most diamonds and bring us direct sampling of Earth’s mantle (otherwise only available indirectly by geophysical methods). They are confined to the ancient cratons of the continents: the oldest and thickest parts of the continental crust (where the geothermal gradient is low) and are now known to occur on all the continents. They were not formed in the earliest phases of Earth’s history. Emplaced explosively in carrot-shaped pipes, they are pyroclastic rocks close to the surface (often removed by erosion) but become hypabyssal (dykes and sills) at depth. Kimberlites belong to the ultramafic group of rocks with high MgO. They are consequently rich in olivine and lack feldspar. They are rich in volatiles, such as water and carbonate, and the above-mentioned mantle xenoliths and megacrysts, including eclogite, harzburgite, olivine, mica, zircon, diamond and others, as well as crustal xenoliths. Kimberlites are thus hybrid rocks and the nature of the parent magmas is difficult to define. Related rocks, which may contain diamonds, are lamproites and ultramafic lamprophyres. A recent article by Tony Waltham in Geology Today discussed kimberlites and especially their diamonds; here we concentrate on kimberlites themselves with lesser emphasis on other diamondiferous rocks.

With the transition to a low carbon future and increasing technological applications, the global demand for metals will continue to rise into the foreseeable future. However, primary ore deposits are finite, and to continue production, lower grade and more complex ore deposits need to be discovered, evaluated and exploited, with increasing exploration and production costs. Additionally, there are significant geopolitical constraints on global resources for some critical raw materials and metals, along with ethical constraints of ‘off-shoring’ minerals supply to areas of the world with poor records in terms of legal mineral production, human rights violations, health and safety, and the long-term environmental impact of mining. Whilst it is unlikely at present to be able to fully meet supply needs, one source of metals for the future is through recycling of both domestic and industrial waste. Modern waste streams such as end-of-life lithium-ion batteries and electrical waste commonly contain significantly more metals than primary ore deposits before processing. However, these waste materials are complex, and through two case studies in this article, we focus on how methods commonly used in modern mining and mineral processing can be used to assist the processing and recovery of metals from waste. Perhaps it is time to reclassify waste as valuable resources for the future.

The 1942 El Alamein battlefield exemplifies the decisive role of geological and geomorphological factors in modern warfare. Constrained between the Mediterranean littoral and the impassable Qattara Depression, the desert theatre imposed strategic immobility and shaped both defensive planning and tactical manoeuvre. Key landforms—dune ridges, aeolian sands, sabkhas and deir depressions—influenced fortification siting, troop disposition and operational viability. The Battle of Alam Halfa underscores how deep soft sands, compounded by a deceptive ‘going map’, critically hindered Rommel’s flanking attempt, already undermined by fuel shortages and Allied air dominance. Here, terrain functioned as a strategic agent.

About halfway between Interlaken and Bern, Thun is one of the latest sheets to appear in the 1:25 000 geological atlas of Switzerland planned series of 220 sheets. Thun adds to the recent publication of four geological maps extending along the river Aare and the Brienzersee up the Haaslital valley, in the headwaters of this tributary of the river Rhine and the longest river flowing entirely within Switzerland.

Ammonites were molluscs, now extinct, that abounded in Mesozoic seas. Their external shells are almost always the only parts of them that are preserved, and their soft-part anatomy and lifestyles remain largely unknown. The shells, however, can be preserved in various ways that shed light on the animals as living organisms, including their variation and evolution, possible colour patterning and the creatures that preyed upon them.

The biggest UK railway construction site since the nineteenth century has exposed a near-complete time slice through the entire Jurassic succession of central England. This is yielding a wealth of stratigraphical, palaeobiological and palaeoenvironmental data that is otherwise generally poorly exposed at the present day. Construction of the HS2 (High Speed 2) railway scheme is generating important exposures of these strata, affording significant geological recording, research and educational opportunities.

The Lower Jurassic Down Cliff Sand Member of the Dorset coast, southern England, is a rich source of marine invertebrate fossils. Among these are echinoderms and less common arthropods. Despite having multi-component skeletons that are prone to disarticulation, remains of some of these are remarkably complete. This article examines the circumstances that could have led to their death, burial and intact preservation.