Extensional Veins and Pb-Zn Mineralisation in Basement Rocks: The Role of Penetration of Formation Brines

2002 ◽  
pp. 189-205 ◽  
Author(s):  
S. A. Gleeson ◽  
B. W. D. Yardley
Keyword(s):  
Basement Rocks

scholarly journals The role of geological structures on groundwater occurrence and flow in crystalline basement aquifers: a status review

2018 ◽  
Vol 11 (1) ◽  
pp. 155-164
Author(s):  
M.A. Idris ◽  
M.L. Garba ◽  
S.A. Kasim ◽  
I.M. Madabo ◽  
K.A. Dandago
Keyword(s):  
Hydrological Cycle ◽  
Crystalline Basement ◽  
Geological Structures ◽  
Secondary Porosity ◽  
Groundwater Movement ◽  
Remote Sensing Technique ◽  
Basement Rocks ◽  
Groundwater Occurrence ◽  
Basement Aquifers

The paper is review on the role of geological structures on groundwater occurrence and flow in Crystalline Basement aquifers. The aim was to study the existing available literatures in order to evaluate structural/lineaments (faults, joints/fractures, folds, shear zone etc.) their influences and controls of groundwater occurrence and flow of bedrock of crystalline rocks of igneous and/or metamorphic origin. Groundwater in the basement aquifers resides/occurs within the weathered overburden and fractured bedrocks which originate from rainfall through the process of hydrological cycle. Remote sensing technique uses satellite imagery or aerial photograph to identify linear features on the ground and attempts to relate these lines to geologic structures capable of transmitting and storing large quantities of groundwater. Faults, joints/fractures and folds act as conduit and make rocks excellent aquifers. These features also, served as channels for groundwater movement which may results to an increased in secondary porosity, permeability and therefore, can results as a groundwater prospective/promising zones in crystalline basement rocks. Keywords: Basement Terrain, Groundwater, Lineament, Movement, Occurrence

The role of geology and climate in soil nutrient variability - potential drivers for large ungulate migrations in the Serengeti ecosystem (Northern Tanzania, East Africa)

2020 ◽  
Author(s):  
Eileen Eckmeier ◽  
Simon Kübler ◽  
Akida Meya ◽  
Stephen Mathai Rucina
Keyword(s):  
Volcanic Eruptions ◽  
East African ◽  
Near Surface ◽  
Serengeti Ecosystem ◽  
Geological Processes ◽  
Basement Rocks ◽  
Nutrient Variability ◽  
Archean Basement

<p>The East African Serengeti ecosystem hosts a great range of mammals and one of the world’s largest seasonal ungulate movements, with over 1.3 wildebeest and several hundreds of thousands of zebras and antelopes migrating through the region in a regular pattern. While climatic and biological drivers for this migration have been studied in great detail, the role of rock chemistry, weathering and resulting soil diversity as a source for nutrient provision has so far been largely neglected and needs detailed and systematic study.</p><p>Geological processes provide important controls on long-term ecosystem dynamics. Volcanic eruptions, earthquakes, and rock weathering influence soil edaphic properties, which represent the ability of soils to provide vital plant-available nutrients, which therefore control grazing patterns of herbivores, particularly during birthing and lactating seasons. Studying the geological role in providing and distributing essential nutrients is critical to understand long-term drivers and stability of animal migrations in dynamic ecosystems. We have carried out a field reconnaissance study in the Serengeti National Park, with the aim to study variations in nutrient variability in soils and vegetation in relation to the chemical composition of soil parent material, i.e. volcanic or metamorphic rocks and sediments derived from those rock units, and under consideration of climatic variations. First results show that the Serengeti ecosystem can be subdivided into three geo-edaphic subregions that correlate with seasonal wildebeest grazing habitats.</p><p>(1) The southeastern Serengeti (wet-season grazing), is characterized by soils developed on volcanic ash derived from recent eruptions of the Ol Doinjo Lengai carbonatite volcano. Here, we have identified deeper organic-rich soils with andic and vitric properties and varying amounts of carbonate concretions or near-surface calcrete horizons. High Na, K, and Ca levels of volcanic ashes suggest high levels of those elements in soils and vegetation in this region, also because the precipitation is lowest in this area.</p><p>(2) In the central Serengeti (short-term transitional grazing), soils develop on Archean basement rocks including granitic gneisses, phyllites and banded iron formations. Geochemical signatures of these rock types suggest that soils in this region have lower levels in Ca, Mg, and plant available P, compared to the SE Serengeti, which is supported by the transitional nature of this grazing habitat.</p><p>(3) Soils in the Northern Serengeti (dry-season grazing) develop on a diverse patchwork of Archean basement rocks as well as basaltic lavas and thick fluvial deposits. North of Mara river, the Insuria fault – a large normal fault of the East African Rift  - creates a wide sedimentary basin dominated by soils developed on basaltic sediments. Here, higher precipitation leads to stronger weathering and leaching of nutrient elements.</p><p>Our preliminary results suggests that geochemical variations together with continuous (syngenetic) pedogenesis through active volcanism or tectonic faulting and related fault scarp erosion created regions of high edaphic quality in the north and southeast of the Serengeti ecosystem, and that the patchy nature of soil edaphics is important to understand the underlying drivers of large scale migration of grazing animals in this region. </p>

scholarly journals Rock fracturing by subglacial hydraulic jacking in basement rocks, eastern Sweden: the role of beam failure

GFF ◽  
2021 ◽  
pp. 1-16
Author(s):  
Maarten Krabbendam ◽  
Romesh Palamakumbura ◽  
Christian Arnhardt ◽  
Adrian Hall
Keyword(s):  
Rock Fracturing ◽  
Basement Rocks ◽  
Hydraulic Jacking

The chemical evolution from older (323–318 Ma) towards younger highly evolved tin granites (315–314 Ma)—sources and metal enrichment in Variscan granites of the Western Erzgebirge (Central European Variscides, Germany)

2020 ◽  
Author(s):  
Marion Tichomirowa ◽  
Axel Gerdes ◽  
Manuel Lapp ◽  
Dietmar Leonhardt ◽  
Martin Whitehouse
Keyword(s):  
Granulite Facies ◽  
Source Rocks ◽  
Metamorphic Rocks ◽  
Control Factor ◽  
Basement Rocks ◽  
Ore Bodies ◽  
O Isotopes ◽  
Variscan Granites ◽  
Highly Evolved

<p>The sources and critical enrichment processes for granite related tin ores are still not well understood. The Erzgebirge represents one of the classical regions for tin mineralization. We investigated the four largest plutons from the Western Erzgebirge (Germany) for the geochemistry of bulk rocks and autocrystic zircons and relate this information to their intrusion ages. The source rocks of the Variscan granites were identified as high-grade metamorphic rocks based on the comparison of Hf-O isotope data on zircons, the abundance of xenocrystic zircon ages as well as Nd and Hf model ages. Among these rocks, restite is the most likely candidate for later Variscan melts.</p><p>In contrast to previously published suggestions (Romer and Kroner, 2015; Wolf et al., 2018), we can exclude a substantial role of intense sedimentary weathering as an important control factor for later Sn and W enrichment in granite related ores of the Western Erzgebirge due to the remarkable homogeneous Hf and low O isotopes in granitic zircons that are extremely distinct to all pre-Devonian basement rocks of Saxothuringia. We document a source enrichment from meta-sedimentary rocks (575 Ma) towards metamorphic rocks (340 Ma) were restites from granulite-facies melts are enriched 6–7 times in Sn compared to UCC (upper continental crust). These rocks are also enriched in K, but depleted in Na and Ca, contain abundant muscovite, and are fertile for later melting. Further enrichment of Sn and W occurred during multiple melt production of the older igneous granites (323–318 Ma) leading finally to a general enrichment of Sn (15 times compared to UCC) in the tin granites (315-314 Ma). Multiple melt production did not lead to a very strong enrichment of ore metals in the granites but is probably very important for a general enrichment of Sn and W in the thick granite-rich crust of the Erzgebirge. Efficient leaching by hydrothermal fluids led to a very strong enrichment (up to several orders) of Sn and W in the greisen ore bodies.</p><p> </p><p>References:</p><p>Romer, R.L.; Kroner, U. Sediment and weathering control on the distribution of Paleozoic magmatic tin-tungsten mineralization. Mineral. Depos. 2015, 50, 327–338, doi:10.1007/s00126-014-0540-5.</p><p>Wolf, M.; Romer, R.L.; Franz, L.; Lopez-Moro, F.J. Tin in granitic melts: The role of melting temperature and protolith composition. Lithos 2018, 310–311, 20–30.</p>

scholarly journals Geochemical characteristics of Precambrian Basement rocks from southeastern Nigeria: an approach to their petrogenesis and tectonic setting.

2020 ◽  
Vol 18 ◽  
pp. 1-13
Author(s):  
CHINEDU UDUMA IBE
Keyword(s):  
Partial Melting ◽  
Tectonic Setting ◽  
Southeastern Nigeria ◽  
Eu Anomaly ◽  
Basement Rocks ◽  
Geochemical Study ◽  
Tectonic Significance ◽  
Granitic Intrusions ◽  
Ree Patterns

Trace and Rare-Earth element geochemical study of twenty samples of migmatitic banded gneisses, garnet biotite schists, dolerites, granites and rhyolites was carried out in a bid to determine their petrogenetic and tectonic significance in the evolution of the southeastern Basement complex of Nigeria. The data shows that partial melting (crustal anatexis) of migmatitic gneisses and schists played a significant role in the evolution of the granitic intrusions. This is supported by the high incompatible (Rb/Sr = 0.16 to 1.31 and Ba/Sr = 0.75 to 6.21) elements ratio in the granitic intrusions than that of the migmatitic gneisses and schists (Rb/Sr, 0.051 to 0.824; Ba/Sr, 0.7 to 5). High ratios of Ba/Sr and Rb/Sr and lesser values of Ba/Rb ratios in some granitic intrusions than in others suggests increasing fractionation during the anatexis. The role of partial melting is also evident in the smooth REE patterns shown by most of these rocks and the negative Eu anomaly as indicated by the values of Eu/Eu* (0.097 to 0.7). LREE enrichment is evident in the high values of Ce/YbN (12.08-174.5), La/YbN (15.2-228.4) and La/SmN (2.6-7.2) in the granitic intrusions. Tectonic discrimination diagrams of the rocks indicate that the basement rocks were most probably formed in a post-collision orogenic setting while the dolerite and the rhyolite were formed in within-plate anorogenic setting.

scholarly journals Литогенный фактор в формировании и распространении донных биоценозов (Апшеронский архипелаг, Каспийское море)

2020 ◽  
Vol 12 (3) ◽  
pp. 61
Author(s):  
К.М. Петров
Keyword(s):  
Caspian Sea ◽  
The Caspian Sea ◽  
Leading Role ◽  
Basement Rocks ◽  
Sea Bottom

The results of decades of comprehensive investigations of the undersea grounds of the Absheron Archipelago (the Caspian Sea), including landscape and bionomic zoning, which started in 1960ies, are overviewed. The five main types of undersea grounds and associated biocenoses are characterized with special attention to bivalve tanathocenoses associated with naked basement rocks. Based on these analyses, the leading role of geologic and geomorphologic structure of sea bottom in the development and distribution of natural complexes and biocenoses of sea bottom is suggested.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor
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