Studies on Schumann Resonance Phenomena and Some Recent Advancements

Geomagnetism and Aeronomy - Discrete spectra of frequencies at 8, 14, 20, 26, … Hz are generated by electromagnetic emission from lightning sources and can be regarded as excitation of AC...     

Solar Activity,Lightning and Climate

The physics of solar forcing of the climate and long term climate change is summarized, and the role of energetic charged particles (including cosmic rays) on cloud formation and their effect on climate is examined. It is considered that the cosmic ray-cloud cover hypothesis is not supported by presently available data and further investigations (during Forbush decreases and at other times) should be analyzed to further examine the hypothesis. Another player in climate is lightning through the production of NO_x; this greenhouse gas, water vapour in the troposphere (and stratosphere) and carbon dioxide influence the global temperature through different processes. The enhancement of aerosol concentrations and their distribution in the troposphere also affect the climate and may result in enhanced lightning activity. Finally, the roles of atmospheric conductivity on the electrical activity of thunderstorms and lightning discharges in relation to climate are discussed.     

Kinematics of large scale asymmetric folds and associated smaller scale brittle — Ductile structures in the proterozoic somnur formation, pranhita — Godavari Valley, South India

The development of structural elements and finite strain data are analysed to constrain kinematics of folds and faults at various scales within a Proterozoic fold-and-thrust belt in Pranhita-Godavari basin, south India. The first order structures in this belt are interpreted as large scale buckle folds above a subsurface decollement emphasizing the importance of detachment folding in thin skinned deformation of a sedimentary prism lying above a gneissic basement. That the folds have developed through fixed-hinge buckling is constrained by the nature of variation of mesoscopic fabric over large folds and finite strain data. Relatively low, irrotational flattening strain (X:Z-3.1-4.8, k<1) are associated with zones of near upright early mesoscopic folds and cleavage, whereas large flattening strain (X:Z-3.9-7.3, k<1) involving noncoaxiality are linked to domains of asymmetric, later inclined folds, faults and intense cleavage on the hanging wall of thrusts on the flanks of large folds. In the latter case, the bulk strain can be factorized to components of pure shear and simple shear with a maximum shearing strain of 3. The present work reiterates the importance of analysis of minor structures in conjunction with strain data to unravel the kinematic history of fold-and-thrust belts developed at shallow crustal level.     

Significance of rare hydrous alkaline melts in Hawaiian xenoliths

 Two types of melt pockets occur in Hawaiian mantle xenoliths: amphibole-bearing (AMP) and spinel-bearing (SMP). AMPs contain amphibole (kaersutite), olivine (Fo₉₂), clinopyroxene (with 7–11% Al₂O₃), vesicles and glass. SMPs contain olivine, clinopyroxene, spinel, glass, and vesicles. The glasses in SMPs (SiO₂=44–45%, 11–12% alkalis, La=90–110 ppm) and AMPs (SiO₂=49–54%, 6–8.5% alkalis, La=8–14 ppm) are distinct in color and composition. Both glasses are generally characterized by LREE-enriched (chondrite-normalized) patterns. Amphibole and clinopyroxene have gently convex upward-to-moderately LREE-enriched patterns. Mineral/glass trace element abundance ratio plots show a strong negative Ti anomaly and a gentle negative Zr anomaly for clinopyroxene/glass; whereas amphibole/glass patterns show a distinctive positive Ti spike. The amphibole/glass trace element ratios are similar to published megacryst/lava values. An earlier study showed that the Hawaiian spinel lherzolites (lithosphere) have largely been metasomatized during post-erosional Honolulu magmatic activity. REE abundances of SMP glasses (melts) overlap the REE abundances calculated for such metasomes. The occurrence of hydrous, alkaline, mafic melt pockets in Hawaiian upper mantle xenoliths implies that (1) such hydrous liquids are generated in the upper mantle, and (2) water plays a role in magmatic activity associated with the Hawaiian plume. Although we are uncertain about the source (plume, lithosphere, or asthenosphere) of this water, we speculate that such melts and other alkalic lavas erupted on Oahu and on the sea-floor over the Hawaiian arch were generated from a broad „wet“ rim of a radially layered Hawaiian plume, whose hot and „dry“ core supplied the shield-forming magmas. Received: 6 February 1995 / Accepted: 28 August 1995     

A rare composite xenolith from Salt Lake Crater,Oahu: high-pressure fractionation and implications for kimberlitic melts in the Hawaiian mantle

A composite xenolith of olivine-bearing garnet clinopyroxenite wall rock intruded by two spinels + garnet veins is described. Vein minerals exhibit textural evidence of a reaction relationship with the mineral phases in the wall rock. Wall rock clinopyroxene contains exsolved blebby garnet and very fine lamellar exsolution of orthopyroxene, indicating that this xenolith had undergone considerable subsolidus cooling. Garnet-clinopyroxene thermometry suggests that the xenolith last equilibrated in the mantle at a temperature of about 1,060 (ᆭ °C). The spinels in the veins are of two kinds: pleonaste (that occurs with vein garnet) and a high-Mg, high-Al titanomagnetite (MAT spinels). Intriguingly, the MAT spinels are chemically very similar to the spinels found as groundmass in kimberlites, are moderately subhedral to euhedral, have a weakly developed cumulate texture, and, at places, show a reaction relation with the pleonaste + garnet (cumulate?) assemblage in the vein. Based on petrographic, chemical, and phase equilibrium considerations, we propose the following evolutionary history of this composite xenolith. (1) In the first stage the olivine-bearing garnet clinopyroxenite formed as crystal extracts (cumulates) as a result of high pressure fractionation of an alkaline melt in the deepest levels of Hawaiian lithosphere/uppermost asthenosphere (100-110 km). (2) In the second stage, igneous veining (the melt composition of this vein is not precisely known but could be kimberlitic) occurs in the already existing wall rock resulting in the precipitation of pleonaste + garnet. A reaction relation between the igneous veins and the wall rock also characterizes this stage. (3) The last igneous episode in this xenolith is recorded by MAT spinels in the wall rock and their precipitation close to the previous pleonaste + garnet veins. The last igneous stage could well be due again to high pressure fractionation of a kimberlitic melt (the residual melt after precipitation of pleonaste + garnet). The time relationship between exsolution and the later igneous veining stages is not known. The MAT spinels are not a result of sub-solidus solvus processes as partial reaction (melt present) between the pleonaste + garnet (from the second igneous stage) and MAT spinel exists, pointing to the igneous nature of the MAT spinel. Based on striking similarity between the MAT spinels in our xenolith and those found as groundmass in kimberlites, we propose that the veining stages could well have been kimberlitic. Thus, even though kimberlitic melts are not seen on the Koolau shield, this particular xenolith clearly shows the existence of such melts at great depths beneath Hawaii. We also propose that the initial wall rock, which represents crystal extracts (even though it does not exhibit definitive cumulate texture) as a result of high-pressure fractionation of an alkaline melt and subsequent veining episodes, are of pre-Koolau age. This implies that the Koolau shield volcano may have had a pre-shield alkalic stage.     

Structural and Hydrogeological Controls on Hydrocarbon and Brine Migration into Drinking Water Aquifers in Southern New York

Environmental concerns regarding the potential for drinking water contamination in shallow aquifers have accompanied unconventional energy development in the northern Appalachian Basin. These activities have also raised several critical questions about the hydrogeological parameters that control the naturally occurring presence and migration of hydrocarbon gases in shallow aquifers within petroliferous basins. To interrogate these factors, we analyzed the noble gas, dissolved ion, and hydrocarbon gas (molecular and isotopic composition) geochemistry of 98 groundwater samples from south‐central New York. All samples were collected ?1km from unconventional drilling activities and sample locations were intentionally targeted based on their proximity to various types of documented fault systems. In agreement with studies from other petroliferous basins, our results show significant correlations between elevated levels of radiogenic [⁴He], thermogenic [CH₄], and dissolved ions (e.g., Cl, Br, Sr, Ba). In combination, our data suggest that faults have facilitated the transport of exogenous hydrocarbon‐rich brines from Devonian source rocks into overlying Upper Devonian aquifer lithologies over geologic time. These data conflict with previous reports, which conclude that hydrodynamic focusing regulates the occurrence of methane and salt in shallow aquifers and leads to elevated levels of these species in restricted flow zones within valley bottoms. Instead, our data suggest that faults in Paleozoic rocks play a fundamental role in gas and brine transport from depth, regulate the distribution of their occurrence in shallow aquifers, and influence the geochemistry of shallow groundwater in this petroliferous basin.