Stress Sensitivity of Seismic and Electric Rock Properties of the Upper Continental Crust at the KTB

2006 ◽  
pp. 1021-1029
Author(s):  
Axel Kaselow ◽  
Katharina Becker ◽  
Serge A. Shapiro
Keyword(s):  
Continental Crust ◽  
Stress Sensitivity ◽  
Rock Properties ◽  
Upper Continental Crust

Stress Sensitivity of Seismic and Electric Rock Properties of the Upper Continental Crust at the KTB

2006 ◽  
Vol 163 (5-6) ◽  
pp. 1021-1029
Author(s):  
Axel Kaselow ◽  
Katharina Becker ◽  
Serge A. Shapiro
Keyword(s):  
Continental Crust ◽  
Stress Sensitivity ◽  
Rock Properties ◽  
Upper Continental Crust

scholarly journals Paleofluids and Recent fluids in the upper continental crust: Results from the German Continental Deep Drilling Program (KTB)

1997 ◽  
Vol 102 (B8) ◽  
pp. 18233-18254 ◽  
Author(s):  
P. Möller ◽  
S. M. Weise ◽  
E. Althaus ◽  
W. Bach ◽  
H. J. Behr ◽  
...  
Keyword(s):  
Continental Crust ◽  
Deep Drilling ◽  
Upper Continental Crust ◽  
Continental Deep Drilling

scholarly journals The silicon isotope composition of the upper continental crust

2013 ◽  
Vol 109 ◽  
pp. 384-399 ◽  
Author(s):  
Paul S. Savage ◽  
R. Bastian Georg ◽  
Helen M. Williams ◽  
Alex N. Halliday
Keyword(s):  
Continental Crust ◽  
Isotope Composition ◽  
Silicon Isotope ◽  
Upper Continental Crust

scholarly journals The zirconium isotope composition of the mantle and upper continental crust through time

2021 ◽  
Author(s):  
Shengyu Tian ◽  
Frédéric Moynier ◽  
Edward Inglis ◽  
Roberta L. Rudnick ◽  
Fang Huang ◽  
...  
Keyword(s):  
Continental Crust ◽  
Isotope Composition ◽  
Upper Continental Crust

scholarly journals Preliminary Description of the Origin of a Sedimentary – Exhalative Ore Deposit, in Molango, Hidalgo Mexico

2018 ◽  
Author(s):  
Eduardo Cerecedo-Sáenz ◽  
Ventura Rodríguez-Lugo ◽  
Juan Hernández-Ávila ◽  
Demetrio Mendoza-Anaya ◽  
Ma. Isabel Reyes-Valderrama ◽  
...  
Keyword(s):  
Continental Crust ◽  
Rare Earths ◽  
Mineral Deposit ◽  
Base Metals ◽  
Sulfur Deficiency ◽  
Ore Deposit ◽  
Upper Continental Crust ◽  
Distribution Of Elements ◽  
Hydrothermal Remobilization ◽  
Preliminary Description

This work shows the preliminary description of the origin of a sedimentary - exhalative outcrop of Jurassic Lower Pliensbachian. The location of this deposit was achieved by applying an examination based in the identification of sedimentary transgressions of heterochronies ages and the identification of a Rift – type mega –structure. According with the methodology, it was carried out a study of the discordant relationships between two types of sediments: continental and marine. According the characterization, it was noted the existence of light rare earths, in values that show positive anomalies in comparison with the distribution of elements in upper continental crust according to the Clarke [1], reflecting so a felsic affinity of the mineral deposit. Also, positive anomalies of platinum and Pd, were determined with marginal contents of Au and Ag; and finally the base metals Zn, Pb and Cu were detected in low contents, which could be due to the presence of altered shale. According to the sedimentary lithology found, which was of siliciclastic type; to the exhalative roots observed during the fieldwork; the presence of quartz minerals such as biotite and muscovite; the presence of minerals of hydrothermal remobilization like chalcopyrite with some base metals, altered shale, as well as sulfur deficiency; this mineral reservoir could be defined as a SEDEX – type.

Lithium isotopic composition and concentration of the upper continental crust

2004 ◽  
Vol 68 (20) ◽  
pp. 4167-4178 ◽  
Author(s):  
F.-Z. Teng ◽  
W.F. McDonough ◽  
R.L. Rudnick ◽  
C. Dalpé ◽  
P.B. Tomascak ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Continental Crust ◽  
Upper Continental Crust

Metal Sources in the Proterozoic Vazante-Paracatu Sediment-Hosted Zn District, Brazil: Constraints from Pb Isotope Compositions of Meta-Siliciclastic Units

2021 ◽  
Author(s):  
Neil A Fernandes ◽  
Gema R. Olivo ◽  
Daniel Layton-Matthews ◽  
Alexandre Voinot ◽  
Donald Chipley ◽  
...  
Keyword(s):  
Continental Crust ◽  
Isotopic Signature ◽  
Pb Isotope ◽  
Metal Sources ◽  
Upper Continental Crust ◽  
Basement Rocks ◽  
Siliciclastic Rocks ◽  
Brasiliano Orogeny ◽  
Isotope System ◽  
Parallel Arrays

ABSTRACT Different types of sediment-hosted whole-rock Pb isotope (206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb) compositions were determined from phyllites, carbonaceous phyllites (>1% TOC), and meta-litharenites belonging to the Serra do Garrote Formation, which is part of the Proterozoic Vazante Group, Brazil. Results were integrated with lithogeochemistry in order to identify the Pb isotopic signature of Zn enrichment (up to 0.24 wt.% Zn) associated with meta-siliciclastic-hosted sulfide mineralization that formed prior to the Brasiliano Orogeny (850 to 550 Ma) in order to (1) understand the nature of siliciclastic sediment sources, (2) identify possible metal sources in pre-orogenic meta-siliciclastic-hosted Zn mineralization, and (3) evaluate the genetic links between the Zn enrichment in the relatively reduced phyllite package, and different styles of syn-orogenic Zn ± Pb mineralization (hypogene Zn-silicate and Zn-Pb sulfide) in overlying dolomitic carbonates throughout the Vazante-Paracatu Zn District, Brazil. The whole-rock 206Pb/204Pb and 207Pb/204Pb isotope ratios of meta-siliciclastic rocks plot as positively sloping, sub-parallel arrays with radiogenic, upper continental crust compositions, which could represent a detrital contribution from at least two upper continental crust sources. However, the 206Pb/204Pb versus 207Pb/204Pb isotope system does not distinguish between Zn-enriched samples and un-mineralized samples. In the whole-rock 206Pb/204Pb–208Pb/204Pb plot, Zn-enriched samples form a flat trend of lower 208Pb/204Pb values (38.3 to 39.5) compared to the Zn-poor ones that follow common upper crustal trends. Zinc-enriched samples have low whole-rock Th/U values (<4) and higher whole-rock U concentrations compared to unmineralized samples. These support the hypothesis that U (± Pb) was added by pre-orogenic metalliferous fluids, which were in turn derived from underlying Paleoproterozoic and Archean basement rocks. Due to U addition, the original whole-rock thorogenic and uranogenic Pb isotope systems were decoupled in mineralized samples. Pre-orogenic metalliferous fluids have similar present-day first-order characteristics, including: (1) relatively high U/Pb and (2) low Th/U values, when compared to galena in the major carbonate-hosted Zn ± Pb deposits (Vazante, Morro Agudo, Ambrosia, Fagundes) in the Vazante Group. These results support the hypothesis that Zn-rich layers and veins in mineralized carbonaceous phyllites could be linked to the same origins as carbonate-hosted mineral deposits throughout the Vazante Basin, but further data are warranted. We suggest that the tectonic evolution of the Vazante Basin saw multiple phases of Zn-rich mineralization over protracted time periods from around 1200 to 550 Ma.

Overcoming Hole Instability in Highly Deviated Wells in the Kafr El Sheikh Shale, Offshore Mediterranean, Egypt

2021 ◽  
Author(s):  
Yasser Kholaif ◽  
Mahmoud Elmaghraby ◽  
Annick Nago ◽  
Jean-Michel Embry ◽  
Pramit Basu ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Lower Bound ◽  
Real Time ◽  
Pore Pressure ◽  
Nile Delta ◽  
Stress Sensitivity ◽  
Rock Properties ◽  
Well Drilling ◽  
Geomechanical Monitoring ◽  
Deviated Wells

Abstract Drilling challenges in offshore Nile Delta have been largely documented in the literature. Operators are often confronted with drilling problems related to shale swelling, cavings, tight holes in combination with increased risks of lost circulation in some of the highly depleted formations. The Kafr El Sheikh shale in particular, has been linked to many instances of wellbore instability, due to its mineralogical composition (estimated to be mostly smectite, >70%). From offset well drilling experience, it could also be noticed that insufficient mud weight was often used to drill through the Kafr El Sheikh Shale, causing wellbore failure in shear due to lack of support of the wellbore wall. In the past, multiple mud weight designs have been implemented relying solely on pore pressure as lower bound of the mud window. With the increased use of geomechanics, it has been demonstrated that the lower bound should be taken as the maximum of the pore pressure and borehole collapse pressure, thus accounting for the effects of formation pressure, horizontal and vertical stresses, rock properties as well as wellbore trajectory. It has been proven that slight overpressure is often encountered halfway through the Kafr El Sheikh formation, which would typically result in slightly higher borehole collapse pressures. In the study fields, the operator expressed interest in drilling highly deviated wells (> 60-70 degrees). This raised concerns for increased drilling challenges, especially in the Kafr El Sheikh. A comprehensive and systematic risk assessment, design of a fit-for-purpose solution and its implementation during drilling took place in the fields of interest. Offset well data analytics from the subject fields supported a holistic evaluation of drilling risks associated with the Kafr El Sheikh, providing good understanding of stress sensitivity on deviation, azimuth and lithology. Upon building a robust geomechanical model, calibrated against offset well drilling experience, pre-drill mud weight and drilling practices recommendations were provided to optimize the drilling program. Near real-time geomechanical monitoring was implemented which helped to manage the model uncertainties. The implementation of a holistic risk assessment, including geomechanical recommendations and near real-time geomechanical monitoring, was effective to lead the drilling campaign successfully. As a result, three high angle wells (> 60-70 degrees) were drilled through the challenging Kafr El Sheikh formation without any hole instability. An integrated risk assessment of hole instability, managed in stages (pre-drill and during drilling), has helped to understand and simulate the behaviors of the formation. Proactive decisions have established a controlled drilling environment for successful operations.

Evidence for contemporaneous Deccan volcanic aerosol deposition preceding the K-Pg boundary at El Kef, Tunisia

2021 ◽  
Author(s):  
Steffanie Sillitoe-Kukas ◽  
Munir Humayun ◽  
Thierry Adatte ◽  
Gerta Keller
Keyword(s):  
Continental Crust ◽  
Aerosol Deposition ◽  
Emission Rates ◽  
Volcanic Aerosol ◽  
Deccan Volcanism ◽  
Volatile Element ◽  
Asteroid Impact ◽  
Upper Continental Crust ◽  
El Kef ◽  
Volcanic Aerosols

<p>The cause of the Cretaceous-Paleogene extinction remains debated between an asteroid impact and volcanism. Precise geochronology showed that the extinction coincided with a voluminous phase (Poladpur eruption) of Deccan volcanism (Schoene et al., 2019). Paleontological evidence indicates that microfossil diversity declined about 300,000 years before the K-Pg boundary, synchronous with the onset of Deccan volcanism (Keller et al. 2009). High concentrations of Ir in the K-Pg boundary supported the asteroid hypothesis but recent work indicates that siderophile accumulation at the K-Pg in El Kef is secondary (Humayun et al., this conf.). Here, we critically examine existing element data for the K-Pg boundary and examine new results at the El Kef site, Tunisia, for volcanogenic volatile element accumulation associated with the contemporaneous Deccan eruptions. In this study, we analyzed 60 elements by laser ablation ICP-MS in search of these volcanic aerosol enrichments in the K-Pg sediments at El Kef, Tunisia. A study of siderophile element distribution at global K-Pg sites found that the Ru/Ir ratio is sub-chondritic. Mixing of upper continental crust (Ru/Ir> CI) with a chondritic impactor fails to explain this trend. Volcanic aerosol emissions for Ir are well known but there is less data available for Ru. Relative emission rates of Ru were found to be lower than those of Ir for the Kudryavy volcano (Yudovskaya et al., 2008), so a possible explanation of the sub-chondritic Ru/Ir ratio observed in global K-Pg sites involves deposition of volcanic aerosols in sediments. We also modeled the effect of adding volcanic aerosols to sediments approximated compositionally as upper continental crust (UCC) to find that Re, Cd, Os and Ir are the first elements to become enriched in sediments by volcanogenic aerosol deposition. Sediments from El Kef below the K-Pg boundary are enriched in both Re and Cd. On a plot of Cd vs. Re, the K-Pg sediment from El Kef falls on a mixing line between volcanic aerosol (Erta Ale volcano) and UCC. Sediment at 3 cm above the K-Pg boundary has little enrichment of either Cd or Re, interpreted here to indicate that this sediment was deposited in the interlude between the Poladpur and the Ambenali eruption phases of the Deccan. The availability of chemical proxies of volcanogenic aerosol deposition in sediments enables direct correlation between fossil evidence and the contemporaneous intensity of volcanic outgassing, the likely destroyer of life by the Deccan eruptions (Keller et al., 2020).</p>

Atmospheric dispersed sedimentary matter over the Barents sea

2021 ◽  
pp. 127-142
Author(s):  
V.P. Shevchenko ◽  
◽  
L.P. Golobokova ◽  
S.M. Sakerin ◽  
A.P. Lisitzin ◽  
...  
Keyword(s):  
Continental Crust ◽  
Barents Sea ◽  
Chemical Elements ◽  
Ionic Composition ◽  
Anthropogenic Pollution ◽  
Insoluble Fraction ◽  
The Arctic ◽  
Noticeable Effect ◽  
The Barents Sea ◽  
Upper Continental Crust

The concentration and composition of aerosols in the atmosphere over the Barents Sea were studied. Earlier, the contribution of aerosols to the formation of the Arctic environment was underestimated. Our data indicated a noticeable effect of continental aerosol on the atmosphere of the Barents Sea. The relationship of the black carbon concentration and the type of air masses has been established. Its concentration increases hundreds of times in the atmosphere of the sea when continental air is removed. The ionic composition and the content of chemical elements in the insoluble fraction of aerosols of the air over the Barents Sea were studied. The content of most chemical elements (Na, Al, K, Ca, Sc, Fe, Co, Rb, Zr, Cs, Ba, REE, Hf, Ta, Th, U) in the insoluble fraction of aerosols was below the average values for the upper continental crust. The content of Cr, Cu, Zn, As, Se, Br, Ag, Sb, Au, Pb is significantly higher than their average for the upper continental crust, due to the influence of the anthroposphere. Probable sources of anthropogenic pollution of aerosols in the Arctic are discussed.

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