Elemental and isotopic tracing of mineral infillings from various microstructures of a fault system into fine-grained sediments: which interacting fluids?

2022 ◽  
Author(s):  
Norbert Clauer ◽  
Isabelle Techer ◽  
Christophe Nussbaum
Keyword(s):  
Fault System ◽  
Fine Grained ◽  
Isotopic Tracing

scholarly journals Hydrothermal mineral assemblages of calcite and dolomite–analcime–pyrite in Permian lacustrine Lucaogou mudstones, eastern Junggar Basin, Northwest China

2020 ◽  
Author(s):  
Hong Li ◽  
Yiqun Liu ◽  
Kang Yang ◽  
Yongjie Liu ◽  
Yuanzhe Niu
Keyword(s):  
Lake Water ◽  
Hydrothermal Fluid ◽  
Junggar Basin ◽  
Northwest China ◽  
Fault System ◽  
Rock Interaction ◽  
Continental Extension ◽  
Fine Grained ◽  
Mineral Assemblages ◽  
Hydrothermal Mineral

AbstractThe eastern Junggar Basin, controlled by continental extension (rift), was deposited by lacustrine dominated sediments during middle Permian Lucaogou period. An unusual porphyritic-like texture was observed in Lucaogou/Pingdiquan dark fine-grained organic-rich sediments in two sub-tectonic units in the basin. The “phenocrysts” are composed of two types of mineral assemblages. The first is a coarse euhedral calcite assemblage in the Jimusar Sag, and the second consists of dolomite, analcime, and pyrite in the Shishugou Sag. The lithological and mineralogical features indicate a hydrothermal origin for these phenocryst-like minerals. The chondrite-normalized rare earth element patterns show flat or positive Ce anomalies and negative Eu anomalies, which reflect a suboxic to anoxic, off-axis site from the center of the fault system, where the temperature of the hydrothermal fluid might be less than 250 °C. The high ratios of BaN/LaN at 1.6–65.5, strongly positive Sr anomalies at Sr/Sr* = 5.54–39.9, and relatively low 87Sr/86Sr isotopes at 0.705002–0.705776 in the coarse calcite suggest an origin of mixed sources of lake water, underlying biogenetic sediments, and deep magmatic water. However, the low 87Sr/ 86Sr ratios of 0.705321–0.705968 in the dolomite and δ34SV-CDT of 10.8‰–12.3‰ in the pyrite indicate that water–underlying-rock interaction and the abiotic thermochemical sulfate reduction of lake water or organic matter might have participated together resulting in the precipitation of the dolomite–analcime–pyrite assemblages in the Shishugou Sag.

scholarly journals Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

Solid Earth ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 1099-1121 ◽  
Author(s):  
Károly Hidas ◽  
Carlos J. Garrido ◽  
Guillermo Booth-Rea ◽  
Claudio Marchesi ◽  
Jean-Louis Bodinier ◽  
...  
Keyword(s):  
Grain Size ◽  
Lithospheric Mantle ◽  
Volcanic Field ◽  
Mantle Xenoliths ◽  
Coarse Grained ◽  
Fault System ◽  
Mantle Flow ◽  
Second Phase ◽  
Fine Grained ◽  
Wide Range

Abstract. Subduction-transform edge propagator (STEP) faults are the locus of continual lithospheric tearing at slab edges, resulting in sharp changes in the lithospheric and crustal thickness and triggering lateral and/or near-vertical mantle flow. However, the mechanisms at the lithospheric mantle scale are still poorly understood. Here, we present the microstructural study of olivine-rich lherzolite, harzburgite and wehrlite mantle xenoliths from the Oran volcanic field (Tell Atlas, northwest Algeria). This alkali volcanic field occurs along a major STEP fault responsible for the Miocene westward slab retreat in the westernmost Mediterranean. Mantle xenoliths provide a unique opportunity to investigate the microstructures in the mantle section of a STEP fault system. The microstructures of mantle xenoliths show a variable grain size ranging from coarse granular to fine-grained equigranular textures uncorrelated with lithology. The major element composition of the mantle peridotites provides temperature estimates in a wide range (790–1165 ∘C) but in general, the coarse-grained and fine-grained peridotites suggest deeper and shallower provenance depth, respectively. Olivine grain size in the fine-grained peridotites depends on the size and volume fraction of the pyroxene grains, which is consistent with pinning of olivine grain growth by pyroxenes as second-phase particles. In the coarse-grained peridotites, well-developed olivine crystal-preferred orientation (CPO) is characterized by orthorhombic and [100]-fiber symmetries, and orthopyroxene has a coherent CPO with that of olivine, suggesting their coeval deformation by dislocation creep at high temperature. In the fine-grained microstructures, along with the weakening of the fabric strength, olivine CPO symmetry exhibits a shift towards [010] fiber and the [010] and [001] axes of orthopyroxene are generally distributed subparallel to those of olivine. These data are consistent with deformation of olivine in the presence of low amounts of melts and the precipitation of orthopyroxenes from a melt phase. The bulk CPO of clinopyroxene mimics that of orthopyroxene via a topotaxial relationship of the two pyroxenes. This observation points to a melt-related origin of most clinopyroxenes in the Oran mantle xenoliths. The textural and geochemical record of the peridotites are consistent with interaction of a refractory harzburgite protolith with a high-Mg no. melt at depth (resulting in the formation of coarse-grained clinopyroxene-rich lherzolite and wehrlite) and with a low-Mg no. evolved melt in the shallow subcontinental lithospheric mantle (forming fine-grained harzburgite). We propose that pervasive melt–peridotite reaction – promoted by lateral and/or near-vertical mantle flow associated with lithospheric tearing – resulted in the synkinematic crystallization of secondary lherzolite and wehrlite and had a key effect on grain size reduction during the operation of the Tell–Rif STEP fault. Melt–rock reaction and secondary formation of lherzolite and wehrlite may be widespread in other STEP fault systems worldwide.

Geotechnical engineering significance of Great Plains polygonal fault system

2017 ◽  
Vol 54 (8) ◽  
pp. 1089-1103
Author(s):  
Andy St-Onge
Keyword(s):  
Great Plains ◽  
Upper Cretaceous ◽  
Geotechnical Engineering ◽  
Three Dimensional ◽  
Fault System ◽  
Niobrara Formation ◽  
Well Control ◽  
Fine Grained ◽  
Engineering Significance ◽  
Polygonal Fault

An extensive polygonal fault system (PFS) within fine-grained Upper Cretaceous sediments beneath the Great Plains of North America has implications for geotechnical engineering. Geological well control, outcrop, and three-dimensional seismic data from southeast Saskatchewan exemplify the fault characteristics typically observed within the PFS. The deepest faults are sparse, offset a seismic reflection identified from the Niobrara Formation Govenlock member, and have vertical offsets <2 m. The deformation increases in fault density and vertical offset at shallower depths, reaching 6 faults/km2 with up to 30 m of vertical offset. Upper Cretaceous strata throughout the Great Plains area are at or near outcrop, and the extensive PFS faulting and weathering have weakened the rock. This faulting and weakness have been observed and attributed to other factors such as glacial erosion, overconsolidation, swelling bentonite beds, or landslides from toe erosion at topographic slopes. The PFS faulting should be recognized as an extensive process to be considered when undertaking geotechnical analysis on the Great Plains where underlying Upper Cretaceous rocks exist. Engineering implications include road cuts, dam impoundments, building foundations, and natural slumping.

Geophysical and Geological investigations of a major Miocene fault system within the city of Vienna: evidence for active tectonics

2020 ◽  
Author(s):  
Bernhard Salcher ◽  
Jan-Christoph Otto ◽  
Stephanie Neuhuber ◽  
Christopher Lüthgens ◽  
Sabine Grupe ◽  
...  
Keyword(s):  
Fault Zone ◽  
Marine Sediments ◽  
Age Dating ◽  
Coarse Grained ◽  
Fault System ◽  
High Resistivity ◽  
Vienna Basin ◽  
Fine Grained ◽  
Aeolian Deposits ◽  
The City

&lt;p&gt;We present investigations of a major Miocene fault system crossing the city of Vienna by using sedimentological, geophysical, remote sensing and numerical age dating methods. The fault zone is located at the western edge of the Vienna Basin, a c. 55 km wide and c. 200 km long rhomb-shaped pull-apart basin, separating the mountain ranges of the Alps and Carpathians. At its western edge a major sidewall fault, the Leopoldsdorf Fault System&amp;#160; vertically offsets alpine units by up to 5 km. In this study, we focus on Pleistocene fluvial sediments of the Danube deposited along this fault zone. Distribution and facies provide suitable conditions to speculate on Quaternary fault activity. Fluvial gravels rest on top of fine-grained, marine sediments of the Miocene. Quaternary uplift preserved these sediments in the form of terraces that were extensively covered by Pleistocene aeolian deposits (i.e. loess). Later, solifluction affected those fine-grained sediments and obliterated the terrace steps resulting in a relative homogenously inclined top as well as a flat accumulation zone at the toe of the slope. Age brackets of Quaternary deposits are provided from redeposited quartz gravels using cosmogenically produced &lt;sup&gt;26&lt;/sup&gt;Al and &lt;sup&gt;10&lt;/sup&gt;Be as well as luminescence ages of the loess-like cover sediments.&lt;/p&gt;&lt;p&gt;The high resistivity contrast of the coarse-grained sediments to the underlying fine-grained marine sediments and the overlying loess deposits provided excellent conditions to infer the geometry of the fluvial deposits. Accordingly, we used electrical resistivity tomography and data derived from driller&amp;#8217;s lithologic logs to constrain possible vertical offset of terraces. Possible surface ruptures were discussed by utilizing data from LiDAR-based high-resolution digital elevation models.&lt;/p&gt;

scholarly journals Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

2019 ◽  
Author(s):  
Károly Hidas ◽  
Carlos J. Garrido ◽  
Guillermo Booth-Rea ◽  
Claudio Marchesi ◽  
Jean-Louis Bodinier ◽  
...  
Keyword(s):  
Grain Size ◽  
Lithospheric Mantle ◽  
Volcanic Field ◽  
Mantle Xenoliths ◽  
Coarse Grained ◽  
Fault System ◽  
Mantle Flow ◽  
Second Phase ◽  
Fine Grained ◽  
Wide Range

Abstract. Subduction-Transform Edge Propagator (STEP) faults are the locus of continual lithospheric tearing at slab edges, resulting in sharp changes in the lithospheric and crustal thickness and triggering lateral and/or near-vertical mantle flow. However, the mechanisms at the lithospheric mantle scale are still poorly understood. Here, we present the microstructural study of olivine-rich lherzolite, harzburgite and wehrlite mantle xenoliths from the Oran volcanic field (Tell Atlas, NW Algeria). This alkali volcanic field occurs along a major STEP fault responsible for the Miocene westward slab retreat in the westernmost Mediterranean. Mantle xenoliths provide a unique opportunity to investigate the microstructures in the mantle section of a STEP fault system. The microstructures of mantle xenoliths show a variable grain size ranging from coarse granular to fine-grained equigranular textures uncorrelated with modal variations. The major element composition of the mantle peridotites provides temperature estimates in a wide range (790–1165 °C) but in general, the coarse-grained and fine-grained peridotites suggest deeper and shallower provenance depth, respectively. Olivine grain size in the fine-grained peridotites depends on the size and volume fraction of the pyroxene grains, which is consistent with pinning of olivine grain growth by pyroxenes as second phase particles. In the coarse-grained peridotites, well-developed olivine crystal preferred orientation (CPO) is characterized by orthorhombic and [100]-fiber symmetries, and orthopyroxene has a coherent CPO with that of olivine, suggesting their coeval deformation by dislocation creep at high-temperature. In the fine-grained microstructures, along with the weakening of the fabric strength, olivine CPO symmetry exhibits a shift towards [010]-fiber and the [010]- and [001]-axes of orthopyroxene are generally distributed subparallel to those of olivine. These data are consistent with deformation of olivine in the presence of low amounts of melts and the precipitation of orthopyroxenes from a melt phase. The bulk CPO of clinopyroxene mimics that of orthopyroxene via a topotaxial relationship of the two pyroxenes. This observation points to a melt-related origin of most clinopyroxenes in the Oran mantle xenoliths. The textural and geochemical record of the peridotites are consistent with interaction of a refractory harzburgite protolith with a high-Mg# melt at depth (resulting in the formation of coarse-grained clinopyroxene-rich lherzolite and wehrlite), and with a low-Mg# evolved melt in the shallow subcontinental lithospheric mantle (forming fine-grained harzburgite). We propose that pervasive melt-peridotite reaction – promoted by lateral and/or near-vertical mantle flow associated with lithospheric tearing – resulted in the synkinematic crystallization of secondary lherzolite and wehrlite and played a key effect on grain size reduction during the operation of the Rif-Tell STEP fault. Melt-rock reaction and secondary formation of lherzolite and wehrlite may be widespread in other STEP fault systems worldwide.

Recognition of an early Holocene polygonal fault system in Lake Superior: Implications for the compaction of fine-grained sediments

Geology ◽  
2004 ◽  
Vol 32 (3) ◽  
pp. 253 ◽  
Author(s):  
Joseph Cartwright ◽  
Nigel Wattrus ◽  
Deborah Rausch ◽  
Alastair Bolton
Keyword(s):  
Lake Superior ◽  
Early Holocene ◽  
Fault System ◽  
Fine Grained ◽  
Polygonal Fault

Mechanical stratigraphy and layer-bound normal faulting in the Upper Cretaceous Niobrara Formation, Wattenberg Field, Colorado

2020 ◽  
Vol 57 (2) ◽  
pp. 67-93
Author(s):  
Kyle Bracken
Keyword(s):  
Upper Cretaceous ◽  
Fault System ◽  
Normal Faults ◽  
Valuable Insight ◽  
Niobrara Formation ◽  
Borehole Data ◽  
Fine Grained ◽  
Mechanical Stratigraphy ◽  
Pass Through ◽  
Dip Angle

Layer-bound normal faults are pervasive within the very fine-grained rocks of the Upper Cretaceous Niobrara and Carlile formations in the Denver Basin. 3-D seismic and well log interpretation reveal a complex, segmented fault system that is divided into two discrete tiers: an upper tier located in the Pierre Shale, and a lower tier located in the Niobrara Formation. 3-D fault throw analysis shows maximum throw near the top of the Niobrara Formation with steep, asymmetrical throw gradient down section in the lower Niobrara and Carlile formations. Faults are laterally well-connected in the upper Niobrara Formation and commonly form linear arrays of linked graben systems. In contrast, faults deeper in the stratigraphic section that offset the Carlile and Greenhorn formations are more segmented and commonly form half grabens (as opposed to full, fault-bound grabens). In cross-section, fault planes measured from seismic have a general dip of 45°. However, close inspection reveals that faults consistently change dip angle as they pass through the lower Niobrara Formation, refracting from ~55° to ~35° through the Niobrara C Marl, then back up to ~50° in the Carlile and Greenhorn formations. The fault dip refraction produces a contractional step or bend in the fault plane associated with the lower dip segments. This geometry is investigated further with horizontal image logs and other borehole data to reveal a kinematic relationship between fault dip angle and mechanical stratigraphy. Field examples of normal faults that cut mechanically layered rock help better understand these complex fault geometries and provide reasonable inferences to their development and propagation history. In summary, it is argued that the mechanically layered nature of the Niobrara and Carlile formations is responsible for many of the fault characteristics described and provides valuable insight into understanding the fault system

A Late Pleistocene-Holocene natural seismograph along the Boconó Fault (Mérida Andes, Venezuela): the moraine-dammed Los Zerpa paleo-lake

2006 ◽  
Vol 177 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Eduardo Carrillo ◽  
Franck A. Audemard M. ◽  
Christian Beck ◽  
Michel Cousin ◽  
François Jouanne ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Younger Dryas ◽  
Late Glacial ◽  
Fault System ◽  
Tectonic Feature ◽  
Fine Grained ◽  
Temporal Correlations ◽  
Active Tectonic ◽  
The Caribbean ◽  
Sedimentary Fill

Abstract The Boconó Fault system is a major active tectonic feature accommodating an important part of the dextral relative motion between the Caribbean Plate and northern South-America. The main trace follows an axial valley running SW-NE within the Mérida Andes (northwestern Venezuela), and crosscuts a series of moraines related to late Pleistocene glaciers developments and retreats, at an altitude between 2600 and 5000 m. Several lakes were generated after the last retreat (between the Late Glacial Maximum –LGM– and the Younger Dryas re-advance), dammed by lateral and frontal moraines. Among them, the Los Zerpa moraine system yielded rich outcrops ranging from an upstream very coarse torrential to deltaic fill, to a downstream clayey-silty horizontal laminated lacustrine accumulation; a fore-set-type heterogeneous “prograding” body links the two sets. The whole system, as well as the surrounding moraines, underwent successive major earthquakes during the Late Glacial/lower Holocene period as evidenced by co-seismic scarps in the moraines, migrations of the outlet, and associated sagponds. Besides active faulting affecting both the moraines and the sedimentary fill, the latter –main purpose of our detail study– exhibits various evidence of strong disturbances which we relate to seismic shaking, such as: i) successive unconformities with co-seismic slips along fractures in the coarse proximal sediments; ii) successive dip changes, discontinuities, and slumps in the foreset-like set; iii) slumps with basal liquefaction, syn-sedimentary fractures, and instantaneous re-sedimentation in the fine-grained laminated accumulation. Lateral (temporal) correlations are established between the successive disturbances detected in the three situations; in turn, these sedimentary events are correlated with seismic activity of the Boconó Fault main trace. Thus, the whole paleo-lake may be considered as a natural seismograph which worked during several thousands years, after the end of the LGM and during early Holocene.

scholarly journals Diagenesis of Magnetic Minerals in Active/Relict Methane Seep: Constraints From Rock Magnetism and Mineralogical Records From Bay of Bengal

2021 ◽  
Vol 9 ◽  
Author(s):  
Virsen Gaikwad ◽  
Firoz Badesab ◽  
Pawan Dewangan ◽  
Mahender Kotha
Keyword(s):  
Magnetic Susceptibility ◽  
Bay Of Bengal ◽  
Rock Magnetism ◽  
Sediment Cores ◽  
Cold Seep ◽  
Fault System ◽  
Iron Sulfides ◽  
Magnetic Minerals ◽  
Fine Grained ◽  
Sediment Magnetism

In this study, we conducted a comprehensive investigation of rock magnetic, mineralogical, and sedimentological records of sediment cores supplemented by a high resolution seismic data to elucidate the controls of structural and diagenetic (early vs. late) processes on the sediment magnetism in active and relict cold seep sites in the Bay of Bengal. Two distinct sediment magnetic zones (Z-I and Z-II) are defined based on the down-core variations in rock magnetic properties. The sediment magnetism is carried by complex magnetic mineral assemblages of detrital (titanomagnetite, titanohematite) and authigenic (fine-grained greigite) minerals. Overall, the magnetic susceptibility varies over one order of magnitude with highest values found in relict core. Uppermost sediment magnetic zone (Z-I) is characterized by higher concentration of magnetite as seen through elevated values of magnetic susceptibility (χlf) and saturation isothermal remanent magnetization (SIRM). A systematic gradual decrease of χlf and IRM1T in Z-I is attributed to the progressive diagenetic dissolution of iron oxides and subsequent precipitation of iron sulfides. Magnetic grain size diagnostic (ARM/IRM1T) parameter decreases initially due to the preferential dissolution of fine-grained magnetite in the sulfidic zone (Z-I), and increases later in response to the authigenic formation of magnetite and greigite in methanic zone (Z-II). Distinct low S-ratio and χlf values in methanic zone of relict core is due to increased relative contribution from highly preserved coercive magnetic (titanohematite) grains of detrital origin which survived in the diagenetic processes. A strong linkage between occurrence of authigenic carbonates and greigite formation is observed. Two plausible mechanisms are proposed to explain the formation and preservation of greigite in Z-I and Z-II: 1) decline in methane flux due to massive hydrate accumulation within the active fault system and formation of authigenic carbonate crust in the sub-surface sediments hindered the supply of upward migrating fluid/gas; thereby limiting the sulfide production which preferentially enhanced greigite formation in Z-I and 2) restricted supply of downward diffusing sulfide by the carbonate layers in the uppermost sediments created a sulfide deficient zone which inhibited the pyritization and favoured the formation of greigite in the methanic zone (Z-II).

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