Ihsan Al-aasm - Profile on Academia.edu (original) (raw)

Papers by Ihsan Al-aasm

AGUFM, Dec 1, 2016

Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Do... more Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Domain of southern Ontario, Canada. Core samples were analyzed for petrographic, stable and Sr isotopic composition, and fluid inclusion microthermometry to characterize dolomitization and evaluate diagenetic fluid composition. The samples represented a range of host rocks from dolomitized limestones, dolostones, sandy dolostones and sandstones within Ordovician Black River Group and underlying Cambrian formation. The petrographic and geochemical attributes have provided a basis to gain insight on the source fluids that modified these rocks, as well as, the possible timing of formation. Evidence indicates that the formations were subjected to high temperatures (average 115°C) that cannot be explained by burial history alone. This suggests the occurrence and migration of hydrothermal fluids within the low permeability dolomite horizons, possibly during Paleozoic orogenesis. Dolomite and calcite fracture infill isotopic and fluid inclusion data point to two possibly individual diagenetic fluid systems; i) an earlier Cambrian system that is characterized by a pronounced negative shifts in oxygen and carbon isotopic composition (δ 18 O average −9.0‰ for dolomite and −13.9‰ for calcite, respectively; and δ 13 C −3.06‰ for dolomite and −4.82‰ for calcite, respectively), a more radiogenic (Sr 87 /Sr 86 ratios range from 0.70977 to 0.71100), warm (Th values range from 84 to 156°C for dolomite; average 113.6°C and 87-141°C for calcite; average 101.5°C) and saline signature (salinity range from 23.2 to 27.2 wt% NaCl eq for dolomite; average 24.3 for dolomite and 23.6 wt% NaCl eq for calcite); and ii) a later Ordovician system that is characterized by less negative shifts in both oxygen and carbon isotopes (δ 18 O average −8.7 ‰for dolomite and −7.5‰ for calcite; and δ 13 C average + 0.37‰ for dolomite and −0.36‰ for calcite, respectively), hypersaline (salinity range from 22.4 to 30.1 wt% NaCl eq.; average 27.0 for dolomite and 27.5 to 29.7 for calcite; average 29.2), comparable homogenization temperature (Th ranges from 85 to 132°C for dolomite; average 109.6°C and 66-153°C for calcite; average 107.2°C) and a less radiogenic (Sr 87 /Sr 86 ratios range from 0.70818 to 0.71 000) fluid system. The observation of highly discrete, strata-bound dolomites combined with only trace quantities of saddle dolomite and its associated geochemical signature suggest that diagenesis, as a result of hydrothermal fluids, was neither pervasive in volume or extent within the north western Huron Domain.

International Journal of Coal Geology, Nov 1, 2020

This study presents results of laser ablation inductively coupled plasma mass spectrometry (LA-IC... more This study presents results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental analysis of scattered dolomite crystals in the Upper Ordovician Utica Shale of southern Québec to investigate the geochemical cause(s) of color variation in dolomite fluorescence and its possible relationship to thermal maturity. Utica Shale dolomite crystals show fluorescence zonation under ultraviolet (UV) light, with a shift from higher red/green quotient (R/G) in the crystal core to lower R/G in the crystal rims within dolomite crystal, while the crystal cores and rims R/G consistently increase with increasing thermal maturity. The LA-ICP-MS results show a consistent increase of Fe, Mn, Sr, Pb, and rare earth elements (REE) from crystal cores to rims, while Mg content shows the opposite trend. The decline in Mg content from the core to rim suggests depletion of Mg in the dolomitizing fluids during dolomite growth. Iron and Fe/Mn ratio are the only parameters that varied systematically with Mg content. The negative correlation between the red/green (R/G) quotient and Fe/Mn ratio suggests that temperature likely had an overarching effect on the chemistry of dolomite that ultimately controls the crystal zonation and its optical properties. Our data suggest that dolomite fluorescence can potentially be used as an alternative thermal maturity indicator in mudrocks with low organic content. However, compilation of a larger dataset is required to completely understand the relationship between dolomite R/G quotient and other established thermal maturity indicators.

The Formation of Septarian Concretions in Queen Charlotte Islands, B.C.: Evidence for Microbially and Hydrothermally Mediated Reactions at Shallow Burial Depth

Journal of Sedimentary Research, 1993

... ANDRI~ DESROCHERS Ottawa-Carleton Geoscience Centre Department of Geology Universily of Ottaw... more ... ANDRI~ DESROCHERS Ottawa-Carleton Geoscience Centre Department of Geology Universily of Ottawa Ottawa, Ontario KIN 6N5, Canada AND IHSAN S. AL ... 4). Concretion bod-ies are mainly composed of non-ferroan, fine-grained calcite (4-25 #m in size) with a neomorphic ...

Dolomitization, Neomorphism and Porosity Evolution: An Example from the Mississippian Upper Debolt Formation in the Blueberry Field, Northeastern British Columbia

Journal of Geochemical Exploration, Apr 1, 2006

Several researchers have suggested that upward and lateral hydrothermal fluid flow was responsibl... more Several researchers have suggested that upward and lateral hydrothermal fluid flow was responsible for dolomitization of various Devonian and Mississippian reservoirs in the Western Canada Sedimentary Basin (WCSB) based on sedimentological, geochemical and diagenetic evidence. In this study, a numerical model was applied to investigate hydrothermal fluid flow in the Wabamun Group, Parkland field, northeastern British Columbia, Canada. Our numerical results indicate that faults play the most critical role in controlling hydrothermal fluid flow. They provide a pathway connecting the basement of the basin and overlying sedimentary layers. Upwelling fluid flow via faults may bring reactants and heat from underlying strata to shallow formations for diagenetic reactions (e.g. dolomitization and/or chertification) or forming ore deposits. Salinity distribution of formation water, permeability configuration of host rock and regional fluid flow are also important factors affecting hot and brine fluid flow and accompanying heat and mass distribution.

Proceedings of the Ocean Drilling Program, Dec 1, 1996

Authigenic carbonates occur in thin layers, nodules, and burrows in fine-grained siliciclastic se... more Authigenic carbonates occur in thin layers, nodules, and burrows in fine-grained siliciclastic sediments of middle Eocene to Quaternary age that were recovered from the Arctic Ocean and Norwegian-Greenland Sea during Leg 151. At Site 913 (East Greenland Margin), concentrically zoned microspherules and rhombohedrons of ferroan rhodochrosite and manganoan siderite, 20-600 µm in diameter, are the main authigenic carbonates in the sedimentary succession. They grew displacively within the host clays and silts, and have locally coalesced to form aggregates. At Sites 909 (Fram Strait) and 911 (Yermak Plateau), very fine to fine-crystalline siderite, enriched in Ca and/or Mg, is the predominant carbonate in the sedimentary succession. It occurs as interparticle cement, disseminated crystals, and rounded intraclasts in host clays, silts, and muds. Minor micritic or radialfibrous calcite and dolomite were also found at these three sites. Most of these carbonates are interpreted to have precipitated at shallow-burial depths during early diagenesis. All authigenic carbonates (rhodochrosite, siderite, and calcite) from Site 913 are strongly enriched in 12 C (δ 13 C = -22.9 to -13.8%c) and show decreasing δ 13 C values with depth below the seafloor. This evidence, along with authigenic pyrite found in microspherule cores, suggests that dissolved carbon was derived from the oxidation of marine organic matter in the bacterial sulfate-reduction zone and during the early stages of methanogenesis. However, low organic matter content and headspace methane concentrations suggest additional derivation of dissolved carbon from thermogenic methane. The very low δ 18 θ values (-11.8%c) for rhodochrosite and the close association with barite in voids and fractures suggest rhodochrosite precipitation from Mn-charged, hydrothermal fluids, possibly related to volcanic activity associated with seafloor spreading. The δ 13 C values of most siderites from Site 909 are close to -6%c, which suggests an origin in the Fe-reduction, suboxic zone, possibly only centimeters or decimeters below the seafloor. However, minor occurrences of siderite with very low δ 13 C values (-21.8%c), along with their close association with authigenic pyrite, indicate additional derivation of dissolved carbon from bacterial sulfate-reduction and the early stages of methanogenesis. The importance of anaerobic microbial processes is further corroborated by the moderate to high organic matter content and headspace methane concentration at Site 909. The range of δ 18 θ values for siderite from Sites 909 and 911 (-10.3 to +5.0%o) appears to be related to both increasing burial temperatures and interaction between labile volcaniclastic sediment and marine pore waters.

Hydrothermal Dolomitization of the Mississippian Upper Debolt Formation, Sikanni Gas Field, Northeastern British Columbia, Canada

Bulletin of Canadian Petroleum Geology, Sep 1, 1997

The Mississippian carbonates of the Upper Debolt Formation, Sikanni Field, British Columbia, are ... more The Mississippian carbonates of the Upper Debolt Formation, Sikanni Field, British Columbia, are gas-producing, fractured and brecciated, dolomitized rocks. These rocks have undergone complex diagenetic changes, represented mainly by various generations of ...

Marine and Petroleum Geology, Apr 1, 2018

Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Do... more Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Domain of southern Ontario, Canada. Core samples were analyzed for petrographic, stable and Sr isotopic composition, and fluid inclusion microthermometry to characterize dolomitization and evaluate diagenetic fluid composition. The samples represented a range of host rocks from dolomitized limestones, dolostones, sandy dolostones and sandstones within Ordovician Black River Group and underlying Cambrian formation. The petrographic and geochemical attributes have provided a basis to gain insight on the source fluids that modified these rocks, as well as, the possible timing of formation. Evidence indicates that the formations were subjected to high temperatures (average 115°C) that cannot be explained by burial history alone. This suggests the occurrence and migration of hydrothermal fluids within the low permeability dolomite horizons, possibly during Paleozoic orogenesis. Dolomite and calcite fracture infill isotopic and fluid inclusion data point to two possibly individual diagenetic fluid systems; i) an earlier Cambrian system that is characterized by a pronounced negative shifts in oxygen and carbon isotopic composition (δ 18 O average −9.0‰ for dolomite and −13.9‰ for calcite, respectively; and δ 13 C −3.06‰ for dolomite and −4.82‰ for calcite, respectively), a more radiogenic (Sr 87 /Sr 86 ratios range from 0.70977 to 0.71100), warm (Th values range from 84 to 156°C for dolomite; average 113.6°C and 87-141°C for calcite; average 101.5°C) and saline signature (salinity range from 23.2 to 27.2 wt% NaCl eq for dolomite; average 24.3 for dolomite and 23.6 wt% NaCl eq for calcite); and ii) a later Ordovician system that is characterized by less negative shifts in both oxygen and carbon isotopes (δ 18 O average −8.7 ‰for dolomite and −7.5‰ for calcite; and δ 13 C average + 0.37‰ for dolomite and −0.36‰ for calcite, respectively), hypersaline (salinity range from 22.4 to 30.1 wt% NaCl eq.; average 27.0 for dolomite and 27.5 to 29.7 for calcite; average 29.2), comparable homogenization temperature (Th ranges from 85 to 132°C for dolomite; average 109.6°C and 66-153°C for calcite; average 107.2°C) and a less radiogenic (Sr 87 /Sr 86 ratios range from 0.70818 to 0.71 000) fluid system. The observation of highly discrete, strata-bound dolomites combined with only trace quantities of saddle dolomite and its associated geochemical signature suggest that diagenesis, as a result of hydrothermal fluids, was neither pervasive in volume or extent within the north western Huron Domain.

Stratigraphy, Stable Isotopes, and Hydrocarbon Potential of the Aptian Shuaiba Formation, U.A.E

SEPM (Society for Sedimentary Geology) eBooks, 2000

... of the United Arab Emirates (UAE), forms one of t.he most important petroleum reservoirs in .... more ... of the United Arab Emirates (UAE), forms one of t.he most important petroleum reservoirs in ... 69, Copyright © 2000 SEPM (Society for Sedimentary Geology), ISBN 1-56576-O75-1, p. 299 ... These samples came from both onshore and offshore fields in the UAE, including producing ...

The Effect of Hydrothermal Fluid Flow on Early Diagenetic Dolomitization: An Example from the Devonian Slave Point Formation, Northwest Alberta, Canada

The Middle Devonian carbonates of the Slave Point Formation, Hamburg field, northwestern Alberta,... more The Middle Devonian carbonates of the Slave Point Formation, Hamburg field, northwestern Alberta, are composed mainly of stromatoporoid and Amphipora floatstones and rudstones, with interbedded mudstone and grainstone facies characteristic of deposition in open to slightly restricted marine platform environments. These carbonates have undergone a complex diagenetic history, from shallow to deep burial, as represented by fracturing, calcite cementation, silicification, and dolomitization. Petrographically, four different types of dolomite have been identified (from early to late): (1) fine-crystalline matrix dolomite; (2) pseudomorphic dolomite; (3) medium-crystalline pervasive dolomite; and (4) saddle dolomite. Fine-crystalline dolomite (5– 50 m) replaces the mud matrix and slightly penetrates the edges of allochems. It occurred in mud-supported facies and was precipitated by marine fluids. Oxygen isotope values range from 11.62 to 9.34 (Peedee belemnite), lower than postulated values for Devonian carbonates. The enriched 87Sr/86Sr isotope value from this phase (0.71002) suggests that later diagenetic fluids may have recrystallized this dolomite. Pseudomorphic dolomite (50–100 m) replaces crinoids and occurs as single, large dolomite crystals. Its oxygen and carbon isotopic values range from 10.58 to 9.65 and +4.24 to +4.49, respectively. Medium-crystalline pervasive dolomite (10–100 m) occurs along dissolution seams and obliterates all previous fabrics. It is proposed that this medium-crystalline dolomite formed during shallow to intermediate burial because of its association with dissolution seams and high iron content. The range of oxygen isotope values for this dolomite (11.74 to 9.5) suggests precipitation from a warm fluid, possibly in a burial environment, and/or later recrystallization by hydrothermal fluids. The relatively wide range of carbon isotope values (+1.19 to +4.49) and enriched strontium isotope ratio (0.710020) suggests recrystallization. Saddle dolomite (250–2000 m) partially to completely occludes void spaces (both fractures and vugs) and also occurs as a minor replacement mineral. The oxygen isotope values for saddle dolomite (13.95 to 11.97), as well as the nonradiogenic to enriched strontium isotope ratios for saddle dolomite (0.70494 to 0.710351), and the fluid-inclusion data (homogenization temperature, Th, range between 125 and 161C and estimated salinity, between 22.2 and 24.7 wt.% NaCl equivalent) indicate precipitation from hot, highly saline, hydrothermal fluids, which were probably expelled tectonically during the Late Devonian–Mississippian Antler thrust belt development.

Diagenetic Evolution of Upper Jurassic-Lower Cretaceous Berdiga Formation, NE Turkey: Petrographic and Geochemical Evidence

Paleobiodiversity and Tectono-Sedimentary Records in the Mediterranean Tethys and Related Eastern Areas, 2019

Upper Jurassic-lower Cretaceous Berdiga Formation crops out extensively in NE Turkey. The host ca... more Upper Jurassic-lower Cretaceous Berdiga Formation crops out extensively in NE Turkey. The host carbonates at Eski Gumushane section are pervasively dolomitized by fabric-destructive and fabric-preserving replacive dolomites (RD). These dolomites are Ca-rich and non-stoichiometric (Ca56-58Mg42-44). They have highly variable but low δ18O (−11.38 to −4.05‰ V-PDB) and δ13C (0.69 to 3.13‰V-PDB) values, radiogenic 87Sr/86Sr ratios (0.70753 to 0.70884), extremely high Fe (2727–21053 ppm) and Mn (1548–27726 ppm) contents. Microcrystalline quartz cement, dolomite cement and the scattered euhedral pyrite minerals (average 5 μm) are also observed in the dissolution porosity of replacive dolomites. This study demonstrates that these carbonates have undergone a complex diagenetic history from shallow to deep burial associated with syn-sedimentary extensional tectonic activity during the Albian–Aptian and later with the hydrothermal emplacement of the polymetallic mineralization during the Eocene.

Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservoir sandstones: evidence from the Early Cretaceous Serraria Sandstones in the Sergipe-Alagoas Basin, NE Brazil

Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservo... more Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservoir sandstones: evidence from the Early Cretaceous Serraria Sandstones in the Sergipe-Alagoas Basin, NE Brazil

Paleomagnetic dating of diagenetic events in Paleozoic carbonate reservoirs of the Western Canada Sedimentary Basin

Paragenetic sequences for sedimentary rocks provide information on their geologic histories by es... more Paragenetic sequences for sedimentary rocks provide information on their geologic histories by establishing the order of diagenetic events such as compaction, mineral replacement, mineralization, fracturing and porosity evolution. Thus, a paragenetic sequence can be used to determine the age of a specific diagenetic event relative to other events. It is much more difficult to get an absolute age for that event. Direct radiometric dating of a specific mineral in the sequence will provide an absolute age date for the mineral, and the minimum and maximum age for the diagenetic events preceding and following, respectively. However, only a few studies have used radiometric techniques, either due to limitations of the techniques themselves or to a scarcity of datable minerals. Most studies of this type have been carried out on illite, calcite, glauconite, potassium feldspar and sphalerite, using Rb-Sr, U-Pb, 40Ar/39Ar, or Th-U-Pb techniques (e.g. Hearn et al. 1987; Smith et al. 1991; Dani...

Dolomitization of Mississippian Carbonates in the Shell Waterton Gas Field, Southwestern Alberta: Insights from Paleomagnetism, Petrology and Geochemistry

Bulletin of Canadian Petroleum Geology, 1998

Petrology, geochemistry and paleomagnetism have been collectively used to examine the process and... more Petrology, geochemistry and paleomagnetism have been collectively used to examine the process and timing of both dolomitization and hydrocarbon migration in carbonates from the Mississippian Mount Head Formation of the Shell Waterton gas field in the foothills of the Rocky Mountains of southwestern Alberta. Plugs were sampled from three unoriented drill cores and their azimuths were measured with respect to a master orientation line (MOL) on fitted segments of each core to provide the relative orientation between specimens from different plugs. The MOL azimuth was obtained by: 1) comparison of features observed in the core with those observed in the oriented Formation Micro-Scanner (FMS) logs; and, 2) aligning the low temperature magnetization direction with the present Earth's magnetic field (PEMF). Both methods gave similar results, showing that paleomagnetism can be an effective and inexpensive alternative for orienting drill core for which FMS logs are not available. Thermal...

Paleomagnetism, Petrology and Geochemistry of Mississippian Dolomites from the Shell Waterton Gas Field, Southwestern Alberta

Dating penecontemporaneous dolomitization in carbonate reservoirs: Paleomagnetic, petrographic, and geochemical constraints

AAPG Bulletin, 2003

The predominant dolomitization in the Mississippian Debolt Formation, Western Canada sedimentary ... more The predominant dolomitization in the Mississippian Debolt Formation, Western Canada sedimentary basin was hypothesized to be early in three gas fields, based on stable oxygen and carbon isotopic values and on strontium isotope ratios that are similar to postulated Mississippian dolomite values and seawater ratios, respectively. As the absolute age could not be determined by this method, paleomagnetism was used to place constraints on the age of the dolomitization. The magnetic analyses on Debolt specimens from the same wells revealed three magnetization components that could be tied to geologic/diagenetic events: (1) a low-temperature ( 350 degreesC) and coercivity (>80 mT) C component of primary or early diagenetic origin that is found mostly in the fine-grained limestone and dolomitic muds. The preservation of a primary or early diagenetic magnetization, combined with the preservation of primary isotopic values, indicates that little or no extrabasinal fluid flow is likely to ...

Diagenetic History and Isotope Geochemistry of Pabdeh Formation in Dezful Embayment (Zagros Basin) SW Iran

GEO 2010, 2010

Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale... more Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale -marl intervals. This Formation was studied the type section (Kuh-E-Gurpi) and four boreholes located in Dezful Embayment (Zagros Basin). The Pabdeh Formation comprises three depositional sequences bounded by Type I sequence boundary in lower part and both Type I and type II sequence boundaries in upper part. Uppermost sequence encompassed a subsea marine phreatic diagenetic environment, whereas sequence one and two evidently experienced burial diagenesis with moderately reducing conditions in a relatively enclosed system. Sr87/ Sr86 ratios represents a sharp separations between sequence two and three, whereas low Rb content of these samples suggesting these sediments are not affected by meteoric fluids in an open system. A double behaviour is expected from the Pabdeh Formation as the lithology are combination of carbonates and shale alternations, as shales could be considered as potential source rocks, whereas grainstones of tempestite facies have reservoir characteristics. Hence change of stratigraphic trap exploration is a scenario for these facies changes within the Pabdeh Formation. Furthermore, extensive fracturing in upper parts of second sequence implies reservoir porosity development in these parts. Evidences of meteoric water flushing implies in third (last) sequence, leads porosity development in this sequence.

Recognition of Palaeoexposure Surfaces within Cenomanian-Turonian Strata of Southwesterrn Iran: Implications for Reservoir Characteristics

GEO 2010, 2010

Recognition of Palaeoexposure Surfaces within Cenomanian-Turonian Strata of Southwesterrn Iran: I... more Recognition of Palaeoexposure Surfaces within Cenomanian-Turonian Strata of Southwesterrn Iran: Implications for Reservoir Characteristics. Elham Hajikazemi 1 ; Ihsan S. Al-Aasm 1 ; Mario Coniglio 2. ... Geological Magazine 143, 561-608. ...

Sequence Stratigraphy of Pabdeh Formation in Dezful Embayment (Zagros Basin) SW Iran

GEO 2010, 2010

Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale... more Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale -marl intervals. This Formation was studied the type section (Kuh-E-Gurpi) and four boreholes located in Dezful Embayment (Zagros Basin). The Pabdeh Formation comprises three depositional sequences bounded by Type I sequence boundary in lower part and both Type I and type II sequence boundaries in upper part. Uppermost sequence encompassed a subsea marine phreatic diagenetic environment, whereas sequence one and two evidently experienced burial diagenesis with moderately reducing conditions in a relatively enclosed system. Sr87/ Sr86 ratios represents a sharp separations between sequence two and three, whereas low Rb content of these samples suggesting these sediments are not affected by meteoric fluids in an open system. A double behaviour is expected from the Pabdeh Formation as the lithology are combination of carbonates and shale alternations, as shales could be considered as potential source rocks, whereas grainstones of tempestite facies of TST and HST in second sequence have reservoir characteristics. Hence change of stratigraphic trap exploration is a scenario for these facies changes within the Pabdeh Formation. Furthermore, extensive fracturing in upper parts of second sequence (late HST) implies reservoir porosity development in these parts. Evidences of meteoric water flushing implies in third (last) sequence, leads porosity development in this sequence.

AGUFM, Dec 1, 2016

Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Do... more Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Domain of southern Ontario, Canada. Core samples were analyzed for petrographic, stable and Sr isotopic composition, and fluid inclusion microthermometry to characterize dolomitization and evaluate diagenetic fluid composition. The samples represented a range of host rocks from dolomitized limestones, dolostones, sandy dolostones and sandstones within Ordovician Black River Group and underlying Cambrian formation. The petrographic and geochemical attributes have provided a basis to gain insight on the source fluids that modified these rocks, as well as, the possible timing of formation. Evidence indicates that the formations were subjected to high temperatures (average 115°C) that cannot be explained by burial history alone. This suggests the occurrence and migration of hydrothermal fluids within the low permeability dolomite horizons, possibly during Paleozoic orogenesis. Dolomite and calcite fracture infill isotopic and fluid inclusion data point to two possibly individual diagenetic fluid systems; i) an earlier Cambrian system that is characterized by a pronounced negative shifts in oxygen and carbon isotopic composition (δ 18 O average −9.0‰ for dolomite and −13.9‰ for calcite, respectively; and δ 13 C −3.06‰ for dolomite and −4.82‰ for calcite, respectively), a more radiogenic (Sr 87 /Sr 86 ratios range from 0.70977 to 0.71100), warm (Th values range from 84 to 156°C for dolomite; average 113.6°C and 87-141°C for calcite; average 101.5°C) and saline signature (salinity range from 23.2 to 27.2 wt% NaCl eq for dolomite; average 24.3 for dolomite and 23.6 wt% NaCl eq for calcite); and ii) a later Ordovician system that is characterized by less negative shifts in both oxygen and carbon isotopes (δ 18 O average −8.7 ‰for dolomite and −7.5‰ for calcite; and δ 13 C average + 0.37‰ for dolomite and −0.36‰ for calcite, respectively), hypersaline (salinity range from 22.4 to 30.1 wt% NaCl eq.; average 27.0 for dolomite and 27.5 to 29.7 for calcite; average 29.2), comparable homogenization temperature (Th ranges from 85 to 132°C for dolomite; average 109.6°C and 66-153°C for calcite; average 107.2°C) and a less radiogenic (Sr 87 /Sr 86 ratios range from 0.70818 to 0.71 000) fluid system. The observation of highly discrete, strata-bound dolomites combined with only trace quantities of saddle dolomite and its associated geochemical signature suggest that diagenesis, as a result of hydrothermal fluids, was neither pervasive in volume or extent within the north western Huron Domain.

International Journal of Coal Geology, Nov 1, 2020

This study presents results of laser ablation inductively coupled plasma mass spectrometry (LA-IC... more This study presents results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental analysis of scattered dolomite crystals in the Upper Ordovician Utica Shale of southern Québec to investigate the geochemical cause(s) of color variation in dolomite fluorescence and its possible relationship to thermal maturity. Utica Shale dolomite crystals show fluorescence zonation under ultraviolet (UV) light, with a shift from higher red/green quotient (R/G) in the crystal core to lower R/G in the crystal rims within dolomite crystal, while the crystal cores and rims R/G consistently increase with increasing thermal maturity. The LA-ICP-MS results show a consistent increase of Fe, Mn, Sr, Pb, and rare earth elements (REE) from crystal cores to rims, while Mg content shows the opposite trend. The decline in Mg content from the core to rim suggests depletion of Mg in the dolomitizing fluids during dolomite growth. Iron and Fe/Mn ratio are the only parameters that varied systematically with Mg content. The negative correlation between the red/green (R/G) quotient and Fe/Mn ratio suggests that temperature likely had an overarching effect on the chemistry of dolomite that ultimately controls the crystal zonation and its optical properties. Our data suggest that dolomite fluorescence can potentially be used as an alternative thermal maturity indicator in mudrocks with low organic content. However, compilation of a larger dataset is required to completely understand the relationship between dolomite R/G quotient and other established thermal maturity indicators.

The Formation of Septarian Concretions in Queen Charlotte Islands, B.C.: Evidence for Microbially and Hydrothermally Mediated Reactions at Shallow Burial Depth

Journal of Sedimentary Research, 1993

... ANDRI~ DESROCHERS Ottawa-Carleton Geoscience Centre Department of Geology Universily of Ottaw... more ... ANDRI~ DESROCHERS Ottawa-Carleton Geoscience Centre Department of Geology Universily of Ottawa Ottawa, Ontario KIN 6N5, Canada AND IHSAN S. AL ... 4). Concretion bod-ies are mainly composed of non-ferroan, fine-grained calcite (4-25 #m in size) with a neomorphic ...

Dolomitization, Neomorphism and Porosity Evolution: An Example from the Mississippian Upper Debolt Formation in the Blueberry Field, Northeastern British Columbia

Journal of Geochemical Exploration, Apr 1, 2006

Several researchers have suggested that upward and lateral hydrothermal fluid flow was responsibl... more Several researchers have suggested that upward and lateral hydrothermal fluid flow was responsible for dolomitization of various Devonian and Mississippian reservoirs in the Western Canada Sedimentary Basin (WCSB) based on sedimentological, geochemical and diagenetic evidence. In this study, a numerical model was applied to investigate hydrothermal fluid flow in the Wabamun Group, Parkland field, northeastern British Columbia, Canada. Our numerical results indicate that faults play the most critical role in controlling hydrothermal fluid flow. They provide a pathway connecting the basement of the basin and overlying sedimentary layers. Upwelling fluid flow via faults may bring reactants and heat from underlying strata to shallow formations for diagenetic reactions (e.g. dolomitization and/or chertification) or forming ore deposits. Salinity distribution of formation water, permeability configuration of host rock and regional fluid flow are also important factors affecting hot and brine fluid flow and accompanying heat and mass distribution.

Proceedings of the Ocean Drilling Program, Dec 1, 1996

Authigenic carbonates occur in thin layers, nodules, and burrows in fine-grained siliciclastic se... more Authigenic carbonates occur in thin layers, nodules, and burrows in fine-grained siliciclastic sediments of middle Eocene to Quaternary age that were recovered from the Arctic Ocean and Norwegian-Greenland Sea during Leg 151. At Site 913 (East Greenland Margin), concentrically zoned microspherules and rhombohedrons of ferroan rhodochrosite and manganoan siderite, 20-600 µm in diameter, are the main authigenic carbonates in the sedimentary succession. They grew displacively within the host clays and silts, and have locally coalesced to form aggregates. At Sites 909 (Fram Strait) and 911 (Yermak Plateau), very fine to fine-crystalline siderite, enriched in Ca and/or Mg, is the predominant carbonate in the sedimentary succession. It occurs as interparticle cement, disseminated crystals, and rounded intraclasts in host clays, silts, and muds. Minor micritic or radialfibrous calcite and dolomite were also found at these three sites. Most of these carbonates are interpreted to have precipitated at shallow-burial depths during early diagenesis. All authigenic carbonates (rhodochrosite, siderite, and calcite) from Site 913 are strongly enriched in 12 C (δ 13 C = -22.9 to -13.8%c) and show decreasing δ 13 C values with depth below the seafloor. This evidence, along with authigenic pyrite found in microspherule cores, suggests that dissolved carbon was derived from the oxidation of marine organic matter in the bacterial sulfate-reduction zone and during the early stages of methanogenesis. However, low organic matter content and headspace methane concentrations suggest additional derivation of dissolved carbon from thermogenic methane. The very low δ 18 θ values (-11.8%c) for rhodochrosite and the close association with barite in voids and fractures suggest rhodochrosite precipitation from Mn-charged, hydrothermal fluids, possibly related to volcanic activity associated with seafloor spreading. The δ 13 C values of most siderites from Site 909 are close to -6%c, which suggests an origin in the Fe-reduction, suboxic zone, possibly only centimeters or decimeters below the seafloor. However, minor occurrences of siderite with very low δ 13 C values (-21.8%c), along with their close association with authigenic pyrite, indicate additional derivation of dissolved carbon from bacterial sulfate-reduction and the early stages of methanogenesis. The importance of anaerobic microbial processes is further corroborated by the moderate to high organic matter content and headspace methane concentration at Site 909. The range of δ 18 θ values for siderite from Sites 909 and 911 (-10.3 to +5.0%o) appears to be related to both increasing burial temperatures and interaction between labile volcaniclastic sediment and marine pore waters.

Hydrothermal Dolomitization of the Mississippian Upper Debolt Formation, Sikanni Gas Field, Northeastern British Columbia, Canada

Bulletin of Canadian Petroleum Geology, Sep 1, 1997

The Mississippian carbonates of the Upper Debolt Formation, Sikanni Field, British Columbia, are ... more The Mississippian carbonates of the Upper Debolt Formation, Sikanni Field, British Columbia, are gas-producing, fractured and brecciated, dolomitized rocks. These rocks have undergone complex diagenetic changes, represented mainly by various generations of ...

Marine and Petroleum Geology, Apr 1, 2018

Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Do... more Strata-bound dolomite occurs in deep-seated Ordovician and Cambrian sediments within the Huron Domain of southern Ontario, Canada. Core samples were analyzed for petrographic, stable and Sr isotopic composition, and fluid inclusion microthermometry to characterize dolomitization and evaluate diagenetic fluid composition. The samples represented a range of host rocks from dolomitized limestones, dolostones, sandy dolostones and sandstones within Ordovician Black River Group and underlying Cambrian formation. The petrographic and geochemical attributes have provided a basis to gain insight on the source fluids that modified these rocks, as well as, the possible timing of formation. Evidence indicates that the formations were subjected to high temperatures (average 115°C) that cannot be explained by burial history alone. This suggests the occurrence and migration of hydrothermal fluids within the low permeability dolomite horizons, possibly during Paleozoic orogenesis. Dolomite and calcite fracture infill isotopic and fluid inclusion data point to two possibly individual diagenetic fluid systems; i) an earlier Cambrian system that is characterized by a pronounced negative shifts in oxygen and carbon isotopic composition (δ 18 O average −9.0‰ for dolomite and −13.9‰ for calcite, respectively; and δ 13 C −3.06‰ for dolomite and −4.82‰ for calcite, respectively), a more radiogenic (Sr 87 /Sr 86 ratios range from 0.70977 to 0.71100), warm (Th values range from 84 to 156°C for dolomite; average 113.6°C and 87-141°C for calcite; average 101.5°C) and saline signature (salinity range from 23.2 to 27.2 wt% NaCl eq for dolomite; average 24.3 for dolomite and 23.6 wt% NaCl eq for calcite); and ii) a later Ordovician system that is characterized by less negative shifts in both oxygen and carbon isotopes (δ 18 O average −8.7 ‰for dolomite and −7.5‰ for calcite; and δ 13 C average + 0.37‰ for dolomite and −0.36‰ for calcite, respectively), hypersaline (salinity range from 22.4 to 30.1 wt% NaCl eq.; average 27.0 for dolomite and 27.5 to 29.7 for calcite; average 29.2), comparable homogenization temperature (Th ranges from 85 to 132°C for dolomite; average 109.6°C and 66-153°C for calcite; average 107.2°C) and a less radiogenic (Sr 87 /Sr 86 ratios range from 0.70818 to 0.71 000) fluid system. The observation of highly discrete, strata-bound dolomites combined with only trace quantities of saddle dolomite and its associated geochemical signature suggest that diagenesis, as a result of hydrothermal fluids, was neither pervasive in volume or extent within the north western Huron Domain.

Stratigraphy, Stable Isotopes, and Hydrocarbon Potential of the Aptian Shuaiba Formation, U.A.E

SEPM (Society for Sedimentary Geology) eBooks, 2000

... of the United Arab Emirates (UAE), forms one of t.he most important petroleum reservoirs in .... more ... of the United Arab Emirates (UAE), forms one of t.he most important petroleum reservoirs in ... 69, Copyright © 2000 SEPM (Society for Sedimentary Geology), ISBN 1-56576-O75-1, p. 299 ... These samples came from both onshore and offshore fields in the UAE, including producing ...

The Effect of Hydrothermal Fluid Flow on Early Diagenetic Dolomitization: An Example from the Devonian Slave Point Formation, Northwest Alberta, Canada

The Middle Devonian carbonates of the Slave Point Formation, Hamburg field, northwestern Alberta,... more The Middle Devonian carbonates of the Slave Point Formation, Hamburg field, northwestern Alberta, are composed mainly of stromatoporoid and Amphipora floatstones and rudstones, with interbedded mudstone and grainstone facies characteristic of deposition in open to slightly restricted marine platform environments. These carbonates have undergone a complex diagenetic history, from shallow to deep burial, as represented by fracturing, calcite cementation, silicification, and dolomitization. Petrographically, four different types of dolomite have been identified (from early to late): (1) fine-crystalline matrix dolomite; (2) pseudomorphic dolomite; (3) medium-crystalline pervasive dolomite; and (4) saddle dolomite. Fine-crystalline dolomite (5– 50 m) replaces the mud matrix and slightly penetrates the edges of allochems. It occurred in mud-supported facies and was precipitated by marine fluids. Oxygen isotope values range from 11.62 to 9.34 (Peedee belemnite), lower than postulated values for Devonian carbonates. The enriched 87Sr/86Sr isotope value from this phase (0.71002) suggests that later diagenetic fluids may have recrystallized this dolomite. Pseudomorphic dolomite (50–100 m) replaces crinoids and occurs as single, large dolomite crystals. Its oxygen and carbon isotopic values range from 10.58 to 9.65 and +4.24 to +4.49, respectively. Medium-crystalline pervasive dolomite (10–100 m) occurs along dissolution seams and obliterates all previous fabrics. It is proposed that this medium-crystalline dolomite formed during shallow to intermediate burial because of its association with dissolution seams and high iron content. The range of oxygen isotope values for this dolomite (11.74 to 9.5) suggests precipitation from a warm fluid, possibly in a burial environment, and/or later recrystallization by hydrothermal fluids. The relatively wide range of carbon isotope values (+1.19 to +4.49) and enriched strontium isotope ratio (0.710020) suggests recrystallization. Saddle dolomite (250–2000 m) partially to completely occludes void spaces (both fractures and vugs) and also occurs as a minor replacement mineral. The oxygen isotope values for saddle dolomite (13.95 to 11.97), as well as the nonradiogenic to enriched strontium isotope ratios for saddle dolomite (0.70494 to 0.710351), and the fluid-inclusion data (homogenization temperature, Th, range between 125 and 161C and estimated salinity, between 22.2 and 24.7 wt.% NaCl equivalent) indicate precipitation from hot, highly saline, hydrothermal fluids, which were probably expelled tectonically during the Late Devonian–Mississippian Antler thrust belt development.

Diagenetic Evolution of Upper Jurassic-Lower Cretaceous Berdiga Formation, NE Turkey: Petrographic and Geochemical Evidence

Paleobiodiversity and Tectono-Sedimentary Records in the Mediterranean Tethys and Related Eastern Areas, 2019

Upper Jurassic-lower Cretaceous Berdiga Formation crops out extensively in NE Turkey. The host ca... more Upper Jurassic-lower Cretaceous Berdiga Formation crops out extensively in NE Turkey. The host carbonates at Eski Gumushane section are pervasively dolomitized by fabric-destructive and fabric-preserving replacive dolomites (RD). These dolomites are Ca-rich and non-stoichiometric (Ca56-58Mg42-44). They have highly variable but low δ18O (−11.38 to −4.05‰ V-PDB) and δ13C (0.69 to 3.13‰V-PDB) values, radiogenic 87Sr/86Sr ratios (0.70753 to 0.70884), extremely high Fe (2727–21053 ppm) and Mn (1548–27726 ppm) contents. Microcrystalline quartz cement, dolomite cement and the scattered euhedral pyrite minerals (average 5 μm) are also observed in the dissolution porosity of replacive dolomites. This study demonstrates that these carbonates have undergone a complex diagenetic history from shallow to deep burial associated with syn-sedimentary extensional tectonic activity during the Albian–Aptian and later with the hydrothermal emplacement of the polymetallic mineralization during the Eocene.

Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservoir sandstones: evidence from the Early Cretaceous Serraria Sandstones in the Sergipe-Alagoas Basin, NE Brazil

Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservo... more Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservoir sandstones: evidence from the Early Cretaceous Serraria Sandstones in the Sergipe-Alagoas Basin, NE Brazil

Paleomagnetic dating of diagenetic events in Paleozoic carbonate reservoirs of the Western Canada Sedimentary Basin

Paragenetic sequences for sedimentary rocks provide information on their geologic histories by es... more Paragenetic sequences for sedimentary rocks provide information on their geologic histories by establishing the order of diagenetic events such as compaction, mineral replacement, mineralization, fracturing and porosity evolution. Thus, a paragenetic sequence can be used to determine the age of a specific diagenetic event relative to other events. It is much more difficult to get an absolute age for that event. Direct radiometric dating of a specific mineral in the sequence will provide an absolute age date for the mineral, and the minimum and maximum age for the diagenetic events preceding and following, respectively. However, only a few studies have used radiometric techniques, either due to limitations of the techniques themselves or to a scarcity of datable minerals. Most studies of this type have been carried out on illite, calcite, glauconite, potassium feldspar and sphalerite, using Rb-Sr, U-Pb, 40Ar/39Ar, or Th-U-Pb techniques (e.g. Hearn et al. 1987; Smith et al. 1991; Dani...

Dolomitization of Mississippian Carbonates in the Shell Waterton Gas Field, Southwestern Alberta: Insights from Paleomagnetism, Petrology and Geochemistry

Bulletin of Canadian Petroleum Geology, 1998

Petrology, geochemistry and paleomagnetism have been collectively used to examine the process and... more Petrology, geochemistry and paleomagnetism have been collectively used to examine the process and timing of both dolomitization and hydrocarbon migration in carbonates from the Mississippian Mount Head Formation of the Shell Waterton gas field in the foothills of the Rocky Mountains of southwestern Alberta. Plugs were sampled from three unoriented drill cores and their azimuths were measured with respect to a master orientation line (MOL) on fitted segments of each core to provide the relative orientation between specimens from different plugs. The MOL azimuth was obtained by: 1) comparison of features observed in the core with those observed in the oriented Formation Micro-Scanner (FMS) logs; and, 2) aligning the low temperature magnetization direction with the present Earth's magnetic field (PEMF). Both methods gave similar results, showing that paleomagnetism can be an effective and inexpensive alternative for orienting drill core for which FMS logs are not available. Thermal...

Paleomagnetism, Petrology and Geochemistry of Mississippian Dolomites from the Shell Waterton Gas Field, Southwestern Alberta

Dating penecontemporaneous dolomitization in carbonate reservoirs: Paleomagnetic, petrographic, and geochemical constraints

AAPG Bulletin, 2003

The predominant dolomitization in the Mississippian Debolt Formation, Western Canada sedimentary ... more The predominant dolomitization in the Mississippian Debolt Formation, Western Canada sedimentary basin was hypothesized to be early in three gas fields, based on stable oxygen and carbon isotopic values and on strontium isotope ratios that are similar to postulated Mississippian dolomite values and seawater ratios, respectively. As the absolute age could not be determined by this method, paleomagnetism was used to place constraints on the age of the dolomitization. The magnetic analyses on Debolt specimens from the same wells revealed three magnetization components that could be tied to geologic/diagenetic events: (1) a low-temperature ( 350 degreesC) and coercivity (>80 mT) C component of primary or early diagenetic origin that is found mostly in the fine-grained limestone and dolomitic muds. The preservation of a primary or early diagenetic magnetization, combined with the preservation of primary isotopic values, indicates that little or no extrabasinal fluid flow is likely to ...

Diagenetic History and Isotope Geochemistry of Pabdeh Formation in Dezful Embayment (Zagros Basin) SW Iran

GEO 2010, 2010

Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale... more Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale -marl intervals. This Formation was studied the type section (Kuh-E-Gurpi) and four boreholes located in Dezful Embayment (Zagros Basin). The Pabdeh Formation comprises three depositional sequences bounded by Type I sequence boundary in lower part and both Type I and type II sequence boundaries in upper part. Uppermost sequence encompassed a subsea marine phreatic diagenetic environment, whereas sequence one and two evidently experienced burial diagenesis with moderately reducing conditions in a relatively enclosed system. Sr87/ Sr86 ratios represents a sharp separations between sequence two and three, whereas low Rb content of these samples suggesting these sediments are not affected by meteoric fluids in an open system. A double behaviour is expected from the Pabdeh Formation as the lithology are combination of carbonates and shale alternations, as shales could be considered as potential source rocks, whereas grainstones of tempestite facies have reservoir characteristics. Hence change of stratigraphic trap exploration is a scenario for these facies changes within the Pabdeh Formation. Furthermore, extensive fracturing in upper parts of second sequence implies reservoir porosity development in these parts. Evidences of meteoric water flushing implies in third (last) sequence, leads porosity development in this sequence.

Recognition of Palaeoexposure Surfaces within Cenomanian-Turonian Strata of Southwesterrn Iran: Implications for Reservoir Characteristics

GEO 2010, 2010

Recognition of Palaeoexposure Surfaces within Cenomanian-Turonian Strata of Southwesterrn Iran: I... more Recognition of Palaeoexposure Surfaces within Cenomanian-Turonian Strata of Southwesterrn Iran: Implications for Reservoir Characteristics. Elham Hajikazemi 1 ; Ihsan S. Al-Aasm 1 ; Mario Coniglio 2. ... Geological Magazine 143, 561-608. ...

Sequence Stratigraphy of Pabdeh Formation in Dezful Embayment (Zagros Basin) SW Iran

GEO 2010, 2010

Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale... more Pabdeh Formation (upper Eocene-Oligocene) is a carbonate dominated sedimentary package with shale -marl intervals. This Formation was studied the type section (Kuh-E-Gurpi) and four boreholes located in Dezful Embayment (Zagros Basin). The Pabdeh Formation comprises three depositional sequences bounded by Type I sequence boundary in lower part and both Type I and type II sequence boundaries in upper part. Uppermost sequence encompassed a subsea marine phreatic diagenetic environment, whereas sequence one and two evidently experienced burial diagenesis with moderately reducing conditions in a relatively enclosed system. Sr87/ Sr86 ratios represents a sharp separations between sequence two and three, whereas low Rb content of these samples suggesting these sediments are not affected by meteoric fluids in an open system. A double behaviour is expected from the Pabdeh Formation as the lithology are combination of carbonates and shale alternations, as shales could be considered as potential source rocks, whereas grainstones of tempestite facies of TST and HST in second sequence have reservoir characteristics. Hence change of stratigraphic trap exploration is a scenario for these facies changes within the Pabdeh Formation. Furthermore, extensive fracturing in upper parts of second sequence (late HST) implies reservoir porosity development in these parts. Evidences of meteoric water flushing implies in third (last) sequence, leads porosity development in this sequence.