Chlorite Clays Research Articles

Middle Miocene Stratigraphic Traps, Southeast Manila Village Field, Louisiana

ABSTRACT Southeast Manila Village Field, Louisiana, produces from two middle Fleming Group sandstones at depths ranging from 11,400 to 12,000 ft. Hydrocarbon production occurs mainly by a pressure deplion mechanism; a waterflood has been initiated to stabilize reservoir pressure. Fourteen wells have been drilled to date, and ultimate recovery from the field is estimated to be 4,609 MBO and 3,267 MMCFG. Thin sand bodies, designated as the 28 and 29 Sands, occur in a shale interval, which ranges in thickness from 500 to 600 ft. The reservoir rocks are thinly laminated, moderately to well-sorted, and very fine-grained sands. Thin sand laminations have sharp lower contacts with the interbedded shales, indicating episodic deposition. Foraminiferal assemblages indicate that the sands have been deposited in 100 to 400+ ft of water. The sands are probably the result of turbidity flow deposition in a distal-delta environment. Diagenetic reactions are, in part, responsible for the hydrocarbon accumulation in the sands. Dissolution of primary calcite cement and detrital K-feldspar grains has generated secondary porosity in the sands. Precipitation of authigenic minerals, such as chlorite, pyrite, siderite, kaolinite, illite, and mixed-layer clays has, however, influenced primary and secondary oil recovery. Migration and accumulation of hydrocarbons apparently halted secondary cementation by inhibiting the precipitation of authigenic clays.

Geologic Controls on the Production Characteristics of Cyclical, Mixed Carbonate-Clastic Gas Reservoirs, Lower Permian Chase Group. Guymon-Hugoton Field, Oklahoma: ABSTRACT

The Lower Permian Chase Group, Guymon-Hugoton field, Oklahoma, is composed of interlayered carbonates, siliciclastics, and evaporites deposited in cyclical, shallowing-upward sequences on a gently dipping, low-relief shelf. Each cycle forms a reservoir layer comprised of laterally continuous, successively shallower water marine carbonates and siliciclastics capped and separated by shaly red beds and paleosols. Reservoir studies indicate that individual reservoir layers have contrasting permeabilities and volumes, are not in pressure communication and exhibit different depletion characteristics. No virgin pressures have been revealed by recent drilling, indicating that no new gas has been discovered and that the current well-spacing pattern has been efficiently draining the field. Siltstones and sandstones consist of framework quartz, feldspar, mica, and rock fragments and interstitial clay, carbonate, and anhydrite; porosity is primarily intergranular. Within cycles, limy or dolomitic skeletal, pelletal, and oolitic subtidal grainstones to wackestones grade upward into intertidal to supratidal wackestones and mudstones. Intergranular and crystal- or grain-moldic pore types and a well-developed, laterally continuous, intercrystalline, pore system, produced by dolomitization and independent of depositional texture and other pore types, provide fair to excellent porosity and permeability within individual reservoir layers. Lateral continuity of the intercrystalline pore network and individual reservoir layers promotes good fieldmore » drainage. Shaly layers are composed of shaly mudstones and argillaceous carbonates that exhibit low permeabilities and high threshold entry pressures. Primary components include illitic, chloritic, and smectitic clays, authigenic carbonate and anhydrite, and detrital quartz, feldspar, and micaceous silt.« less

Use of Non-conventional Raw Materials for making Saggars

Applications of certain chloritic clays occurring in the state of Uttar Pradesh have been shown in the formation of cordierite—a low expansion ceramic material presently in great demand as kiln furniture in the pottery industry. The results indicate the importance of the nature of raw materials that take part in a specific ceramic formulation in the optimum firing temperature of industrial products obtained with them.

Sedimentology, Petrology, and Reservoir Characteristics of Lower Strawn Sandstone, Bent Tree Field, Hardeman County, Texas: ABSTRACT

Reservoir sandstones of the lower Strawn Formation (early Middle Pennsylvanian) in the Bent Tree field of Hardeman County, Texas, are coarse to fine-grained, texturally submature arkoses. Cores show the sandstones to have been deposited in 1.5-4.5 m thick fining-upward successions of aggraded or prograded bar units. Each bar unit has a sharp erosional base overlain by cross-bedded, coarse-grained, conglomeratic sandstone, which, in turn, is overlain by medium to fine-grained, horizontally bedded or ripple-bedded sandstone. The coarse conglomeratic sandstones are interpreted to represent deposition in main channels of a braided fluvial system that were progressively filled by aggrading and prograding bars. The interbedded, finer grained, more immature sandstones appear to have been deposited in auxiliary channels or swales, or in proximal overbank settings. The detrital framework grain suite of the reservoir sandstones averages 47% quartz, 30% feldspars, 19% igneous rock fragments, and 4% sedimentary rock fragments. The source of these sands was a plutonic/cratonic igneous massif with minor exposures of older sedimentary strata, and was probably the ancestral Wichita Mountains. Diagenesis has significantly affected the petrographic and reservoir properties of the lower Strawn sandstones, primarily through the in-situ alteration of detrital feldspathic grains and by the precipitation of authigenic quartz overgrowths,more » chlorite clay, and carbonate cements.« less

Petroleum Reservoirs in Silurian Dolomite of Western Illinois: ABSTRACT

The basal Silurian Alexandrian carbonates, sandwiched between the Ordovician-Silurian and Silurian-Devonian unconformities, have produced more than 3 million bbl of oil from the Buckhorn East and Brooklyn fields on the western margin of Illinois. These fields are shallow (450-670 ft), remote from the most-productive portion of the Illinois basin, and potential exists for additional production from this unconformity play. Three lithofacies were recognized in Alexandrian carbonates in detailed core and wireline studies that included thin-section, x-ray, and SEM analyses. These carbonates are regressive sequences composed of shallow-shelf, restricted-subtidal, and intertidal facies. The shallow-shelf facies is primarily biosparite composed of crinoid and brachiopod debris; t is facies is dolomitic in places. The restricted-subtidal facies consists of both bioturbated and undisturbed gray micrites containing stylolites, green chloritic clay, and glauconite; sparry clacite fills vertical cracks. The intertidal facies is tan, mottled, vuggy dolomite composed of algal mats, anhydrite-filled birdseye structures, burrows, and scattered marine fossils. Petroleum reservoirs apparently developed as a result of dolomitization in intertidal and shallow-shelf carbonates. Vuggy porosity, a possible result of karst leaching, is found in pay zones within the dolomitic intertidal facies. Evidence of emergence and subaerial weathering include the presence of vadose silt, anhydrite, and nontectonic breccia. End_of_Article - Last_Page 306------------

Rules of Sandstone Diagenesis Related to Reservoir Quality: ABSTRACT

The reservoir quality of sandstone is almost entirely controlled by diagenetic events. The chemical and physical processes responsible for diagenesis are complex and they influence sand during all stages of burial and, in some basins, during subsequent uplift. Petrographic studies by many workers in the past 10 years provide the basis for formulating rules of sandstone diagenesis that help in predicting reservoir quality in different End_Page 1215------------------------------ formations. Most of the rules listed below are empirical, and causative factors are still poorly understood. The list is also not complete. 1. The detrital mineral composition of a sand predetermines 50-80% of its diagenetic history. 2. Porosity lost by compaction cannot be regenerated during subsequent diagenetic events. Sands with abundant ductile grains (clay clasts, fecal pellets, shale clasts, micaceous rock fragments) can lose much primary porosity from the mashing of these grains during compaction. 3. The loss of primary porosity through compactional deformation of clays and ductile grains takes place during burial of 8,000-10,000 ft (2,450-3,050 m); loss of porosity by compaction at greater depths is by pressure solution of detrital grains. 4. Pressure solution of quartz grains is enhanced by the presence of grain coatings of illite and to a lesser degree by chlorite. 5. Quartz cement has an affinity for the coarser, more permeable sands in a formation. However, it rarely fills all pores in a sandstone except in some coarser grained laminae or in quartzarenites. 6. Carbonate cement may have a patchy distribution in a bed, but it fills all pores to produce a nonporous rock where it is present. 7. Carbonate cement is the dominant or only cement in sands with abundant carbonate fossil fragments or carbonate rock fragments; the carbonate cement is derived from the sand. 8. Poikilotopic calcite cement is the result of cementation that progressed from widely spaced nucleation sites. 9. Kaolinite forms by the replacement of feldspar and to a lesser degree of muscovite and also by free-standing growth in both primary and secondary pores. 10. Kaolinite should be expected as a diagenetic mineral in feldspar-rich sands (arkose and subarkose) that are poor in volcanic rock fragments. 11. Chlorite and/or mixed-layer clay should be expected as a diagenetic mineral in sandstone with more than 10% volcanic rock fragments. 12. Chlorite and mixed-layer clay, because of their tendency to bridge pores and produce baffles in pores, can seriously reduce permeability. 13. Early formed illite, typically present as grain coatings, does not seriously reduce permeability; late-formed illite tends to bridge pores and produce baffles and seriously reduce permeability. 14. Micrite cement is formed in continental sands above the water table. 15. Opal cement is formed in continental sands above the water table in stratigraphic sections where volcanic ash beds are intercalated with sands. 16. Some degree of secondary porosity is to be expected in a sandstone. However, there are few clues at present to predict the degree of secondary porosity or the cleanliness of secondary pores produced. Many secondary pores are micropores within incompletely dissolved feldspar or rock fragments. The best secondary pores are produced by dissolution of carbonate cement and evaporite cement. 17. Secondary porosity develops chiefly at depths greater than 6,000 ft (1,830 m) in the Gulf Coast, but can persist to depths of 20,000 ft (6,100 m). After their generation, secondary pores undergo some destruction during subsequent deeper burial by infilling with late-diagenetic ferroan carbonate and/or kaolinite. 18. Sands that had the greatest permeability at the time of deposition will develop the best secondary porosity. The best permeability will be in the coarsest, well-sorted sandstones (except in quartzarenites, where the coarsest beds selectively may undergo complete cementation by quartz). End_of_Article - Last_Page 1216------------

Compaction in Sandstones--Influence on Reservoir Quality: ABSTRACT

Primary porosity that is lost during burial through cementation by carbonate, evaporite, and some clay minerals can be regenerated during the stage of secondary porosity development that is typical of most basins. However, primary porosity that is lost through compaction is forever lost and cannot be regenerated. Thus, it is desirable to be able to predict the amount of porosity loss expected in sandstones buried to given depths. During progressive burial, terrigenous sandstones compact by (1) packing readjustments without changes in grain shape, (2) ductile deformation of clayey and micaceous grains, chiefly rip-up-clasts, fecal pellets, and fragments of shale, mudstone, slate, and schist, (3) bending of flexible micas, (4) pressure solution, and (5) fracturing of feldspar, quartz, and chert grains. Process 1 generally results in a 7-10% porosity loss and is independent of sandstone composition; processes 2, 3, and 4 are strongly dependent on framework composition and each by itself is responsible for producing tight sandstones; and process 5 is generally not important. Process 3 was modeled by Rittenhouse, who showed that sandstones with 35% ductile grains can compact to produce tight sandstones. Pressure solution becomes important at depths greater than 8,000 ft (2,400 m). Pressure solution at quartz grain contacts is enhanced where thick illite or chlorite clay coats develop and is most common in quartz-rich sandstones that lack much quartz cement. Quartz dissolved from grains generally exits the formation instead of being precipitated as cement. Stylolites develop at mica-rich and clay-rich laminae and develop conspicuous vertical permeability barriers. Wholesale dissolution of quartz grains leaves a residue of clay, micas, organic matter, and feldspar. End_of_Article - Last_Page 505------------

Bilelyeri Group, Antalya Complex: deposition on a Mesozoic passive continental margin, south‐west Turkey

ABSTRACTThe Bilelyeri Group comprises complexly deformed Mesozoic sedimentary rocks of continental‐margin affinities (Kumluca Zone). These are structurally intercalated between a coeval carbonate platform to the west (Bey Daǧlari Zone) and late Triassic ophiolitic rocks and sediments, interpreted as emplaced marginal oceanic crust, to the east (Gödene Zone). Four formations erected in the Bilelyeri Group record the later stages of continental rifting and the progressive development of part of a Mesozoic passive continental margin.The two late Triassic formations, the Telektaş Tepe and the Hatipalani Formations, are dominated by terrigenous clastic and calcareous clastic sediments, including large detached blocks of reef limestone. These rocks were laid down by mostly mass‐flow and turbidity‐flow into steep‐sided rift depressions. Organic reefs were constructed in bordering shallow seas while terrigenous clastic sediment was shed from exposed basement horsts. Thick sequences of mafic lavas were extruded (Norian) in axial parts of the rift zones, followed by a regional change to deposition of pelagic Halobia‐bearing limestone. This culminated in a major hiatus involving large‐scale sliding of shallow‐water limestones into deeper water.The Jurassic to early Cretaceous Dereköy Formation mostly consists of siltstones, radiolarian cherts and mudstones, intercalated with redeposited limestones and black shales. During this time parts of the margin were bordered by major offshore carbonate complexes constructed partly on basement fragments previously rifted off the parent continental areas. Black shales and reduced hemipelagic sediments were deposited in an elongate trough between the main platform and an offshore complex to the east. Some degree of margin reactivation in the early Cretaceous is indicated by renewed deposition of turbiditic sandstone and chloritic clays in some distal sequences. Strong relative enrichment of manganese in some horizons is attributed to offshore volcanic exhalations. Subsequent regional subsidence in the mid‐to late Cretaceous is suggested by a switch to predominantly calcareous, pelagic sedimentation on the adjacent platform and the offshore massifs as well as on the Bilelyeri margin.Tectonic disruption of the platform edge during the late Cretaceous is implied by major redeposition of shallow‐water shelf limestones in proximal Bilelyeri sequences. The Bilelyeri margin and the adjacent Gödene Zone were tectonically deformed in latest Cretaceous to early Tertiary time and were thrust over the adjacent Bey Daǧlari platform in the early Miocene.Viewed in an East Mediterranean perspective, the Bilelyeri sequences were part of a locally north‐south trending segment of a regionally east‐west margin to a substantial oceanic area further south. This segment apparently suffered significant strike‐slip deformation both during its construction and its later emplacement. Instructive comparisons can be made with other areas of the East Mediterranean, especially south‐west Cyprus.

Genesis of variegated redbeds in the fluvial Aztec Siltstone (late devonian), southern victoria land, Antarctica

The Aztec Siltstone (Late Devonian) formed in a meandering fluviatile environment and is a variegated redbed sequence consisting of red or drab overbank mudstones and drab channel sandstones, commonly arranged in fining-upwards cycles. The pigmentation in the red mudstones is caused by euhedral cryptocrystalline haematite which is dispersed throughout the matrix, masking the green colour of the underlying illitic and chloritic clays. Textural, mineralogical and chemical analyses suggest that the pigment formed in situ by dehydration and crystallization of a detrital, amorphous or poorly crystalline, yellow-brown ferric oxide precursor. The hydrated precursor apparently was derived from the weathering of iron silicates in a source area regolith, and transported in suspension with the Aztec alluvium, commonly by attachment onto surfaces of clay platelets. The association of the precursor with the clays is a contributing reason for the absence of red sandstones in the formation. Dehydration and crystallization of the yellow-brown ferric oxide to form the red haematite pigment occurred prior to deep burial of the host sediment. At least part of it occurred before burial, in an oxidising environment in well-drained and well-aerated overbank soils which were exposed for prolonged periods of time (4,000–10,000 years) under a hot and at least seasonally arid climate. Crystallization of the red pigment may have been completed during early diagenesis. Reducing conditions, induced by the presence of organic debris in the sediment and a relatively high water table, affected much of the deposit by removing the “free” hydrated ferric oxide, either partially or completely, from the in-channel sands, the low-lying and poorly drained overbank sediments, and the lacustrine sediments. This reduction was both a syndepositional and an early post-depositional process. Iron analyses indicate that, on average, the red mudstones are enriched in total iron (Fe) and Fe 3+ by 2%, all of which is attributable to the inherited “free” ferric oxide. There is no other significant difference in whole-rock mineralogy or major-element chemistry between the red and non-red mudstones.

Stimulation Techniques In the Milk River Formation, Medicine Hat

Abstract Recently, there has been a substantial level of activity in the shallow gas-bearing Milk River Formation of southeastern Alberta. Stimulation of the zone presents special problems, as the zone is soft, loosely consolidated, greatly affected by normal fracture fluids and low in permeability. Special materials and techniques have been developed to handle the particular problems presented by the Milk River Sand. This paper examines these techniques, including the use of carbon dioxide, large-mesh sand, clay-control agents and foaming agents, and estimates their effectiveness. The results of some treatments are discussed. Introduction THE MILK RIVER ZONE consists of two sections. The upper is a fine-grained, gray sandstone with interbedding of sandy clays and gray shales; the lower section is a light gray, medium-grained, cherty sandstone with streaks of sandy shale. The zone is found primarily in the southeastern portion of the province. Together with the overlying Pawkowki zone, the Milk River is equivalent to the Lea Park Formation. Zone thickness ranges up to 350 feet for the Pawkowki zone and 300 feet for the Milk River zone. Spectroscopic analysis indicates that the major component is quartzite, with small amounts of illite, kaolinite, chlorite and montmorillonite clays. This varies from well to well, and with depth, the deeper zone containing higher quantities of water-sensitive clays. Although there are very few cores cut on the Milk River zone, it appears that porosities range around 16 per cent, permeabilities are of the order of one milidarcy and water saturations are fairly high. Gas was first recovered from the Milk River zone in the year 1890. While exploring for coal in the Medicine Hat area, a well encountered considerable gas flows from a zone some 600 feet deep. Although little interest was shown in the Milk River section at that time, the gas discovery did spark gas well activity in the more prolific Medicine Hat Sand. However, activity was low because of the small size of local needs and because of the remoteness of any significant market. Of the few Milk River wells drilled in the early 1900's. one well, completed in 1911, continues to produce. Interest in the shallow gas, and particularly the Milk River zone, in southeastern Alberta remained dormant until 1941. At that time, the Department of National Defence drilled three wells to supply the Canadian Forces Base at Suffield with gas. By 1965 they had drilled some thirty wells, some of which are still on production for C.F.B. and Research Station use. Recent interest began late in 1968, with one well completed and put on production. The first frac treatment was also performed. Since that time, over two hundred fracture treatments have been conducted on the Milk River Sand with varying degrees of success. Various authors have described techniques of fracture geometry predictions, among them: Howard and Fast(2) Kiel(a), Geertsma and de Klerk'", As pointed out by Nierode et al(z), either of the most recent formulations give similar predictions of fracture geometry.

Activity of Co catalysts, deposited on Vietnam clays of kaolinite and chlorite type, in reaction for the hydropolymerization of ethylene initiated by carbon monoxide

The catalysts: Co-Vietnam white kaolinite clay (1∶2) and Co-Vietnam chlorite clay (1∶2), are active in the reaction for the hydropolymerization of ethylene, initiated by carbon monoxide.

Oxidation of Chlorites in Soil Clays and Effect on DTA Curves

IN general, the characteristic differential thermal analysis (DTA) curves of trioctahedral 14 A chlorites comprise three peaks: a single relatively large endothermic peak at about 450°–650° C produced by dehydroxylation of the hydroxide layer, a smaller endothermic peak, at about 700° C, due to dehydroxylation of the 2 :1 layer and an exothermic peak, between 750° and 900° C, due to decomposition of the mineral and recrystallization1,2. Mackenzie3 has shown that the DTA curves of chloritic clay fractions from soils seldom show these characteristic peaks and a recent investigation of some chlorite-rich soils in Scotland has confirmed this observation for clay fractions separated from freely drained soils (D. C. B., unpublished data). It was found that the DTA curves of chloritic clays from poorly drained gley soils, in which reducing conditions prevail for most of the time, did show these characteristic peaks. This difference in thermal behaviour is due to the fact that ferrous iron in the chlorite in freely drained soils has been oxidized.

Mineralogy of the Suspended Sediment in the Tigris, Euphrates, and Shatt-al-Arab Rivers of Iraq, and the Recent History of the Mesopotamian Plain

ABSTRACT Clay mineral fractions of the Euphrates and Tigris Rivers show marked differences related to the nature of the provenance area. The Euphrates is richer in both chlorite and expandable lattice clays. All the suspension load of the two rivers is deposited prior to entering the Persian Gulf. Minimum sediment accumulation in the lower Mesopotamian Plain is 0.1 cm/year, but if restricted to the marsh areas is 1.0 cm/year. Downwarp to form the present plain began in upper Miocene and is presently continuing. Marginal upwarping has occurred since human habitation of the region.

Clay Minerals in Hydrothermally Altered Rocks at Wairakei, New Zealand

AbstractGeothermal fluid discharged by steam wells, which have been core drilled to depths as much as 4500 ft at Wairakei, New Zealand, has altered Pliocene to Pleistocene, silicic, mainly glassy volcanics and related aqueous tuffs and breccias. Measured temperatures (max. 265°C) indicate epithermal to mesothermal conditions in buried fault fissures, the locus of both the hydrothermal fluid and most intense alteration.A supergene kaolinite alteration zone is distinguished from hypogene Ca-montmorillonite and combined micaceous and chloritic zones. The hypogene zones are usually wide and are temperature dependent and localized along fault fissures. Other common hypogene minerals are alkali feldspars, wairakite, epidote, quartz, calcite, laumontite, ptilolite, pyrite and pyrrhotite. Prehnite is rare.The micaceous clay minerals include illite (about 10 Å) and a series of random mixed-layer illite-montmorillonites with d(001) values ranging from 10·28 to 12·45 Å. The amount of interstratified montmorillonite is related to temperature and fault fissures. Apart from rare mixed-layer swelling chlorite, the Fe-rich chloritic clay shows little or no variation in its composition. Both the micaceous clays and the chloritic clay result from alteration of earlier formed Ca-montmorillonite.The stability of hydrothermal minerals is controlled by the temperature and chemical composition of the geothermal fluid ascending along the fault fissures. K-feldspar but not albite is deposited on fissure walls, but both alkali feldspars replace primary soda-lime plagioclase in the wall rock. The absence of albite on fissure walls is ascribed to low aqueous mNa+/mK+ ratio. Primary quartz is not affected by the altering solution but hydrothermal quartz is deposited on fissure walls and in the wall rock.

Tertiary Sedimentation in the Andaman-Nicobar Geosyncline

Abstract Andaman orthogeosyncline is continuous with Assam-Burma in the north and Indonesian geosyncline in the south. Andaman-Nicobar group of islands constituting the non-volcanic outer arc of the East Indian Orogen, has a more or less continuous history of Sedimentation throughout the Tertiary era commencing from sometime in the Upper Cretaceous right on to the Recent. The sedimentation gradually changed character with the tectonic development of the geosyncline through geologic time. Euxinic sediments consisting of black pyritous shales with minor amount or dark impure limestone and gritty sandstones represent the earliest episode of geosynclinal sedimentation in the restricted basins formed by submarine ridges and valleys due to emplacement of ophiolites. These ophiolites were subaerially denuded to some extent; and during Palaeocene-Lower Eocene, algal limestone and conglomerate and subsequently more finer fractions such as tuffaceous basic wacks and serpentinous and chloritic clay beds followed. Subsidence of the geosyncline which commenced with sedimentation of the Euxinic beds produced a uniform configuration of the geosyncline during Middle Eocene (Kirthar). Andaman flysch consisting of altetnatcly bedded graywackes, siltstone and grey illitic clay beds were deposited throughout the length and breadth in this regular geosynclinal basin till Upper Oligocene when a major orogenic movement overcame sedimentation. Shallower basins formed within and in the outer margins of the rising emhryonic island arc were filled up during Lower Miocene with foraminifcrallimcstone and shale, and radiolarian and foraminiferal chalk beds. Middle Miocene witnessed another major orogenic movement which brought out the present configuration of the island arc. Fossiliferous clays and limestones were deposited in peripheral basins during the Pliocene-Pleistocene which are partly raised during quite recent times.

Surface Sediments of Kara Sea, North of 76ø: ABSTRACT

End_Page 517------------------------------Two re-entrants or troughs extending from the Arctic basin into the northern Kara Sea, an epicontinental sea on the Eurasian continental shelf, were sampled during the summer of 1965. The program was limited to depths exceeding 100 fm. Distinct sedimentary zones exist in the westernmost trough which is open toward the southwest. These zones are expressed most strongly by the chlorite-kaolinite clay-group distribution which reflects a mixture from two distinct sources. The chlorite clays enter from the southwest and are dispersed northward along the eastern margin. The sedimentary zones depend more on the bottom relief, currents, and source than on the absolute water depth. The zones trend north-south, paralleling the dominant currents which consist of a north-flowing near-surface current on the east side and a south-flowing bottom current on the west. The zonation is shown on maps of clay-group facies, water content, insoluble residue, and organic carbon. Similar zonation is suggested by the distribution of the grain size, the composition of the sand-size clastic grains, and foraminiferal populations. In terms of relative amounts, the easternmost zone or slope is characterized by a low water content, and abundant chloritic clays, sand, and Foraminifera. The deposits at the foot of the slope have a high water and organic-carbon content, little chloritic material, and the greatest amounts of soluble material, though they contain few Foraminifera. The trough-floor sediments are characterized by an intermediate water content, low amounts of organic carbon, a very low chloritic content, and varying amounts of soluble material. The easternmost trough, which is open only to the Arctic, does not contain distinct sedimentary zones, nor does it have a recognizable current pattern. End_of_Article - Last_Page 518------------

Clay-Mineral Distribution in Permo-Pennsylvanian Shales of Val Verde Basin and Yates-Todd Arch, Texas

The purpose in studying the clay-mineral distribution in the Val Verde basin, Yates-Todd arch, and Midland basin of West Texas is to obtain information which will aid in working out the geologic history in this area. A knowledge of the geologic history will aid in locating oil or gas accumulations beneath the Permo-Pennsylvanian shale interval. A clay-mineral stratigraphic framework has been constructed from identifications of the clay minerals contained in these Permo-Pennsylvanian shales. Clay-mineral ratio profiles have been plotted from analyses of samples from 20 wells to make up this framework. Three clay-mineral zones can be traced consistently through the cross section represented by these wells. A lower zone (Zone I) contains illite, chlorite, kaolinite, mixed-layer clay, and small amounts of montmorillonite. A middle zone (Zone II) contains illite and minor amounts of chlorite, kaolinite and mixed-layer clay. Mixed-layer clay in this zone, however, is more abundant than in Zone I. An upper zone (Zone III) contains a richer assemblage of clays and is more variable than the two lower zones. The characteristic clays of Zone III are illite, chlorite, kaolinite, montmorillonite, vermiculite (?), and mixed-layer clay. Throughout most of the framework, the clay-mineral zone boundaries are favorably comparable with tentative electric log correlations. A major departure, however, occurs in the Magnolia's L. M. Morrison No. 1 of northwestern Val Verde County. This anomaly may reflect either large-scale thickening or the presence of additional section in this well. Zone I clay content is relatively homogeneous and correlatable variations are difficult to establish. Several wells in the Val Verde basin contain more than 5,000 feet of Zone I shale in which there is little variation in the clay content. A lower zone of relatively abundant chlorite, however, can be recognized in four wells. Chlorite is also more abundant in Zone I of the Val Verde basin than in Zone I of the Midland basin. Zone II is relatively uniform throughout the framework except in the Yates-Todd arch area. It is unidentifiable in two wells here. This absence reflects influence of the arch during Zone II deposition or is related to the geographic-oceanographic location of this area during Zone II time. Zone III is more variable both laterally and vertically. These variations could probably be correlated with more complete sampling. Abundant mixed-layer clay in this zone suggests slower deposition than that which occurred during Zone II time and (or) a different physical-chemical environment.

On the chlorite associated with gold ores

Chlorite associated with gold ore from the Oyama, Takahata, Osarizawa and Ani mines that are so-called epithermal ore deposits at Northern Japan, are studied mineralogically. In these ore deposits, 1) productive stage of gold ore is earlier than chloritic clay mineral stage, 2) chlorite associated with gold ore from the Oyama mine will agree repidolite, and chlorites from Takahata, Osarizawa, and Ani mine are ranged delessite-chloropite series chlorite.

Diagenetic Modification of Clay Mineral Types in Artificial sea Water

AbstractAnalyses of samples of kaolinitic, illitic, and montmorillonitic clay materials exposed to artificial sea water for periods of six months to five years have yielded some evidence to support the contention that chloritic and illitic clay types may ultimately develop from montmorillonitic material in the marine environment. However, no indications of the initiation or induction of any major lattice alteration of the original kaolinite and illitic type structures have been recognized on the basis of the data collected.The techniques of electron diffraction, electron microscopy, x-ray diffraction, and chemical analysis were employed to detect and measure the extent of modification of the clay materials at selected time intervals during the five year period.Actual separations of illitic-like and chloritic-like materials from treated montmorillonitic material were accomplished by gravitational settling methods. Relative weight percents of 18.2 for chloritic clay separates and 4.4 for illitic clay separates were obtained after more than four years of treatment. Chemical analysis and electron microscopy data suggest that lattice alteration preceded the development of forty to seventy percent of the chloritic and illitic material separated.The chloritic material apparently developed by initial formation of a magnesium-enriched montmorillonite having a hectoritic appearance. Subsequent development of threadlike extensions from the magnesium montmorillonite is shown by electron micrographs. These threads were observed to decrease or equilibrate in apparent amount within the chloritic separates as platelike forms began to appear after three years. The illitic separates were characterized by fine granulai material with increasing occurrence of larger platelike forms as exposure time increased.The modification of montmorillonitic clay was observed to be more dependent upon the magnesium-potassium ratio in the sea water than upon the total salt concentration levels. The limiting magnesium-potassium ratio was found to be approximately 9.4 with a limiting low potassium concentration of 0.005 moles per liter for montmorillonitic material of less than 0.5 micron settling diameter. The alteration of the montmorillonitic material was noted only for material that was initially settled through the artificial sea water media. As the potassium concentration level of these media dropped by extraction below 0.005 molar, a bulk effect of the settling material became operative and the relative percent of altered material decreased.Further, the relative amounts of modified material detected were decreased by the introduction of carbohydrate material into the sea water media. The amounts present after a definite time interval were also observed to be dependent upon the distributive tendencies of the source materials and the physical disturbance of the sea water media. Resuspension of the material by reagitation of the system decreased and significantly governed the rate of diagenetic modification.Special electron micrographs are presented to illustrate relative stages of flocculation of montmorillonitic material as the ionic concentration of sea water increases. It is suggested that these stages govern to an appreciable extent the extent and rate of initiation of any ionic exchange and lattice changes that occur.

CLAY MINERAL COMPOSITION OF SOME SEDIMENTS FROM THE PACIFIC OCEAN OFF THE CALIFORNIA COAST AND THE GULF OF CALIFORNIA

This report presents the results of a study of the clay mineral composition of a series of bottom core samples collected by the staff of the Scripps Institute of Oceanography of the University of California in Pacific Ocean off the California coast and in the Gulf of California. The clay minerals were studied by X-ray diffraction, differential thermal, optical, chemical, and electron microscopic methods following particle size fractionation by sedimentation and supercentrifuge procedures. All of the samples from the Pacific Ocean and from the Gulf of California contained illite, montmorillonite, and kaolinite; generally illite was most abundant and kaolinite least abundant. A chloritic clay mineral could be identified definitely in some samples. The clay minerals were in very complex mixtures, including mixed crystallizations as well as mechanical mixtures of discrete phases. In general the crystallinity was lower, the individual size smaller, and the intergrowth more intimate than in ancient sediments which have been studied by the authors. Small amounts of quartz were associated with the clay minerals in the 1 to 0.1 and minus 0.1 micron fractions. Small amounts of another nonclay mineral crystalline phase that is probably a feldspar were also found in the finest size fractions of many samples. The analytical data suggest that kaolinite is slowly lost during diagenesis under marine conditions, perhaps being changed to an illite or chloritic clay mineral. The data also afford evidence that potash is taken up by the clay and suggest that it is taken up largely by partially degraded illite which is carried into the sea. Magnesium also appears to be taken up by the clay, perhaps by the illite. The widespread occurrence of montmorillonite indicates that this clay mineral is not lost quickly if at all during diagenesis under marine conditions.