Comparative study of the transition between very low-grade and low-grade metamorphism in siliciclastic and carbonate sediments: Early Cretaceous, Cameros Basin (northern Spain)

Clay Minerals ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 407-419 ◽  
Author(s):  
J. Alonso-Azcarate ◽  
J. F. Barrenechea ◽  
M. Rodas ◽  
J. R. Mas
Keyword(s):  
Early Cretaceous ◽  
Burial Depth ◽  
Low Grade ◽  
Carbonate Sediments ◽  
Northern Spain ◽  
Grade Metamorphism ◽  
Mineral Assemblages ◽  
Great Heterogeneity ◽  
Cameros Basin ◽  
Facies Types

AbstractThe transition between very low-grade and low-grade metamorphism has been studied in the Urbión and Enciso Groups of the Late Jurassic-Early Cretaceous Cameros basin (NE Spain). The ‘illite crystallinity’ (IC) values do not appear to be controlled by burial depth but rather by: (1) XRD overlap with other phases (e.g. paragonite and mixed-layered muscovite-paragonite) in the siliciclastic samples; (2) the presence of carbonates, which delay illitization, resulting in an increase in the IC values, that becomes more pronounced as the P-T conditions decrease towards the diagenesis zone; and (3) the permeability of the sediments, which controls the circulation of metamorphic fluids and therefore the distribution of ‘crystallinities’ and mineral assemblages within the basin.The anchizone is represented by a narrow range of ‘chlorite crystallinity’ (ChC) values. Therefore, ChC is a less sensitive parameter than IC for estimating changes from diagenetic to low-grade metamorphic conditions. However, ChC can be a useful tool when there is a great heterogeneity of facies types, as it is not affected by the presence of carbonates.

Clay mineral variations associated with diagenesis and low-grade metamorphism of Early Cretaceous sediments in the Cameros Basin, Spain

Clay Minerals ◽  
1995 ◽  
Vol 30 (2) ◽  
pp. 119-133 ◽  
Author(s):  
J. F. Barrenechea ◽  
M. Rodas ◽  
J. R. Mas
Keyword(s):  
Clay Mineral ◽  
Early Cretaceous ◽  
Sudden Change ◽  
Burial Depth ◽  
Low Grade ◽  
Depositional Sequence ◽  
Depositional Sequences ◽  
Mineral Assemblages ◽  
Cameros Basin ◽  
Main Factor

AbstractThe clay mineral distribution in the Early Cretaceous depositional sequences along the Cameros Basin has been established on the basis of XRD traces and TEM/EDAX analyses. Samples from the Latest Berriasian-Barremian depositional sequences are characteristic of epimetamorphic conditions. Illite ‘crystallinities’ are broader than expected (0.35–0.490°Δ2θ), due to the consistent presence of K-mica-paragonite mixed-layer and discrete paragonite associated with the illite 10 Å peak. The Late Barremian-Early Aptian depositional sequence, around the depocentral sector of the basin, represents a sudden change to anchimetamorphic conditions, marked by the presence of pyrophyllite and rectorite and by a significant decrease in the A1IV content of the chlorites. Towards the northwestern border of the basin, this sequence was affected by deep diagenetic conditions, as deduced from the clay mineral association and the ‘crystallinity’ values (0.57°Δ2θ). The changes in the clay mineral assemblages and ‘crystallinity’ data can hardly be explained in terms of the varying burial depth and are related to changes in the circulation of fluids associated with varying facies (modal composition, grain size). Permeability is regarded as the main factor controlling the circulation of these migratory fluids.

scholarly journals Clay diagenesis and low-grade metamorphism of Tithonian and Berriasian sediments in the Cameros Basin (Spain)

Clay Minerals ◽  
2001 ◽  
Vol 36 (3) ◽  
pp. 325-333 ◽  
Author(s):  
J. F. Barrenechea ◽  
M. Rodas ◽  
M. Frey ◽  
J. Alonso-Azcárate ◽  
J. R. Mas
Keyword(s):  
Clay Mineral ◽  
Mixed Layer ◽  
Sedimentary Facies ◽  
Metamorphic Grade ◽  
Metamorphic Event ◽  
Low Grade ◽  
Grade Metamorphism ◽  
Mineral Assemblages ◽  
Cameros Basin ◽  
Southern Border

AbstractThe clay mineral assemblages of the Tithonian and Berriasian sediments (Tera and Oncala Groups) in the eastern part of the Cameros basin are investigated at seven localities. The lowest-grade assemblage, located on the southern border of the basin, contains calcite + quartz + hematite + kaolinite + mixed-layer illite-smectite (R = 1, 65 85% illite layers) + discrete illite (IC = 0.5 0.65Δ°2θ). Systematic increases in the illite and chlorite crystallinities suggest increasing metamorphic grade from the northwest part of the basin to the southeast. This trend does not follow the pattern previously described for the overlying late Berriasian–early Aptian sediments (Urbión and Enciso Groups), which exhibit a higher metamorphic grade. This may result from local variations in sedimentary facies, as well as the circulation of hot migratory fluids. Tertiary compression occurring long after the main metamorphic event is considered to be responsible for the enhanced illite and chlorite crystallinities measured in the SE extreme of the basin.

scholarly journals Clay minerals as provenance indicators in continental lacustrine sequences: the Leza Formation, early Cretaceous, Cameros Basin, northern Spain

Clay Minerals ◽  
2005 ◽  
Vol 40 (1) ◽  
pp. 79-92 ◽  
Author(s):  
J. Alonso-Azcárate ◽  
M. Rodas ◽  
J. F. Barrenechea ◽  
J. R. Mas
Keyword(s):  
Clay Mineral ◽  
Source Area ◽  
Local Source ◽  
Northern Spain ◽  
Source Areas ◽  
Kübler Index ◽  
Facies Associations ◽  
Mineral Assemblages ◽  
Cameros Basin

AbstractVariations in clay mineral assemblages, changes in Kübler index (KI), and the chemical composition of chlorites are used to identify source areas in the lacustrine materials in the Lower Cretaceous Leza Limestone Formation of the Cameros Basin, northern Spain. This formation has fairly homogeneous lithological characteristics and facies associations which do not allow for identification and characterization of local source areas. The Arnedillo lithosome of the Leza Limestone Formation contains a clay mineral association (Mg-chlorite, illite and smectite) indicative of its provenance. Chlorite composition and illite KI values indicate that these minerals were formed at temperatures higher than those reached by the Leza Formation which indicates its detrital origin. The similarity in the Mg-chlorite composition between the Arnedillo lithosome and the Keuper sediments of the area indicates that these materials acted as a local source area. This implies that Triassic sediments were exposed, at least locally, at the time of deposition of the Leza Formation. The presence of smectite in the Leza Formation is related to a retrograde diagenesis event that altered the Mg-chlorites in some samples.

Pathways and distances of fluid flow during low-grade metamorphism: evidence from pyrite deposits of the Cameros Basin, Spain

1999 ◽  
Vol 17 (4) ◽  
pp. 339-348 ◽  
Author(s):  
Alonso-Azcarate ◽  
Rodas ◽  
Bottrell ◽  
Raiswell ◽  
Velasco ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Low Grade ◽  
Grade Metamorphism ◽  
Cameros Basin

Evidence for low-grade metamorphism, hydrothermal alteration, and diagenesis on Mars from phyllosilicate mineral assemblages

2011 ◽  
Vol 59 (4) ◽  
pp. 359-377 ◽  
Author(s):  
Bethany L. Ehlmann ◽  
John F. Mustard ◽  
Roger N. Clark ◽  
Gregg A. Swayze ◽  
Scott L. Murchie
Keyword(s):  
Hydrothermal Alteration ◽  
Low Grade ◽  
Grade Metamorphism ◽  
Mineral Assemblages

Low-grade metamorphism and accretion tectonics: Southern Uplands terrain, Scotland

1985 ◽  
Vol 49 (352) ◽  
pp. 335-344 ◽  
Author(s):  
A. E. S. Kemp ◽  
G. H. J. Oliver ◽  
J. R. Baldwin
Keyword(s):  
Subduction Zones ◽  
Structural Data ◽  
Low Grade ◽  
Structural Level ◽  
Concomitant Increase ◽  
Illite Crystallinity ◽  
Grade Metamorphism ◽  
Trench Slope ◽  
Reflectance Data ◽  
Trajectory Characteristic

AbstractPrevious studies of low-grade metamorphism in the Southern Uplands accretionary terrain indicated prehnite-pumpellyite facies/anchizone conditions developed throughout the area, except for local preservation of trench-slope sediments and an accreted seamount at zeolite facies/advanced diagenetic grade. New graptolite reflectance data are presented that show a general northward increase in temperature in the Southern Uplands. The results from two cross-strike traverses in the southern and central belts in contemporaneous sequences, using illite crystallinity, illite lateral spacing (bo) , and graptolite reflectance, indicate the development of systematic accretion-related low-grade metamorphism. Well-developed and constant anchizone conditions occur throughout the NE (Langholm) traverse, associated with common, F1 accretion-related folding and a regionally penetrative S1 cleavage. In the SW (Kirkcudbright) traverse, however, the youngest, last accreted packets are preserved at a transitional diagenetic stage and lack a penetrative S1 cleavage. Illite crystallinity, graptolite reflectance, and bo increase systematically northward through earlier accreted packets, reaching values of the NE traverse only at the northern end. The concomitant increase of bo with illite crystallinity suggests the relatively high P-low T trajectory characteristic of subduction zones. Integration of metamorphic and structural data relates increasing intensity of aceretion-related F1 folding, developmertt of S1 fabric, and onset of later fold phases to grade of metamorphism and structural level within the accretionary pile.

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