Polyphase metamorphism in the eastern Carnic Alps (N Italy–S Austria): clay minerals and conodont Colour Alteration Index evidence

2007 ◽  
Vol 97 (6) ◽  
pp. 1213-1229 ◽  
Author(s):  
Covadonga Brime ◽  
Maria Cristina Perri ◽  
Monica Pondrelli ◽  
Claudia Spalletta ◽  
Corrado Venturini
Keyword(s):  
Clay Minerals ◽  
Carnic Alps ◽  
Conodont Colour Alteration Index ◽  
Polyphase Metamorphism ◽  
Colour Alteration

Metamorphic fluids and transtension in the Cantabrian Mountains of northern Spain: an application of the conodont colour alteration index

1986 ◽  
Vol 123 (6) ◽  
pp. 673-681 ◽  
Author(s):  
J. G. M. Raven ◽  
Ben A. Van Der Pluijm
Keyword(s):  
Large Scale ◽  
Fluid Transport ◽  
Spatial Relationship ◽  
Structural Features ◽  
Lower Permian ◽  
Low Grade ◽  
Northern Spain ◽  
Cantabrian Zone ◽  
Conodont Colour Alteration Index ◽  
Colour Alteration

AbstractConodont colour alteration index (CAI) values from Upper Paleozoic rocks in the Cantabrian zone of northern Spain show that temperatures during Hercynian metamorphism locally exceeded 300 °C. Various temperature domains have been defined, which are generally separated by fundamental structures. These domains do not correspond with the tripartite subdivision based on stratigraphic analysis.The observed CAI values of conodonts are in general agreement with the mineral paragenesis. Areas with high CAI values display extensive alteration and mineralization, and where CAI values exceed 4–4.5 (>200 °C) slaty cleavage has developed.The Cantabrian zone is an area of very low grade metamorphism, where peak conditions were reached in Upper Carboniferous to Lower Permian times. The characteristics of the metamorphism and its spatial relationship with major faults suggest that fluids were the main source for regional heating and that fluid transport was focussed along crustal-scale structural features.The overall deformation regime in this part of the Variscan orogen of western Europe is interpreted to be large-scale transtension. This is in agreement with earlier proposed models for the formation of Upper Palaeozoic basins in this area.

Thermal maturation of the Lower Palaeozoic strata of northern Greenland from conodont colour alteration index (CAI) data: implications for burial history and hydrocarbon exploration

1994 ◽  
Vol 131 (2) ◽  
pp. 219-230 ◽  
Author(s):  
H. A. Armstrong ◽  
M. P. Smith ◽  
R. J. Aldridge ◽  
S. J. Tull
Keyword(s):  
Carbonate Platform ◽  
Hydrocarbon Exploration ◽  
Thermal Maturity ◽  
Burial History ◽  
Thermal Maturation ◽  
The North ◽  
Conodont Colour Alteration Index ◽  
Lower Palaeozoic ◽  
Colour Alteration ◽  
North Greenland

AbstractConodont colour alteration data for the Lower Palaeozoic strata of the North Greenland carbonate platform indicate a pattern of increased thermal maturity northwards within the Franklinian Basin. There is little variation in values through the Canadian–Llandovery (Lower Ordovician–Lower Silurian) interval at any given locality. A simplified thermal model for the platform suggests that the predominant control of conodont colour alteration and thermal maturation was maximum depth of burial, which occurred during the mid- to late Silurian. A preliminary integrated scheme for conodont and organic thermal maturity indicators can be compiled from the data now available from North Greenland.

Tectonothermal evolution of a major thrust system: the Esla–Valsurbio unit (Cantabrian Zone, NW Spain)

2013 ◽  
Vol 150 (6) ◽  
pp. 1047-1061 ◽  
Author(s):  
SUSANA GARCÍA-LÓPEZ ◽  
FERNANDO BASTIDA ◽  
JESÚS ALLER ◽  
JAVIER SANZ-LÓPEZ ◽  
JOSÉ A. MARÍN ◽  
...  
Keyword(s):  
Geothermal Gradient ◽  
Contact Metamorphism ◽  
Coal Rank ◽  
Iberian Massif ◽  
Nw Spain ◽  
Cantabrian Zone ◽  
Fold And Thrust Belt ◽  
Conodont Colour Alteration Index ◽  
Thrust System ◽  
Colour Alteration

AbstractThe tectonothermal evolution of a unit in the foreland fold-and-thrust belt of the Iberian massif is established using the conodont colour alteration index (CAI). The unit consists of two parts with different tectonothermal histories – the Esla nappe region and the Valsurbio region – separated by a synorogenic Carboniferous basin (Guardo–Valderrueda basin). The Esla nappe region evolved in diacaizonal conditions (corresponding to the diagenetic conditions of the pelites) whose palaeotemperatures were controlled by rock burial. Maximum values were reached before the emplacement of the thrust nappes, so tectonic superimposition is not registered by the CAI. Overburial due to the emplacement of the thrust units was prevented by simultaneous intense erosion. The geothermal gradient obtained for burial wasc. 35 °C km−1and the temperature reached by the older Cambrian rocks wasc. 210–230 °C. The Valsurbio region was affected by an extensional tectonothermal post-orogenic event that gave rise to metamorphism with ancaizonal or epicaizonal conditions (corresponding to anchizone or epizone of the pelites). The most common maximum palaeotemperatures reached in this event fall within the range 305–415 °C, although higher palaeotemperatures could be reached locally as a consequence of contact metamorphism. This event gave rise to subhorizontal cleavage that cuts the main Variscan folds. Coal rank data indicate an increase in maximum palaeotemperatures eastwards from the Esla nappe region to the Valsurbio region through the Guardo–Valderrueda basin.

Graptolites as indicators of regional maturity in lower Paleozoic sediments, Selwyn Basin, Yukon and Northwest Territories, Canada

1989 ◽  
Vol 26 (10) ◽  
pp. 2003-2015 ◽  
Author(s):  
C. Riediger ◽  
F. Goodarzi ◽  
R. W. Macqueen
Keyword(s):  
Elevated Temperatures ◽  
High Heat ◽  
Active Member ◽  
Lower Paleozoic ◽  
Thermal Anomalies ◽  
Wide Range ◽  
Conodont Colour Alteration Index ◽  
Paleozoic Rocks ◽  
Reflectance Measurements ◽  
Colour Alteration

Variations in reflectance and bireflectance of graptolites and bitumen are documented from lower Paleozoic rocks of Howard's Pass (XY) Zn–Pb deposit and adjacent portions of the Selwyn Basin. Two types of graptolite morphologies are recognized in these rocks: a nongranular type, comprising blocky and lath-shaped varieties, and a granular type. The nongranular graptolites generally display higher reflectance and bireflectance than granular graptolites. Bitumen (epi-impsonite to meso-impsonite) is common in these rocks and displays a wide range of reflectance and bireflectance values.At the Howard's Pass (XY) property, graptolite-reflectance values display a slight increase with depth, and anomalously high values (7.46–10.25% [Formula: see text]) are documented in the sulphide-rich, upper Active Member. In surrounding regions of the Selwyn Basin, remote from Howard's Pass, graptolite-reflectance values are lower (3.02–6.26% [Formula: see text]). Conodont colour-alteration-index values reported by others show no detectable variation in the same rocks, which indicates that graptolite-reflectance measurements are more sensitive to variations in thermal maturity, at least for overmature sediments, than conodont colour-alteration index.The anomalously high reflectance values of both the graptolites and the bitumen from the Howard's Pass (XY) property, particularly in samples from the upper Active Member, indicate that these rocks have experienced elevated temperatures compared with regional values. This study demonstrates that graptolite-reflectance measurements may be used to delineate thermal anomalies. The integration of graptolite-reflectance and biostratigraphic studies in lower Paleozoic sequences is potentially useful for determining episodes of high heat flow.

Conodonts and corals in kimberlite xenoliths confirm a Devonian seaway in central Ontario and Quebec

2000 ◽  
Vol 37 (12) ◽  
pp. 1651-1663 ◽  
Author(s):  
Alexander D McCracken ◽  
Derek K Armstrong ◽  
Thomas E Bolton
Keyword(s):  
Sedimentary Rock ◽  
Late Ordovician ◽  
Stratigraphic Correlation ◽  
Lake Area ◽  
Early Devonian ◽  
Physical Evidence ◽  
Colour Changes ◽  
Conodont Colour Alteration Index ◽  
Colour Alteration ◽  
Age Determinations

Eighteen samples containing sedimentary rock xenoliths were obtained from cores drilled into eight Mesozoic kimberlite pipes in the Kirkland Lake area, Ontario, and in Ontario and Quebec near Lake Timiskaming. Nine samples from five pipes contained fossils that were used for age determinations. These fossils are Middle or Late Ordovician graptolites, inarticulate brachiopods, and conodonts; Silurian and (or) Devonian conodonts; Early Devonian colonial corals; a Devonian stromatoporoid; and Early to Middle Devonian conodonts. Regionally, conodonts are unaltered (conodont colour alteration index, CAI 1). Conodont CAI values from the xenoliths are elevated (CAI 2), and a few conodonts have surface colour changes, suggesting hydrothermal alteration. Age determinations allow stratigraphic correlation between xenoliths and Paleozoic outcrops. For the Ordovician and Silurian samples, correlations are made to exposures in the nearby Lake Timiskaming outlier. For the Devonian samples, the closest possible correlative outcrops are about 300 km away. These fossils provide the first physical evidence of a connection between a Lake Timiskaming "basin" and other Ontario basins during at least part of the Devonian. These strata persisted at least until the Mesozoic before they were removed by erosion.

Simultaneous use of thermal indicators to analyse the transition from diagenesis to metamorphism: an example from the Variscan Belt of northwest Spain

1997 ◽  
Vol 134 (3) ◽  
pp. 323-334 ◽  
Author(s):  
SUSANA GARCIA-LOPEZ ◽  
COVADONGA BRIME ◽  
FERNANDO BASTIDA ◽  
GRACIELA N. SARMIENTO
Keyword(s):  
Solution Temperature ◽  
Pressure Solution ◽  
Low Grade ◽  
Illite Crystallinity ◽  
Thermal Anomalies ◽  
Mineral Assemblages ◽  
Conodont Colour Alteration Index ◽  
Thermal Indicators ◽  
Inner Parts ◽  
Colour Alteration

The transition from diagenesis to very low-grade metamorphism has been characterized by conodont colour alteration index (CAI), illite crystallinity (IC), clay-mineral assemblages and rock fabric in a transect (Cape Peñas–Cape Torres) located in the Cantabrian Zone (northwest Spain). IC values show a northwest to southeast change from epizonal to diagenetic values. CAI values show a general congruence for low- and high-grade areas. This correlation indicates that CAI values for the epizone are >5.5, the anchizone 5.5≥CAI>4, and the diagenetic zone ≤4. Cleavage develops in incompetent rocks with CAI values greater than 3, mainly by pressure solution. Temperature increases towards the inner parts of the orogen (towards the northwest) and is considered to be related to the tectonic superposition caused by thrusting and folding. A gradient of 35°C/km is inferred for the transect. In the southeastern sector of the section there are several thermal anomalies that are attributed to the presence of epithermal fluids.

Conodont Colour Alteration Index (CAI) values for the Carboniferous of Scotland

1994 ◽  
Vol 85 (3) ◽  
pp. 211-220 ◽  
Author(s):  
Mark T. Dean ◽  
Nicholas Turner
Keyword(s):  
Qualitative Study ◽  
Low Temperatures ◽  
Thermal Effects ◽  
Geothermal Gradient ◽  
Petroleum Exploration ◽  
Hydrocarbon Generation ◽  
Igneous Intrusions ◽  
Conodont Colour Alteration Index ◽  
Local Average ◽  
Colour Alteration

AbstractConodont elements from Scottish Carboniferous rocks have been reviewed for Colour Alteration Index(CAI) data, and most values range between 1 and 1·5. Assuming a local average geothermal gradient similar to that of today, the observed and predicted CAI values generally fit well. Only a few of the samples analysed were influenced by local igneous intrusives. The CAI range shown lies within the immature (early dry gas) to mature (perhapsmid-oil window) stages of hydrocarbon generation, and this suggests that burial maturation (where CAI values are 1-5) could account for locally generated oil, where this occurred away from igneous intrusions. Alkali-dolerite and tholeiitic intrusives are, however, widespread in the Midland Valley of Scotland, and an understanding of their thermal effects has implications for both coal and petroleum exploration. The insensitivity of conodonts to low temperatures is noted, and the relevance, application and potential of various other palaeothermometers is discussed. Locally, the qualitative study of spore colour (SCI) appears useful.

Sign in / Sign up

Export Citation Format

Share Document