Canaveilles Group

The Canaveilles group is a metasedimentary rock sequence Neoproterozoic and Cambrian age, which occurs in the Pyrenees. It represents the oldest sequence purely sedimentary origin in this area dar.

Etymology

The Canaveilles group also Canaveilles series was named after its type locality Canaveilles in the department of Pyrénées -Orientales.

Distribution area

The distribution of Canaveilles group extends to the eastern Pyrenees region. In the more northern Montagne Noire, the southernmost foothills of the Massif Central, there is a similar sequence, the la Salvetat -Saint -Pons series. Also the upper Alcudium the Iberian Peninsula has similarities with the Canaveilles group. The emphasis in the spread of the group is in the vicinity of the type locality and framed the summit of the Canigou. However, it is also found on the Spanish side of the eastern Pyrenees in the Cadi - ceiling.

Stratigraphy

Near the type locality, the marine Canaveilles group reaches a thickness of up to 3000 meters, otherwise it varies between 2000 and 4000 meters. Your base superimposed on Canigou leptynitische transitional gneisses with underlying gneisses eyes. The group goes back to the Ediacaran back to around 580 million years. You essentially results in shales, and subordinate black shale and greywacke with carbonate intercalations and rhyodacite. In the area of ​​Cadi - ceiling Archaeocyatha Limestone also occur in the Lower Cambrian. The Canaveilles group is replaced on the border of the Middle Cambrian of the already somewhat weaker metamorphic ( greenschist facies, Chloritzone ) flyschoiden Jujols group, specifically from the basal, olistostromreichen Tregura formation of Jujols group.

Carbonate insertions

The Canaveilles group contains the type locality within its slate of four sequences of carbonate intercalations, which were metamorphosed to marbles and Kalksilikatgesteinen ( from hanging wall to footwall ):

• Sandy Kalksilikatgesteine
• Kalkmarmore
• Dolomite marbles
• Basal Kalkmarmore

Basal Kalkmarmore

The basal Kalkmarmore (French marbres de base ) up to 150 meters thick. They contain 5 layers Kalkmarmor, partly solid construction, and a layer of impure marbles, which have formed from Kalkareniten. The latter situation also leads gneisige liners decimeter, which consist of Kalksilikaten and are probably emerged from marls.

Dolomite marbles

The fine-grained, gray -beige colored dolomite marbles develop the mineral Chondrodite. In some locations also clinochlore and phlogopite may occur.

Between the dolomite marbles and the overlying Kalkmarmoren are several quartzite and greywacke levels.

Kalkmarmore

The white, sometimes gray banded Kalkmarmore are highly crystallized and are subject to considerable thickness changes. Your lying normally at around 20 meters thickness can locally increase up to 180 meters. These strong fluctuations suggest a rezifalen origins, probably is former bioherms.

Kalksilikatgesteine

The very fine-grained Kalksilikatgesteine ​​are formed gneiss -like. They have emerged from the former, very potassium-rich marls. You can have the character of multi-colored banded ( bright colors, greenish) hornfels accept and contain the minerals diopside, tremolite, clinozoisite, basic plagioclase, microcline and biotite microscopic.

Occur at the type locality on the Kalksilikatgesteine ​​in the form of sandy Kalkschiefern.

Rhyodazite

The former Rhyodazite, possibly rhyodacitic tuffs were metamorphosed to fine-grained Leptyniten. Stratigraphically they follow in the hanging wall of the basal Kalkmarmore, sometimes only above the Kalkmarmore. Radiometric age dating of the Rhyodaziten were 581 million years, confirming the age of the ediacarische Canaveilles group.

Formation

The Canaveilles group came during the Neoproterozoic and lower Cambrian in the former northern edge of Gondwana to the deposition. The sediments are of marine origin and were probably sold on the continental margin. Possible bioherms in the carbonate intercalations and Archaeocyathidenansammlungen in the Cadi - ceiling in the Cambrian suggest shelf or shelf margin deposits ( reefs ). The Rhyodazite may be the presence of an island arc suspect the Canaveilles group could thus well have been deposited in a backarc position. This is also their relationship to zentraliberischen Alcudium, a 15 kilometer (! ) Powerful, strong subsidenten, Neoproterozoic sedimentary series, which was probably along a transform fault, deposited on the active northern edge of Gondwana.

Metamorphosis

During the Variscan orogeny in the Pennsylvanian sediments of the Canaveilles group before 310 million years under mesozonalen conditions (lower amphibolite facies ) have been metamorphosed. The clayey portions of the sequence were in the lower portion of the group to mica schists of cordierite, andalusite and Sillimanitzone further up to greenschist facies phyllites of Biotitzone. The calcareous intercalations turned into marbles and Kalksilikatgesteine ​​. In Contact vicinity of the transition gneisses of andalusite Isograd and then the cordierite Isograd is crossed first. This indicates a intrusive origin of the gneisses as former granitoids.

Magmatism

The sedimentary sequence of the Canaveilles group is often crossed by two- mica granite corridors and associated pegmatites, which belong to the deep-seated granite of the Canigou. The igneous rocks intrude mainly the basal Kalkmarmore and dolomite marbles, but can also be found at higher elevations. In lower layers also diorites and tonalites can penetrate. The granitization took place after installation of ceiling structures towards the end of the Variscan orogeny.

Tectonics

The Canaveilles group was not only metamorphic overprinted during the Variscan orogeny but also strongly tectonically stressed. So it was, for example, the Canigou together with the gneisses and gneisses eyes ( former Ortho rocks ) is deformed into a giant lying Isoklinalfalte. Due to shearing in the legs formed two ceiling units, which were later further deformed plastically (internal folding) and also aufwölbten antiklinorisch. Upon reaching the brittle state it came under progressive narrowing then ( on the southern flank of the Canigou ) to On and back thrusts.

Since then, several revisions of the intrusion age of the orthogneiss find a unterordovizisches age of about 474 million years for the last crystallization was carried out on zircons, the conception of a Cadomian basement is no longer sustainable and the Isoklinalfaltenstruktur has thus become questionable. The nappe and subsequent deformations are not to doubt.

A further consequence of the intrusive nature of the orthogneiss is that which also held for the basement rocks, resulting from greywacke paragneiss series now also need to be counted for Canaveilles group, because they were only stronger metamorphic overprint during the Variscan orogeny.