Cancarix volcano

Cancarix volcano
The Cancarix volcano from the south
height	707  msnm
location	Albacete Province , Spain
Mountains	Sierra de las Cabras
Notch height	250 m
Coordinates	38 ° 25 '2 "  N , 1 ° 35' 39"  W Coordinates: 38 ° 25 '2 "  N , 1 ° 35' 39"  W.
rock	Cancalit
Age of the rock	7.04 million years BP ( Messinian )

The Cancarix volcano is an extinct volcano near Cancarix south of Hellín in the southeastern Spanish province of Albacete . It is built from the very rare lamproite rock Cancalit . The volcano, active towards the end of the Miocene , belongs to the south-east Iberian volcanic province .

Occurrence

The volcano, 2 kilometers west of Cancarix and reaching 707 msnm , overlies the anticline structure of the Sierra de las Cabras , in whose Jurassic sediments the magma had penetrated. The volcanic building has been badly affected by the erosion. What has now been preserved is a thick-sheet structure made of solid, columnar cancalite and a phreatomagmatic breccia ring that girds it and underlies it .

geology

The Sierra de las Cabras underlying the Cancarix volcano is a broad, open, N 080-trending anticline, which is also locally formed as an anticlinorium. Tectonically, it belongs to the prebetic of the Betic Cordillera , the northernmost unit of the external zone. The sediments that make up it set in with 60 meters thick, massive limestone and dolomites of the Middle Jurassic, followed by 140 meters of marl-calcareous rhythms from the middle Oxfordian to the lower Kimmeridgian and 50 meters of oncolith limestone from the middle to upper Kimmeridgian. White limes and marls from the Cretaceous and calcarenites from the Upper Miocene are deposited above it . All of these sediments were affected by the folding . In the south and east of the volcanic building, the sediments of the anticline are traversed by steep, N 070 to N 090 traversing faults, which in some cases caused the anticline to be displaced up to a maximum of 200 meters to the south. This is followed by discordant conglomerates of the Pliocene and Pleistocene and the Quaternary debris . In the west of the volcano, two north-northeast trending side shifts (with an offset of 100 meters) cut the faults abruptly, so that the western part of the anticline is free of disturbances. The fault tectonics occurred roughly at the same time as the transtive, right- shifting Socovos Fault, which ran 30 kilometers further to the south-west and where numerous lamproites imposed. At the Cancarix volcano, one of the hidden faults in the north-western part of the volcano also served as the ascent path of the Cancalit magma.

description

The volcanic building is built on a cylindrical hilltop with a diameter of 900 meters, which protrudes 250 meters above the surrounding valley. It sits on the axial zone of the anticlinory and consists of 100 meters thick, massive Cancalitlava with columnar secretion. The vertical columns are continuous, but curve outwards at the base. Inside the lava dome, lamproit spheres with a diameter of 0.4 to 4 meters were created under the influence of weathering . The massive Cancalit dome is almost entirely girdled by a phreatomagmatic tuff ring of varying thickness, usually less than 22 meters. In the mechanically incompetent rhythm, however, the thickness increases to 24 meters, but decreases in the north and south-west to 8 meters, so that the lava body almost rests on the Jurassic carbonates. The tuff ring drops at 20 ° to 30 ° towards the center. The phreatomagmatic tuff ring can be divided into three facies (from hanging to lying ):

• Lava intermediate layers, generally less than 3 meters thick, can be further subdivided into
  • massive lavas
  • banded lavas rich in bubbles
• Layered phreatomagmatic breccia with layers in the meter range, further subdivided into
  • layers dominated by carbonates
  • layers dominated by pyroclasts
• Contact breccia of varying thickness (17 meters in the northwest, reduced to zero in the southeast)

The contact of the Cancalitlava with the underlying pyroclastics is normally flat, but can become very irregular if the lava is strongly self-brecciated.

A smaller, about 100 meters long, isolated volcanic deposit made of lava and ash sits in the eastern extension of the southern fault system. Reolid and colleagues (2013) interpret it as a lateral conveyor passage.

Volcanological development

The Cancarix volcano is a small volcanic complex with relatively low magma output. The magma rising to the surface was therefore dependent on a free ascent path, such as that represented by faults or fault zones. Since the extrusion itself is not affected by disturbances, it must have taken place after the fracture tectonics in the Upper Miocene. Two stages can be distinguished here:

• a highly explosive phase
• a quiet, emissive phase.

The explosive phase was dominated by phreatomagmatic eruptions, which were triggered by the contact of the magma with the groundwater of the karstified, fissured Jurassic sediments. The final emissive phase filled the explosion crater with massive Cancalitlava and lay over the tuff ring. The form of emission is still controversial here, a lava lake may have formed over the crater, but a viscous lava plug appears much more likely.

mineralogy

The Cancalit of the Cancarix volcano has phlogopite , sanidine and enstatite ( orthopyroxene ) as the predominant minerals . In addition to the titanium-rich phlogopite, the iron-rich sanidine and the enstatite, the minerals olivine (rich in the component forsterite ), Richterite ( amphibole with potassium and titanium), idiomorphic, prismatic diopside and leucite also appear . Furthermore, needle-shaped apatite , calcite , more rarely ilmenite , rutile and geikilite as well as accessory aegirin , akmit , dalyite and roedderite . Olivine and chromite can exist as xenocrystals .

Chemical composition

Main elements

Oxide wt.%	Cancarix	Cancarix 74A4	Standard mineral	CIPW standard 74A4
SiO 2	56.7	55.41	Q
TiO 2	1.54	1.41	Or	48.15
Al 2 O 3	9.23	8.83	Ac	3.57
Fe 2 O 3	4.80 (dead)	1.17	Ns	1.23
FeO		3.40	Ks	0.80
MnO	0.08	0.08	Tuesday	8.65
MgO	12.1	13.59	En	21.20
CaO	3.42	3.97	Fs	2.44
Na 2 O	0.78	1.13	Mt
K 2 O	9.11	8.63	Ilm	2.68
P 2 O 5	1.14	1.35	Ap	3.19
LOI	0.26	0.82
K / Na	7.67	5.03
K / Al	1.07	1.06
(Na + K) / Al	1.21	1.27

Sources: S. Duggen and colleagues (2005). For analysis 74A4: Wagner, C. and Velde, D. (1986)

The Cancalite of the Cancarix volcano is an ultrapotassic (K / Na> 3), intermediate alkali rock with a peralkaline character (da (Na + K) / Al> 1). It is characterized by very high contents of MgO and K ₂ O , whereas Na ₂ O is depleted. The occurrence of the standard minerals sodium metasilicate ( Ns ), potassium metasilicate ( Ks ) and Akmit ( Ac ) underlines the peralcalinity of the rock.

Trace elements

Trace elements ppm	Cancalit Cancarix volcano
Cr	1039
Ni	151
Zn	83.0
Rb	676
Sr	864
Zr	768
Ba	1694
Ce	293
Nd	186
Sm	34.5
Hf	23.8

As with all lamproites, the trace elements show an enrichment of the incompatible elements , especially the LILE rubidium and strontium , but also the HFSE thorium , cerium , zirconium , hafnium and the rare earths neodymium and samarium have increased values. The six-coordinate chromium also has very high concentrations.

Age

The Cancarix volcano from the southwest

The Cancarix volcano has been dated by Duggen and colleagues (2005) to 7.04 ± 0.01 million years BP and thus comes from the Messinian .

Individual evidence

1. ↑ Pérez-Voltera, LA et al .: Age distribution of lamproites along the Socovos fault (southern Spain) and lithospheric scale tearing . In: Lithos . tape 180-181 , 2013, pp. 252-263 .
2. ↑ Reolid, M. include: Natural Monument of the Volcano of Cancarix, Spain: a case of lamproite phreatomagmatic volcanism . In: Geoheritage . tape 5 , 2013, p. 35-45 , doi : 10.1007 / s12371-012-0072-2 .
3. ↑ Reolid, M. et al .: Phreatomagmatic activity and associated hydrothermal processes in the lamproitic volcano of Cancarix (Southeastern Spain) . In: Journal of Iberian Geology . tape 41 (2) , 2015, p. 183–204 , doi : 10.5209 / rev_JIGE.2015.V41.n2.46696 .
4. ↑ Duggen, S. et al .: Post-collisional transition from subduction to intraplate type magmatism in the westernmost Mediterranean: Evidence for continent-edge delamination of subcontinental lithosphere . In: Journal of Petrology . tape 46 , 2005, pp. 1155-1201 , doi : 10.1093 / petrology / egi013 .
5. ^ Wagner, C. and Velde, D .: The mineralogy of K-richterite-bearing lamproites . In: American Mineralogist . Volume 71, 1986, pp. 17-37 .
6. ↑ Duggen, S. et al .: Post-collisional transition from subduction to intraplate type magmatism in the westernmost Mediterranean: Evidence for continent-edge delamination of subcontinental lithosphere . In: Journal of Petrology . tape 46 , 2005, pp. 1155-1201 , doi : 10.1093 / petrology / egi013 .