Verit

Verite is a very rare igneous rock that belongs to the lamproites , more precisely to the phlogopite lamproites. The Verit belongs to the southeast Iberian volcanic province .

First description and occurrence

The Cabezo María near Antas , a former volcano from Verit

The Verit was scientifically described for the first time in 1889 by Carl Alfred Osann . The rock was named after its type locality - Vera in the province of Almería in Andalusia . Five Verit occurrences are quite close to each other about 15 to 20 kilometers away south of Vera, furthermore the separate occurrence of a volcano can be found about 70 kilometers northeast near La Aljorra .

Petrology

The rock was originally described by Osann as black pitch stone , which was associated with extrusions from Fortunit . It consisted of phenocrystals of phlogopite and olivine that floated in a glassy matrix. The matrix itself contained microliths of diopside and phlogopite. In the new Lamproit classification, the rock is now referred to as hyalo-olivine-diopside phlogopite - lamproit .

The Verit appears in the southern surroundings of Vera in various forms, for example as a laccolith , as a lopolite or as a composite form on the Cabezo María , where Peperite and Scoria are covered by a lava flow .

mineralogy

The phenocrystals in Verit are chromium- containing, forsterite- rich olivine of the composition Fo _90-95 and needle-shaped to tabular phlogopite. The glassy base mass, which takes up to over 70 percent by volume, contains microcrystals of phlogopite, diopside, sanidine , leucite and apatite . Secondary calcite has formed in bubble-shaped cavities . Occasional xenocrystals of olivine can be found in the rock , which contain inclusions of spinel and suggest a place of origin in the upper mantle .

In the quarry on Verit of La Aljarra, the following accessories can be found in addition to the minerals already mentioned: the oxides hematite , magnetite and ilmenite , the mixed series armalcolite - pseudobrookite , fluorophlogopite , enstatite , tridymite , opal and warwickite .

Chemical composition

Main elements

Oxide wt.%	Verit bandwidth	Verit SP 011	Verit VER-4	Verit ALJ-1	Verit Alm-01	Verit Alm-02
SiO ₂	55.33-66.50	66.50	55.33	54.05	58.1	54.7
TiO ₂	0.91-1.71	1.45	1.40	0.91	1.71	1.54
Al ₂ O ₃	9.82-13.35	9.82	10.70	13.35	10.90	10.80
Fe ₂ O ₃	0.99-5.33 (dead)	3.59 (dead)	0.99	5.31	1.11	0.50
FeO	1.09-3.96		3.96	1.09	3.59	4.10
MnO	0.03-0.11	0.03	0.08	0.11	0.07	0.07
MgO	2.53-11.91	2.68	11.91	8.37	3.52	7.58
CaO	2.25-7.28	2.25	2.92	7.28	6.70	4.99
Na ₂ O	1.11-2.94	1.11	2.93	1.39	1.89	2.84
K ₂ O	3.47-7.34	7.34	3.48	5.77	6.82	3, 74
P ₂ O ₅	0.54-0.81	0.54	0.63	0.65	0.76	0.60
LOI	1.74-8.81		5.18	1.74	5.54	8.81

Sources: Conticelli, S. and colleagues (2009) and Benito, R. and colleagues (1999)

Verite is an intermediate, mostly metaluminous (with (Na + K) / Al <1) rock with a high content of Na ₂ O , but only moderate K ₂ O (potassic).

Trace elements

! Trace elements ppm	Verit bandwidth	Verit SP 011	Verit VER-4	Verit ALJ-1	Verit Alm-01	Verit Alm-02
Cr	528-722	581	722	666	610	550
Ni	157-617	157	617	392	300	290
Zn	50.0-70.2	65.3		50	60
Rb	265-592	514	473	265	444	389
Sr	441-501	448	441	466	484	467
Zr	294-814	624	649	294	643	672
Ba	1384-1815	1384	1554	1596	1580	1550
Ce	173-267	236	253	173	267	252
Nd	104-170	128	159	104	155	149
Sm	18.0-28.1	23.7	25.6	18.0	28.1	26.8
Hf	9.9-18.9	16.6	17.80	9.90	18.9	18.4
Th	73.4-101.7	73.4	90.6	82.4	83.0	78.7

With the trace elements Verit shows an extreme accumulation of the incompatible elements . Negative spikes are found on the LILE barium and strontium as well as niobium and titanium . The HFSE are enriched in lead , neodymium , thorium , uranium and gadolinium .

Isotope ratios

Neodymium-strontium isotope diagram with the position of the verites (V) compared to other lamproites

Isotopes	Verit SP 011	Verit Alm 01	Verit Alm 02	Verit VER-4	Verit ALJ-1
⁸⁷ Sr / ⁸⁶ Sr	0.720729	0.722591	0.722510	0.720980	0.719740
¹⁴³ Nd / ¹⁴⁴ Nd	0.512013	0.512019	0.512009
²⁰⁶ Pb / ²⁰⁴ Pb	18.797	18,790	18.786
²⁰⁷ Pb / ²⁰⁴ Pb	15.693	15.696	15.690
²⁰⁸ Pb / ²⁰⁴ Pb	39.025	39.012	38.998
ô ¹⁸ O				11.1	10.2

The isotope ratios are constantly low, ¹⁴³ Nd / ¹⁴⁴ Nd, but ⁸⁷ Sr / ⁸⁶ Sr strongly scattering and very clearly increased, the latter ratio approaching the values of typical upper crustal rocks in the Mediterranean region. In general, the isotope ratios of Verite and Verite are very independent, but an approximation of Shoshonite and Lamproite in Tuscany and lamproic minettes in the western Alps can be observed for both parameters . In contrast to the madupites and orendites , which belong to the association of the interior of the plate, verites follow a flat trend of orogenetically influenced association. In comparison with the other lamproites in southeastern Spain, their ⁸⁷ Sr / ⁸⁶ Sr values are significantly higher than those of the Jumillite (J), Fortunite (F) and Cancalite , which means that they are significantly more heavily contaminated with crustals.

With the very high, little variable lead ratios, which overlap with the values for oceanic sediments, there are also similarities with lamproites of Tuscany and lamproic minets of the western Alps. In comparison with the other magma provinces of the Mediterranean area, however, the lead ratios of the verites, which are put in relation, show an opposite, negatively correlated trend.

Age

The Verit was dated to 6.37 million years BP and thus comes from the late Miocene ( Messinian ).

Individual evidence

^ Osann, CA: Contributions to the knowledge of the igneous rocks of Cabo de Gata (Prov. Almeria) . In: Journal of the German Geological Society . Vol. 41. Berlin 1889, p. 297-311 .
↑ Mitchell, RH and Bergman, SC: Petrology of lamproites . Plenum Press, New York, New York 1991.
↑ ^a ^b Conticelli, S. et al .: Trace elements and Sr-Nd-Pb isotopes of K-rich, shoshonitic and calc-alkaline magmatism of the Western Mediterranean Region: Genesis of ultrapotassic to calc-alkaline magmatic associations in a post-collisional geodynamic setting . In: Lithos . tape 107 , 2009, p. 68-92 , doi : 10.1016 / j.lithos.2008.07.016 .
↑ Benito, R. et al.: Sr and O constraints on source and crustal contamination in the high-K calc-alkaline and shoshonitic neogene volcanic rocks of SE Spain . In: Lithos . tape 46 , 1999, pp. 773-802 .

[1] Osann, CA: Contributions to the knowledge of the igneous rocks of Cabo de Gata (Prov. Almeria) . In: Journal of the German Geological Society . Vol. 41. Berlin 1889, p. 297-311 .

[2] Mitchell, RH and Bergman, SC: Petrology of lamproites . Plenum Press, New York, New York 1991.

[Conticelli-3] Conticelli, S. et al .: Trace elements and Sr-Nd-Pb isotopes of K-rich, shoshonitic and calc-alkaline magmatism of the Western Mediterranean Region: Genesis of ultrapotassic to calc-alkaline magmatic associations in a post-collisional geodynamic setting . In: Lithos . tape 107 , 2009, p. 68-92 , doi : 10.1016 / j.lithos.2008.07.016 .

[4] Benito, R. et al.: Sr and O constraints on source and crustal contamination in the high-K calc-alkaline and shoshonitic neogene volcanic rocks of SE Spain . In: Lithos . tape 46 , 1999, pp. 773-802 .