Jumillit

The jumillite is a very rare ultrapotassic magmatite that is counted among the lamproites , more precisely to the madupite lamproites . It forms part of the southeast Iberian volcanic province .

First description and occurrence

The Jumillit was scientifically described for the first time in 1906 by Carl Alfred Osann . The type locality , after which the rock was named, is in the Murcia region in southeastern Spain, around 10 kilometers west of Jumilla on the RD 428 road to Hellín .

Petrology

Entrance to the La Mina-Caserio de La Celia mine , type locality des Jumillits

Osann originally described the jumillite as a variety of an olivine-bearing phonolithic leucitite , which mainly consisted of leucite and diopside , to which olivine , alkali feldspar and phlogopite were added. According to the new Lamproit classification, the rock is now referred to as Olivine-Diopside-Richterite-Madupit-Lamproit .

The jumillite is a brown, gray to dark green, in its interior massive lava rock , which is present as scoria at its type locality, the former volcano La Celia . It shows intense surface weathering.

Quite rare warwickite from the Nuestra señora del Carmen mine near La Celia, Jumilla

Mineral inventory

Mineralogically, olivine ( Forsterite Fo _86-88 ) and titanium-rich phlogopite can be recognized as phenocrystals in jumillite . The vitreous base mass contains diopside, sanidine , richterite , orthopyroxene , leucite , akmit , apatite and, as opaque minerals, hematite , ilmenite , picotite and hercynite . In secondary carbonate veins associated with the lamproite rock , besides calcite and gypsum, warwickite and very rare fine-rayed needles of yuanfuliite can be found. In the Nuestra señora del Carmen mine there are also analcime , augite , fluorapatite , fluor Richterite, hydroxyapatite , pseudobrookite , tridymite and wadeit .

Petrography

First crystallizates in jumillite are olivine, phlogopite, diopside and leucite, all of which are poikilitically enclosed by the last crystallizing sanidine . The idiomorphic olivine, which has a grain size of up to 2 millimeters , shows signs of transformation to iron oxides and serpentinization at the edges . The light green, chromium-containing diopside occurs in two generations, a coarse-grained (up to 1.5 millimeter grain size) first and a fine-grained second generation, which crystallizes as small slats and panels. The pleochroic phlogopite occasionally shows twin lamellae , but characteristic is its screen structure ( Engl. Sieve structure ) and its poikilitische enclosure of leucite, apatite and small Diopsidtafeln the second generation. It can be absorbed by iron oxides. The leucite is glomerophyric and is associated with Richterite.

Yuanfuliite

Chemical composition

Main elements

Oxide wt.%	Jumillit bandwidth	Jumillit 11A8	Jumillit	Jumillit La Celia	Jumillit SP 452	Jumillit SP 055
SiO 2	45.53-51.52	47.31	48.99	49.90	50.3	52.7
TiO 2	1.28-1.66	1.32	1.54	1.48	1.35	1.34
Al 2 O 3	6.40-9.77	6.52	8.45	9.77	8.80	9.53
Fe 2 O 3	1.45-3.94	3.83	3.94	5.43 (dead)	6.12 (dead)	5.36 (dead)
FeO	1.98-4.31	2.88	1.98
MnO	0.01-0.12	0.12	0.09	0.10	0.01	0.03
MgO	11.90-17.37	17.16	16.68	11.90	14.5	13.1
CaO	4.14-9.06	8.82	7.65	6.16	5.94	4.87
Na 2 O	0.92-2.20	1.88	1.13	0.92	1.09	1.75
K 2 O	3.6- 7.39	3.71	6.86	5.33	7.04	6.97
P 2 O 5	1.16-2.04	2.00	1.25	1.60	1.62	1.15
LOI	1.78-4.81	5.08	1.78	4.81	2.51	2.63
Mg #	0.85-0.94		0.94		0.85	0.85
K / Na	2.21-4.24	1.30	4.00	3.82	4.24	2.62
K / Al	0.59-0.88	0.62	0.88	0.59	0.87	0.79
(Na + K) / Al	0.75-1.22	1.09	1.10	0.75	1.07	1.09

The mesocratic jumillite is a mafic , predominantly peralkaline (with (Na + K) / Al> 1) and potassic to ultrapotasic (with K / Na> 3) rock and thus belongs to the alkali rocks with a predominance of potassium . It is characterized by an extremely high MgO content of 13 to 17 percent by weight. In addition, CaO is significantly enriched with up to 9 and P ₂ O ₅ with up to 2 percent by weight. Al ₂ O ₃ with 6 to 9 and Na ₂ O below 2 percent by weight are low.

As standard minerals appear next to orthoclase ( Or ) with 21.90 volume percent and albite ( Ab ) with 12.42 volume percent, olivine ( Ol ) with 22.8 volume percent, Akmit ( Ac ) with 2.68 volume percent and nepheline ( Ne ) with 0, 23 percent by volume. Akmit and nepheline as well as the lack of quartz show the undersaturated silicon character of the rock. Further standard minerals are diopside ( Di ) with 24.07 volume percent, magnetite ( Mt ) with 4.20 volume percent, ilmenite ( Il ) with 2.51 volume percent and apatite ( Ap ) with 4.70 volume percent.

The pereralcalinity is indicated by the modal occurrence of Richterite and Akmit.

Trace elements

Trace elements ppm	Jumillit bandwidth	Jumillit La Celia	Jumillit SP452	Jumillit SP 055
Cr	908-1170	1170	908	941
Ni	340-558	340	558	464
Zn	69.8-104	98.0	104	69.8
Rb	253-736	253	322	736
Sr	842-1617	1375	1617	842
Zr	628-749	628	749	671
Ba	2593-3776	3216	3776	2593
Ce	223-272	263	272	223
Nd	146-167	163	167	146
Sm	27.9-31.1	31.1	32.0	27.9
Hf	18.7-20.6	20.6	19.2	18.7
Th	91.2-114	114	114	91.2

In terms of trace elements, jumillite is significantly enriched in incompatible elements , especially LILE elements such as cesium or strontium and HFSE elements such as zirconium , thorium , uranium , lead and terbium have increased values. In the spider diagram, there are negative spikes for barium with moderate concentrations, niobium and titanium . Overall, the curve is almost congruent with the lamproites of Tuscany and the lamproite- like minettes of the Italian western Alps .

Isotope ratios

Neodymium-strontium isotope diagram with the position of the Jumillite (J) compared to other lamproites

Isotopes	Jumillit La Celia	Jumillit SP 452	Jumillit SP 055
87 Sr / 86 Sr	0.717191	0.716415	0.716666
143 Nd / 144 Nd	0.512175	0.512460	0.512014
206 Pb / 204 Pb	18.777	18.783
207 Pb / 204 Pb	15.682	15,705
208 Pb / 204 Pb	39.007	39.090

In the isotope ratios ¹⁴³ Nd / ¹⁴⁴ Nd is relatively low, but ⁸⁷ Sr / ⁸⁶ Sr is increased and tends towards the values ​​of upper crustal rocks ; Compared to the other lamproites of southeastern Spain such as Fortunit (F), Cancalit (C) and Verit (V), however, the jumillites are the least contaminated by the crustal components. In contrast to the madupites and orendites , which belong to the association of the interior of the plate, they follow a flat trend of orogenetically influenced association. Again, these two parameters are almost identical to the conditions in Tuscany and the Western Alps. The lead ratios, which overlap with the values ​​for oceanic sediments, are also in agreement with Tuscany. The quite high ²⁰⁸ Pb / ²⁰⁴ Pb ratio is also striking .

Age

The jumillite of the type locality was dated in 2005 by Duggen and colleagues to be 6.76 ± 0.04 million years BP . It was therefore formed in the Messinium .

Economical meaning

Because of the abundant apatite, the jumillite was mined in two mines on phosphorus for fertilizer production during the 19th and 20th centuries .

Individual evidence

1. ↑ Osann, CA: About some alkaline rocks from Spain . Ed .: Wülfing, EA, Festschrift Harry Rosenbusch. Swiss beard, Stuttgart 1906, p. 263-310 .
2. ↑ Mitchell, RH and Bergman, SC: Petrology of lamproites . Plenum Press, New York, New York 1991.
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 .
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 .