Orendit
The orendite is a quite rare igneous rock that is counted among the lamproites . The rock, which comes from the upper mantle , is characterized by its ultrapotassic character.
Type locality and first description
The Orendit is named after its type locality , the Orenda Butte (or Orenda Mesa , more recently Spring Butte ) belonging to the Leucite Hills in Wyoming . The rock was first scientifically described by Charles Whitman Cross in 1897 .
definition
The Orendit is now defined as Diopside-Sanidin-Phlogopit-Lamproit. Originally, the rock name was still used for a variety of leucite phonolite , which was composed of leucite and alkali feldspar and subordinate clinopyroxene , mica and amphibole .
Petrology
mineralogy
According to the redefinition, orendite have phlogopite as characteristic phenocrystals . Sanidine and diopside do not form phenocrystals, but are found in the matrix alongside leucite , with diopside being enclosed by sanidine. However, olivine (especially in olivine orendites) acts as a further phenocrystal , which can be resorbed. Apatite , magnophorite , priderite and partly resorbed Richterite also occur as accessories . In glassy varieties, these are hornblende ( pargasite ) and magnetite . Chromite , ilmenite , rutile and zircon are also rarely present. Calcite can appear as a secondary mineral .
Chemical composition
The following rock analyzes should clarify the chemical composition of the return:
| Oxide wt.% |
Orendit | Orciatico-Orendit | Olivine orenditol | Emmons Cone Leucite Hills |
|---|---|---|---|---|
| SiO 2 | 55.14 | 56.74 | 53.07 | 52.64 |
| TiO 2 | 2.58 | 1.42 | 2.41 | 1.72 |
| Al 2 O 3 | 10.35 | 11.25 | 8.96 | 13.38 |
| Fe 2 O 3 | 3.27 | 2.00 | 3.86 | 5.19 |
| FeO | 0.62 | 2.92 | 0.91 | 1.63 |
| MnO | 0.06 | 0.08 | 0.08 | 0.09 |
| MgO | 6.41 | 8.29 | 11.17 | 4.40 |
| CaO | 3.45 | 4.40 | 3.56 | 3.16 |
| Na 2 O | 1.21 | 1.36 | 1.15 | 2.22 |
| K 2 O | 11.77 | 7.68 | 10.72 | 11.96 |
| P 2 O 5 | 1.40 | 0.70 | 1.24 | 0.44 |
| LOI | 1.84 | 3.16 | 1.56 | 2.31 |
Occurrence
- Italy :
-
Turkey :
- Afyon Stratovolcano near Afyon , Western Anatolia
-
United States of America :
-
Wyoming - Leucite Hills
- Emmons Cone
- North Table Mountain
- Orenda Butte (type locality)
- South Table Mountain
-
Wyoming - Leucite Hills
Individual evidence
- ↑ Cross, CW: Art. XVI - Igneous rocks of the Leucite Hills and Pilot Butte, Wyoming . In: American Journal of Science . Vol. 4, 4th Series. New Haven 1897, p. 115-141 .
- ↑ Mitchell, RH and Bergman, SC: Petrology of Lamproites . Springer Science & Business Media, 1991, ISBN 978-1-4613-6688-1 , doi : 10.1007 / 978-1-4615-3788-5 .
- ↑ Aydar, E., Bayhan, H. and Gourgaud, A .: The lamprophyres of Afyon stratovolcano, western Anatolia, Turkey: description and genesis . In: Comptes Rendus Geoscience . tape 335 , 2003, p. 279-288 , doi : 10.1016 / S1631-0713 (03) 0049-X .