Dolerite
A rock subtype
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About Dolerite
Name:
Etymol: Greek doleros, 'deceitful,' in reference to the fine-grained character of the rock that makes it difficult to identify megascopically.
Dolerite and the synonym diabase are not root names but usually defined as medium grained (1 to 5 mm) mafic intrusive rocks. It can include microgabbro, basalt, andesite, microdiorite and other rock types. They can contain coarse grained zones which can be termed gabbro or granophyre.
i. In the United States, a synonym of diabase
Ref: AGI
ii. In British and Australian usage: A medium grained mafic intrusive rock whose main components are calcic plagioclase and clinopyroxene and which is characterized by ophitic to subophitic texture; usually found in sills and dykes. The preferred term for what is called diabase in the United States. Of similar mineralogy to basalt and gabbro, and intermediate in grain size between them.
Compare with: diorite, trap.
i. In the United States, a synonym of diabase
Ref: AGI
ii. In British and Australian usage: A medium grained mafic intrusive rock whose main components are calcic plagioclase and clinopyroxene and which is characterized by ophitic to subophitic texture; usually found in sills and dykes. The preferred term for what is called diabase in the United States. Of similar mineralogy to basalt and gabbro, and intermediate in grain size between them.
Compare with: diorite, trap.
Unique Identifiers
Mindat ID:
48432
Long-form identifier:
mindat:1:1:48432:3
Similar Names
| Dolereid | A rock subtype |
| Dolerine | A rock subtype |
| Doleroid | A synonym of 'Foid-bearing dolerite' |
| Doverite | A synonym of Synchysite-(Y) |
Classification of Dolerite
Sub-divisions of Dolerite
Mineralogy of Dolerite
Essential minerals - these are minerals that are required within the classification of this rock:
| Feldspar > Plagioclase | (Na,Ca)[(Si,Al)AlSi2]O8 |
| Pyroxene | A petrological term for Pyroxene Group. |
Non-essential minerals - these minerals are common, sometimes major components, but are not always present:
| Amphibole > Hornblende | AnCa2(Z2+5-mZ3+m)(Si8-(n+m)Al(n+m))(OH,F,Cl)2 |
| Feldspar > Alkali Feldspar > K Feldspar | Potassium-dominant feldspars with variable crystal symmetry and Al-Si ordering state; they are a subgroup of ... |
| Silica > Quartz | SiO2 |
Age distribution
Recorded ages:
Phanerozoic : 219 ± 6 Ma to 6.53 ± 0.26 Ma - based on 6 recorded ages.
Sample ages:
| Sample ID | Recorded age | Geologic Time | Dating method |
|---|---|---|---|
| 1 | 6.53 ± 0.26 Ma | Miocene | K-Ar |
| 2 | 32.0 ± 1 Ma | Oligocene | K-Ar whole rock |
| 3 | 86.3 ± 2.0 Ma | Late/Upper Cretaceous | 40Ar-39Ar |
| 4 | 88 Ma | Late/Upper Cretaceous | K-Ar |
Sample references:
| ID | Locality | Reference | Notes |
|---|---|---|---|
| 1 | Inaccessible Island, Tristan da Cunha Archipelago, Saint Helena, Ascension and Tristan da Cunha | ||
| 2 | Jebel Uweinat, Kufra District, Libya | dolerite cutting the Uweinat granite | |
| 3 | Androy Volcanic Complex, Madagascar | ||
| 4 | Nemuro peninsula occurrence, Nemuro City, Nemuro Subprefecture, Hokkaidō Prefecture, Japan | Six K-Ar dated samples of the least altered of an undifferentiated dolerite sheets |
Synonyms of Dolerite
Common Associates
Associations Based on Photo Data:
| 10 photos of Dolerite associated with Calcite | CaCO3 |
| 8 photos of Dolerite associated with Prehnite | Ca2Al2Si3O10(OH)2 |
| 8 photos of Dolerite associated with Pectolite | NaCa2Si3O8(OH) |
| 6 photos of Dolerite associated with Quartz | SiO2 |
| 4 photos of Dolerite associated with Augite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
| 3 photos of Dolerite associated with Aerinite | (Ca5.1Na0.5)(Fe3+,Al,Fe2+,Mg)4(Al,Mg)6[HSi12O36(OH)12][(CO3)1.2(H2O)12] |
| 2 photos of Dolerite associated with Plagioclase | (Na,Ca)[(Si,Al)AlSi2]O8 |
| 2 photos of Dolerite associated with Celadonite | K(MgFe3+◻)(Si4O10)(OH)2 |
| 1 photo of Dolerite associated with 'Porphyry' | |
| 1 photo of Dolerite associated with Chlorite Group |
Internet Links for Dolerite
mindat.org URL:
https://www.mindat.org/min-48432.html
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References for Dolerite
Reference List:
Haslestad Quarry, Hof, Holmestrand, Vestfold, Norway