File:Ankeritic carbonatite (Chilwa Alkaline Province, Early Cretaceous, 126 Ma; Chilwa Island, Lake Chilwa, Malawi, southeastern Africa) 1 (25833642803).jpg
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[edit]DescriptionAnkeritic carbonatite (Chilwa Alkaline Province, Early Cretaceous, 126 Ma; Chilwa Island, Lake Chilwa, Malawi, southeastern Africa) 1 (25833642803).jpg |
Ankeritic carbonatite from the Cretaceous of Malawi, Africa. (~6.8 cm across at its widest) Carbonatites are rare igneous rocks - they are composed of carbonate minerals, typically calcite (CaCO3 - calcium carbonate). Carbonatites are essentially igneous limestones. The four categories of carbonatites are: 1) calciocarbonatite (calcite-dominated) 2) magnesiocarbonatite (dolomite-dominated) 3) ferrocarbonatite (siderite-dominated) 4) natrocarbonatite (sodium carbonate-dominated) Calciocarbonatites are the most common type, whereas natrocarbonatites are extremely rare, which are only found at Ol Doinyo Lengai Volcano in eastern Africa. The carbonatite shown above is from the Early Creatceous-aged Chilwa Alkaline Province, an igneous complex consisting of intrusive igneous rocks (alkali granites, syenites, alkaline syenites, nephilinites, and carbonatites) and extrusive igneous rocks (lavas - basanites, phonolites). The complex was intruded in phases throughout the Early Cretaceous, from about 111 to 138 million years ago. The rock mildly effervesces in acid - it is dominated by the carbonate mineral ankerite, Ca(Fe,Mg,Mn)(CO3)2 - calcium iron magnesium manganese carbonate. The thin, dark reddish-brown vein cutting across the rock from left to right has calcite (it bubbles in acid very well). Geologic unit & age: Chilwa Alkaline Province, late Barremian Stage, mid-Early Creatceous, 126 Ma (= absolute date of Chilwa Island carbonatite) Locality: Chilwa Island, western Lake Chilwa, southeastern Malawi, southeastern Africa |
Date | |
Source | Ankeritic carbonatite (Chilwa Alkaline Province, Early Cretaceous, 126 Ma; Chilwa Island, Lake Chilwa, Malawi, southeastern Africa) 1 |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/25833642803 (archive). It was reviewed on 1 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
1 December 2019
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current | 08:58, 1 December 2019 | 3,060 × 2,023 (3.67 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Camera manufacturer | Canon |
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ISO speed rating | 80 |
Date and time of data generation | 22:54, 14 April 2016 |
Lens focal length | 7.23 mm |
Image title | |
Width | 4,000 px |
Height | 3,000 px |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 23:10, 14 April 2016 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 22:54, 14 April 2016 |
Meaning of each component |
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APEX shutter speed | 5.90625 |
APEX aperture | 6.34375 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 3.34375 APEX (f/3.19) |
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Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 17:10, 14 April 2016 |
Unique ID of original document | 19219FD3D8CAB543E16F11B1BFD3119F |
IIM version | 32,767 |