Rauhaugit

Rauhaugit is an igneous rock belonging to the rock group of carbonatites . Together with Beforsit it belongs to the dolomite carbonatites , as its modal mineral composition is dominated by dolomite .

Etymology and type locality

The rock name Rauhaugit comes from its type locality , the village of Rauhaug ( Telemark , Norway ) in the Fen complex .

Initial description

Rauhaugit was scientifically described for the first time in 1921 by Waldemar Christofer Brøgger .

Outward appearance

Rauhaugite are very light to white rocks that weather light brown.

mineralogy

The main mineral in rauhaugite is by definition dolomite, which is represented with more than 50 percent by volume. Anchorite or dolomitic anchorite can also be found in dolomite, which is sometimes rich in iron . Other carbonates are calcite , magnesite , siderite and magnesium- rich siderite. Chlorite (as an alteration mineral), biotite , quartz , apatite and barite act as accompanying minerals . Accessories are pyrochlore (also rich in uranium ), columbite , monazite , zirconium , phlogopite , amphibole ( e.g. magnesium-rich arfvedsonite ) and niacolite .

Petrology

Rough-haugite can be viewed as a slightly finer-grain version of Beforsite. Nevertheless, it also forms coarse-grained to very coarse-grained, mono- mineral cumulative structures . In addition, it can develop a porphyry texture - with sometimes very large porphyroclasts that can reach up to 50 millimeters. It also shows a mixed structure with silicate minerals .

Due to their high magnesium content (up to 18.8 percent by weight MgO), Rauhaugites represent primitive carbonatite melts that come more or less unchanged directly from the earth's mantle . The formation of rauhaugite was also interpreted as an immiscible enamel fraction of a damkjernite magma ( lamprophyr variety). Tectonically stressed rough haugites can reveal twisted twin lamellae and undissolved extinction of the carbonate minerals under the polarization microscope .

Occurrence

• Angola :
  • Bonga ( Benguela )
• Australia :
  • Mount Weld , Western Australia - 2060 million years BP
• People's Republic of China :
  • Bayan obo
• Greenland :
  • Safartoq
• Canada :
  • British Columbia :
    • Aley
  • Ontario :
    • Firesand River at Wawa
• India :
  • Newania , Rajasthan - Proterozoic
• Norway :
  • Fen complex in Telemark (type locality)
• Zambia :
  • Nkombwa Hill
• Zaire :
  • Kirumba , Kivu

Individual evidence

1. ^ WC Brögger: The igneous rocks of the Kristianiag region. IV. The Fen area in Telemark, Norway. In: Skrifter udgift av Videnskabsselskabet i Kristiania. I. Math.-Nat. Class . No. 9 , 1921, pp. 1-408 .
2. ↑ K. Secher, LM Larsen: Geology and mineralogy of the Safartoq carbonatite complex, southern West Greenland . In: Lithos . tape 13 , 1980, pp. 199-212 .
3. ↑ SG Viladkar, I. Ghose: U-rich pyrochlore in carbonatites of Newania, Rajasthan . In: N. Jb. Miner. Mh. Year 2002 (3), 2002, p. 97-106 .