HR: 15:00h
AN: V43E-05 INVITED [Abstracts]
TI: Diamond and Unusual Minerals Discovered from the Chromitite in Polar Ural: A First Report
AU: * Yang, J
EM: yangjingsui@yahoo.com.cn
AF: Key Laboratory for Continental Dynamics, Institute of Geology, Chinese Academy of
Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China
AU: Bai, W
EM: yangjingsui@yahoo.com.cn
AF: Key Laboratory for Continental Dynamics, Institute of Geology, Chinese Academy of
Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China
AU: Fang, Q
EM: yangjingsui@yahoo.com.cn
AF: Key Laboratory for Continental Dynamics, Institute of Geology, Chinese Academy of
Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China
AU: Meng, F
EM: yangjingsui@yahoo.com.cn
AF: Key Laboratory for Continental Dynamics, Institute of Geology, Chinese Academy of
Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China
AU: Chen, S
EM: yangjingsui@yahoo.com.cn
AF: Key Laboratory for Continental Dynamics, Institute of Geology, Chinese Academy of
Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China
AU: Zhang, Z
EM: yangjingsui@yahoo.com.cn
AF: Key Laboratory for Continental Dynamics, Institute of Geology, Chinese Academy of
Geological Sciences, 26 Baiwanzhuang Road, Beijing, 100037, China
AB:
Ultrahigh pressure (UHP) minerals, such as diamond, coesite, and pseudomorphs of octahedral olivine, and as
well as about 80 other mineral species have been recovered from podiform chromitites of the Luobusa ophiolite,
southern Tibet, and a new mineral, Luobusaite (Fe0.82Si2), has been approved recently by CNMMN. The UHP
minerals from Luobusa are controversial because they have not found in situ and because ophiolites are
currently believed to form at shallow levels above oceanic spreading centers. More detailed study and
experimental work are needed to understand the origin and significance of these unusual minerals and
investigations of other ophiolites are needed to determine if such minerals occur elsewhere.
For this purpose, we collected about 1500 kg of chromitite from two orebodies in an ultramafic body in the Polar
Urals. Thus far, more than 60 different mineral species have been separated from these ores. The most exciting
discovery is the common occurrence of diamond, a typical UHP mineral in the Luobusa chromitites. Diamonds
from Ural chromitite are clear, colorless, well-developed crystals with octahedral morphology, generally 0.2-0.3
mm in size. Attached with the diamonds and perhaps also occurring as inclusions within them are many
minerals as chromite, MnNiCrFe alloy, native Si and Ta, corundum, zircon, feldspar, garnet, moissanite,
confirming their natural origin and suggesting a long residence time in the mantle.
Other mineral group include: (1) native elements: Cr, W, Ni, Co, Si, Al and Ta; (2) carbides: SiC and WC; (3) alloys:
Cr-Fe, Si-Al-Fe, Ni-Cu, Ag-Au, Ag-Sn, Fe-Si, Fe-P, and Ag-Zn-Sn; (4) oxides: NiCrFe, PbSn, REE, rutile and Si-
bearing rutile, ilmenite, corundum, chromite, MgO, and SnO2; (5) silicates: kyanite, pseudomorphs of octahedral
olivine, zircon, garnet, feldspar, and quartz,; (6) sulfides of Fe, Ni, Cu, Mo, Pb, Ab, AsFe, FeNi, CuZn, and CoFeNi;
and (7) iron groups: native Fe, FeO, and Fe2O3.
These minerals are very similar in composition and structure to those reported from the Luobusa chromitites.
For examples, some spherules of native iron contain spherical inclusions of FeO, exactly like comparable grains
in the Luobusa sample.
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 3613 Subduction zone processes (1031, 3060, 8170, 8413)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting