The Petrochemical Feactures and Rb-Nb-Y Potential of the Xiaojiang Granitic Intrusion,Guidong,Hunan
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Rb is an important rare metal element used widely in industry.Placer Sn was explored in the Xiaojiang region in Guidong,Hunan in 1958,but no follow-up work has been reported.Samples were collected from the fine-grained two-mica granite,the biotite porphyritic granite,and the coarse grained biotite granite in the Xiaojiang ore field.The petrochemical features of the samples show that the three types of granites were likely originated from the same granitic magma.Due to fractional crystallization of the granitic magma,the latest fine-grained two-mica granite is enriched in rare metals and Y with tetrad REE pattern.For example,in the two-mica granite,Rb2O(0.10%),Nb2O5(0.005%),and Y2O3(0.01%) contents are beyond or around the cutoff grades.The EMPA analysis shows that Rb is enriched in K-feldspar and biotite,while Y is enriched in fluorite.In the end,the reserves of Rb2O is estimated to be about 320,000 tons assuming the Rb mineralization depth of the Xiaojiang granite is 50 m,and granite has a promising perspective for pegmatite type rare metal deposit and ion adsorption type REE deposit as well.Keywords:
Porphyritic
EMPA
Greisen
Pegmatite
Fractional crystallization (geology)
Tourmaline
Fluorite
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Furong super-unit is a part of Qitianling granite mass which is Yanshanian complex pluton,and is mainly composed of adamellite and moyite.K2O+Na2O in content ranges from 7.32% to 10.01%,the average is 8.17%.In the granitic classification diagram of K2O-Na2O,the most samples are plotted in the area of A-type granite,but they are characterized by high TiO2,CaO,MgO,and lower FeO*/MgO contrasted with the typical A-type granite.The REE distribution patterns of granite are similar to each other,and show typical LREE enrichment,an obvious negative Eu anomaly pattern.The LREE distribution curves are light right deviation and the part of HREE almost smooth.For the trace elements of granite,Rb and Th are enriched strongly,Sr and Ti appear as strong depletion,and Ba,Ta,Nb,Nd,Zr and Hf also show a character of enrichment in a certain degree.Qitianling granite with high tin background content is favorable to tin mineralization in space environment and time stage,showing a good potential to tin mineralization.
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Porphyritic
Fractional crystallization (geology)
Igneous differentiation
Trace element
Petrogenesis
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The Hardat Tolgoi Pb-Zn deposit is a medium-sized Pb-Zn deposit recently found in Erenhot-Dongwuqi polymetallic ore belt along the suture zone between the North China plate and the Siberia plate.The granite relevant to the Pb-Zn mineralization in the orefield is a concealed pluton.The LA-ICP-MS zircon U-Pb dating indicates that the granite was emplaced at 125±4.3 Ma and thus was the products ofYanshanianmagmatism.Detailed geochemical data show that the granite is composed of weakly peraluminous(A/CNK= 0.99-1.08) rocks with low iron,high silicon,and high alkali contents(mostly NaK).The granite is enriched in large-ion lithophile elements(LILEs,such as Rb and K),Nd and Ta,but is depleted in high-field strength elements(HFSEs,such as Nb and Ti),Ba and Sr.The chondrite-normalized REE pattern shows M type with tetrad effect and strong Eu depletion(δEu=0.003~0.013).These results suggest that the alkaline feldspar granite belongs to alkalinity A type granite and was formed in a post-orogenic tectonic environment.Nd-Pb isotopic compositions show that the alkaline feldspar granite was derived from partial melting of the Mesoproterozoic upper crust.
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Allanite
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Batholith
Columbite
Amphibole
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Petrogenesis
Pegmatite
Muscovite
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Fractional crystallization (geology)
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Kafang deposit is located in the Southeast of Gejiu ore field.The granite of the deposit is the mineralization rock.Anciently,the granite was also named by different researchers as biotite granite,biotite-monzogranite or biotite plagioclase granite and so on.However,microscope and electron microprobe analysis of the granite show that all the feldspars are K-feldspar and albite(An≤5),suggesting that the granite should be named as alkali feldspar granite.This kind of granite is usually formed from rich-volatile(Li-F) magma,with the extensive development of liquid immiscibility at the top of it.The effect of liquid immiscibility is the main differentiation way for forming the Sn-polymetallic deposit.The albite’s An value could be used as an indicator for evaluating granite in searching for Sn polymetallic mieralization.
Alkali feldspar
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Pegmatite
Batholith
Muscovite
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Fractional crystallization (geology)
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