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The Geochemical Characteristics And Geological Significance Of The Intrusive Rocks In The North Of Ailaoshan Tection Zone

Posted on:2016-09-15Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhengFull Text:PDF
GTID:2180330461455579Subject:Mineralogy, petrology, ore deposits
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The Ailaoshan tection zone is an important structural transformation belt that is distributed as NW to SE, which has experienced the Tethys evolution from the late Neopaleozoic to the collision of india with the eurasian plate in Cenozoic. There are three regional deep faults(left to right the Red River fault, Ailaoshan fault and Amojiang fault) in the Ailaoshan tection belt. When the faults in Ailaoshan tection belt is active, intrusive rocks would invade in the belt. This paper is based on the theory of tection and magma to research the petrological characteristics, the chemical characteristics of studying region’s intrusive rock.The intrusive rock are mainly distributed in the internal and two sides of the Ailaoshan tection zone. Based on the result of the SHRIMP zircon U-Pb dating, we found the age of intrusive rock in the studying area are the Himalayan epoch and Indo-Chinese epoch, the number of the Himalayan epoch’s intrusive rock is four and the number of Indo-Chinese epoch’s intrusive rock is 2. The age of the Himalayan epoch’s intrusive rock is 33~35Ma and the age of Indo-Chinese epoch’s intrusive rock is 194~234Ma. Azhalu rock can be regarded as two intruded period by studying them in the wild and thin section identification in the room.The intrusive rock of first period is Indo-Chinese epoch which is judged by SHRIMP zircon U-Pb dating. The intrusive rock of second period is Himalayan epoch which is judged by studying them in the wild, thin section identification indoor and comparing with other Himalayan epoch’s intrusive rock.Intrusive rocks in study area are all neutral-acid intrusive rocks. Lupanglang rock are flesh red biotite quartz diorite porphyrite, purple gray biotite quartz diorite porphyrite et al, they are all belongs to hypabyssal diorite porphyrite.Jiucun rock are grey granitic mylonite, mylonitized granite, initial granitic mylonite, granitic gneiss et al, which are experienced dynamic metamorphism. Azhalu first period rock are mylonitized granite, sencond period rock are alkali feldspar muscovite granite porphyry.Aqiuhe rock are monzonitic granite and k-feldspar granite.Tuantianshan rock biotite quartz syenite and biotite quartz monzonite.The Himalayan epoch rock in study area belong to Ailaoshan-Red river fault potassic alkali plutons zone. Its chemical characteristics are: Samples of SiO2 with an average of 72.28% which belong to acidic rocks, According to the analysis of geochemical characteristics of the alkali-peraluminous excessive series, the characteristics of trace and rare earth elements are the enrichment of Ba, K which are large ion lithophile element(LILE), Loss of Ta, Nb, P, Ti which are high field strength element(HFSE). REE fractionation, Belong to the LREE enrichment type. Eu with a slight negative anomaly. The Indo-Chinese epoch rock in study are: The SiO2 content of the sample mean value is 62.23% which belong to acidic rocks and peraluminous series. Na2 O is greater than K2 O, the rock is alkalic series. Th, U, Pb and enrichment of trace elements, loss of Ba, Ta, Nb, P, Ti etc. The overall performance of the ion lithophile element(LILE) changes a lot, Large ion lithophile element did not change significantly. Fractionation of rare earth elements which belong to the light rare earth enrichment type. The average value of 0.75 δEu, Eu with a slight negative anomaly, Show no residual plagioclase rock formation did not occur in plagioclase crystallization separation of partial melting of the source region.The Himalayan epoch rock in study area belong to A type granite, Silicon aluminum layer of magma may be derived from the crust. Originated in the source region of relatively shallow, The ascent of magma in the process did not significantly affected by assimilation and fractional crystallization. Its tectonic setting in late orogenic extension environment- post orogenic. The Indo-Chinese epoch rock in study belong to S type granite, the magma originated from the shallow source area, Received a slight contamination of mantle derived magmas during magma ascent and emplacement. Tectonic background for the same collision serorogenic granite.
Keywords/Search Tags:the Ailaoshan tection zone, the intrusive rocks, geochemical characteristics, zircon U-Pb dating, Yunnan
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