SHRIMP U-Pb Age,Hf Isotope Composition and Geochemical Characteristics of Neoarchean Granitic Complex in Liaodong Lianshanguan Area,NE China

Yang Fengchao; Sun Jinggui; Song Yunhong; Zhang Peng; Bi Zhongwei

doi:10.3799/dqkx.2016.140

Abstract：The fine chronology and geochemistry of the Lianshanguan granite complex in Benxi are scarce,and the Neoarchean mag-matism in the Liaodong area is less and the study is relatively weak.The Lianshanguan area at Benxi in East Liaoning is the favorable metallogenic area for endogenous uranium deposits within uranium concentration area.Uranium deposits near the contact zone with the region mainly occur in Lianshanguan granitic complex and Langzishan Formation of Liaohe Group or Anshan Group,indicating close relationship between the rock and uranium mineralization.In Lianshanguan area,light flesh red syenogranite yields an SHRIMP U-Pb age of 2 512±14 Ma,white streak-shape monzonitic granite yields an SHRIMP U-Pb age of 2 510±15 Ma,and emplacement age of granitic complex is Neoarchean.Syenogranites show SiO2 of 69.28%-72.70%,K2 O of 6.24%-7.12%,Na2 O of 2.77%-3.09%,Al2 O3 of 13.68%-15.92%.Monzonitic granites show SiO2 of 65.53%-71.01%,K2 O of 2.95%-3.90%,Na2 O of 3.57%-4.23%,Al2 O3 of 14.13%-14.90%.Lianshanguan granitic complex contains muscovite and shows 1.09-1.16 (average 1.12)of A/CNK,1.37-2.28 of corundum (C),no negative correlation between P2 O5 and SiO2 ,so it is characterized by high potas-sium S-type granite.rare earth elements show higher content,strong fractional distillation between light and heavy rare earth elements, from positive to negative Eu anomaly (δEu=3.55-0.36),loss of Nb,Ta,P,Ti high field strength elements,enrichment of Rb, Th,K and other large-ion lithophile elements.TheεHf(t)is-15.19 to-0.47,single-stage Hf model ages TDM are 2 826-3 400 Ma, and two-stage Hf model ages TDMC are 2 931-3 650 Ma.The Lianshanguan granitic complex in Liaodong area may be formed by deep-melting of Middle-Archean and Paleozoic crustal materials (mainly metamorphic mudstones and miscellaneous sandstones)under high-temperature and medium-pressure conditions,and may occur in the post-collision environment.It indicates that North China Craton micro-land collage was completed.