膠東地區(qū)中生代中基性巖墻地球化學研究
發(fā)布時間：2018-08-22 15:54
【摘要】：中國東部顯生宙以來發(fā)生了多次重大的地質(zhì)事件,如華北克拉通的破壞,揚子板塊與華北克拉通的拼合,古太平洋板塊的俯沖。與此同時,巖漿作用在中國東部廣泛發(fā)育,尤其是中生代時期。這些巖漿巖的源區(qū)性質(zhì)、成巖過程及其地球化學動力學背景對于理解中國東部中生代巖石圈地幔的屬性及其演化提供了重要的制約。膠東半島位于中國中央造山帶(秦嶺-大別-蘇魯造山帶)的東部,東臨渤海灣,北接華北克拉通,南部毗鄰蘇魯造山帶,是研究深部巖石圈地幔組成和演化的天然實驗室。本文以膠東半島玲瓏地區(qū)和乳山地區(qū)早白堊世中基性巖墻為研究對象,分別進行了詳細的巖相學、鋯石U-Pb年齡、全巖主微量元素以及Sr-Nd-Pb放射性成因同位素分析,通過結(jié)合整個山東省中生代幔源侵入巖與火山巖數(shù)據(jù),進一步探討研究區(qū)中生代巖石圈地幔的組成特征。玲瓏地區(qū)屬于膠北地體,位于膠東半島北部,是華北克拉通的一部分。中基性巖墻的主要巖石類型為輝綠巖、煌斑巖和閃長玢巖。LA-ICPMS鋯石U-Pb定年結(jié)果顯示,其形成時代為121.3 ± 3.8～123.5 ± 4.6 Ma。它們具有較低的SiO2(44.53～55.05wt.%)和較高的MgO(6.77～13.26wt%,Mg#= 64～73)含量;高的K2O(1.5～4.4wt.%)含量,高Cr(383～818ppm)、Ni(135～328ppm)含量以及高的K20/Na2O比值(0.60～1.82)。在硅堿圖(TAS)上主要落入輝長巖范圍內(nèi)。乳山地區(qū)位于膠東半島南部的蘇魯造山帶內(nèi),是大陸碰撞造山帶的一部分�；詭r墻以閃長玢巖為主,LA-ICPMS鋯石U-Pb定年結(jié)果表明,其形成時代為107.6±1.6～118.2±3.3Ma。與玲瓏地區(qū)相比,乳山地區(qū)的樣品具有較大變化范圍的SiO2(45.54～60.66 wt.%)和 MgO(3.15～12.73 wt.%,Mg#= 58～76)含量。它們具有高K20(1.3～4.4 wt.%)含量,高 Cr(108～1176 ppm)、Ni(18.5～313 ppm)含量以及高的K2O/Na2O(0.47～1.71)比值。在硅堿圖(TAS)上主要落入正長閃長巖、閃長巖范圍內(nèi)。在微量元素和稀土元素配分圖上,兩個地區(qū)的中基性巖墻都富集大離子親石元素(LILE)和輕稀土元素(LREE),虧損高場強元素(HFSE)和重稀土元素(HREE),表現(xiàn)出明顯的"弧型"微量元素分配特征。玲瓏地區(qū)中基性巖墻具有較高的全巖初始87Sr/86Sr(0.7092～0.7112)、較低的εNd(t)值(-12.3～-19.6)和初始206Pb/204Pb(17.23～17.53),207Pb/204Pb(15.50～15.57),208Pb/204Pb(37.77～38.18)。與玲瓏地區(qū)相比,乳山地區(qū)樣品具有略低的初始87Sr/86Sr(0.7075～0.7094)、低放射性成因εNd(t)值(-10.9～-15.7)和較低的初始206Pb/204Pb(16.74～17.32),207Pb/204Pb(15.36～15.46),208Pb/204Pb(36.89～37.63)。這些地球化學特征表明,膠東地區(qū)的中基性巖墻起源于富集地幔。較低的TiO2和(Fe2O3)T含量表明它們的源區(qū)是巖石圈地幔而不是軟流圈地幔。在Sr-Nd-Pb同位素表現(xiàn)為更接近于華北克拉通巖石圈地幔,而遠離揚子克拉通巖石圈地幔。同時,初始87Sr/86Sr比值和初始εNd(t)值并不隨Mg#值的變化而變化,表明其在上升過程中受到的地殼混染作用不顯著,暗示著這些具有"弧型"微量元素分配特征的膠東中基性巖墻的巖漿源區(qū)為受到了交代作用的華北巖石圈地幔。另外,全巖Nb/U、Ce/Pb比值指示地幔源區(qū)有上地殼物質(zhì)的貢獻,其兩階段全巖Nd模式年齡與蘇魯造山帶超高壓變質(zhì)巖一致。綜合以上地球化學特點表明膠東地區(qū)中基性巖墻的地幔源區(qū)受到了揚子陸殼物質(zhì)的改造。從山東省中生代幔源中基性巖漿作用整體來看,研究區(qū)的中基性巖墻地球化學特征與靠近蘇魯造山帶的沂南輝長巖、方城玄武巖和膠萊盆地基性火山巖比較接近,而與華北克拉通內(nèi)部濟南鄒平地區(qū)的基性巖有明顯的差異。前者具有EM2型的富集特征而后者顯示EM1型的富集特征。我們認為揚子板塊的俯沖作用是兩者差異的主要原因,靠近蘇魯造山帶的膠東地區(qū)以及魯西東部地區(qū)受到俯沖交代作用較大,遠離造山帶的華北克拉通內(nèi)部受到俯沖交代作用較小。然而,從時代上來看大規(guī)模的巖漿作用形成在早白堊世,比揚子板塊俯沖/碰撞作用晚約90 Ma,暗示這次造山事件與膠東地區(qū)的巖石圈地幔的熔融存在明顯的時代差異。魯西地區(qū)中生代的幔源巖漿主要集中于185～177 Ma(軟流圈起源)和144～101 Ma(巖石圈起源),而膠東地區(qū)的幔源巖漿主要集中于134～102 Ma(巖石圈起源)和95～73 Ma(軟流圈起源),這樣的年齡分布特征與古太平洋板塊的俯沖/后撤作用一致,在古太平洋平板俯沖、后撤作用下,中國東部從擠壓背景轉(zhuǎn)變?yōu)槔瓘埍尘?減壓部分熔融是山東省早白堊世幔源巖漿作用的主要機制。
[Abstract]:Since the Phanerozoic, many important geological events have taken place in eastern China, such as the destruction of the North China Craton, the convergence of the Yangtze plate and the North China Craton, and the subduction of the Paleo-Pacific Plate. The Jiaodong Peninsula is located in the eastern part of China's Central Orogenic Belt (Qinling-Dabie-Sulu orogenic belt), east of Bohai Bay, north of North China craton, south of Sulu orogenic belt. It is a study of deep lithospheric mantle composition and evolution. Natural Laboratory of Chemistry. In this paper, the early Cretaceous intermediate-basic dykes in Linglong and Rushan areas of the Jiaodong Peninsula are studied. Detailed petrography, zircon U-Pb age, major trace elements and Sr-Nd-Pb radiogenic isotope analysis of the whole rock are carried out. The data of Mesozoic mantle-derived intrusive rocks and volcanic rocks in Shandong Province are combined. Linglong area belongs to Jiaobei terrane, located in the northern part of Jiaodong Peninsula, and is a part of the North China Craton. The main rock types of intermediate-basic dykes are diabase, lamprophyre and diorite porphyry. LA-ICPMS zircon U-Pb dating results show that the age of the formation of Linglong area is 121.3 [3.8-123]. They have lower SiO2 (44.53-55.05 wt.) and higher MgO (6.77-13.26 wt%, Mg # = 64-73), higher K2O (1.5-4.4 wt.), higher Cr (383-818 ppm), Ni (135-328 ppm) and higher K20/Na2O ratio (0.60-1.82) in the silica-alkali map (TAS). The Sulu orogenic belt in the southern part of the peninsula is a part of the continental collision orogenic belt. The basic dykes are mainly diorite porphyrite. The LA-ICPMS zircon U-Pb dating results show that the ages of these dykes are 107.6 65507 They have high K20 (1.3-4.4 wt%) content, high Cr (108-1176 ppm), Ni (18.5-313 ppm) content and high K2O/Na2O (0.47-1.71) ratio. They fall mainly into syenite diorite and diorite on the silica-alkali map (TAS). On the maps of trace elements and rare earth elements, the intermediate-basic dikes in both areas are found. Rich in large ion lithophile elements (LILE) and light rare earth elements (LREE), depleted high field strength elements (HFSE) and heavy rare earth elements (HREE), showing obvious "arc" trace element distribution characteristics. Medium-basic dykes in Linglong area have higher initial 87Sr/86Sr (0.7092-0.7112) of the whole rock and lower initial values of epsilon Nd (t) (-12.3-19.6) and 206Pb/204Pb (17.6). Compared with Linglong area, Rushan area samples have slilower initial 87Sr/86Sr (0.7075-0.7094), low initial values of 87Sr/86Sr (0.7075-0.7094), low radiogenicvalues of epsilNd (t) (-10.9-15.7) and low initial values of 206Pb/204Pb (16.74-17.32), 207Pb/204Pb (16.74-17.32), 207Pb/204Pb (15.36-15.36-15.46), 208Pb (36-15.36-15.46), 208Pb (36-15.36-15.46), 208Pb (36-18.46), 20 8 Pb (36-8 Pb (36-18.89-89.89) and 208Pb (36/89.8 Pb (36 37.63). These geochemical characteristics indicate that the intermediate-basic dykes in the eastern Shandong area originate from the enriched mantle. The lower content of TiO2 and (Fe2O3) T indicates that their source areas are lithospheric mantle rather than asthenospheric mantle. The Sr-Nd-Pb isotope shows that they are closer to the lithospheric mantle of the North China Craton and farther from the lithospheric mantle of the Yangtze craton. The initial 87Sr/86Sr ratio and initial epsilon Nd(t) values do not change with Mg# values, indicating that the crustal contamination during the ascent is not significant, suggesting that the magma source of these "arc-shaped" trace element distribution characteristics of the intermediate-basic dikes in eastern Jiaodong is the metasomatic North China lithospheric mantle. The ratios indicate that the upper crustal material contributes to the mantle source area, and the two-stage Nd model ages of the whole rock are consistent with the UHP metamorphic rocks in the Sulu orogenic belt. The geochemical characteristics of the intermediate-basic dykes in the study area are similar to those of the Yinan gabbro near the Sulu orogenic belt, Fangcheng basalt and the basic volcanic rocks in the Jiaolai basin, but different from those of the Zouping area in Jinan, North China craton. It is believed that the subduction of the Yangtze Plate is the main reason for the difference between the two. The eastern part of Jiaodong and the eastern part of Shandong are subjected to greater subduction metasomatism near the Sulu orogenic belt and the inner part of the North China craton far from the orogenic belt is subduction metasomatism less. It is about 90 Ma later than the subduction/collision of the Yangtze Plate, suggesting that the orogenic event is obviously different from the melting of the lithospheric mantle in eastern Shandong. Mesozoic mantle-derived magma in Western Shandong is mainly concentrated in 185-177 Ma (asthenospheric origin) and 144-101 Ma (lithospheric origin), while mantle-derived magma in eastern Shandong is mainly concentrated in 185-177 Ma (asthenospheric origin) and 144- 34-102 Ma (lithospheric origin) and 95-73 Ma (asthenospheric origin), such age distribution characteristics are consistent with the subduction/retraction of the Paleo-Pacific Plate. Under the subduction and retraction of the Paleo-Pacific Plate, the eastern part of China changed from compressive background to extensional background, and the decompressive partial melting was the main mantle-derived magmatism in Shandong Province during the Early Cretaceous. Mechanism.
【學位授予單位】：中國科學技術(shù)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P588.124;P534.5
，
本文編號：2197585
[Abstract]:Since the Phanerozoic, many important geological events have taken place in eastern China, such as the destruction of the North China Craton, the convergence of the Yangtze plate and the North China Craton, and the subduction of the Paleo-Pacific Plate. The Jiaodong Peninsula is located in the eastern part of China's Central Orogenic Belt (Qinling-Dabie-Sulu orogenic belt), east of Bohai Bay, north of North China craton, south of Sulu orogenic belt. It is a study of deep lithospheric mantle composition and evolution. Natural Laboratory of Chemistry. In this paper, the early Cretaceous intermediate-basic dykes in Linglong and Rushan areas of the Jiaodong Peninsula are studied. Detailed petrography, zircon U-Pb age, major trace elements and Sr-Nd-Pb radiogenic isotope analysis of the whole rock are carried out. The data of Mesozoic mantle-derived intrusive rocks and volcanic rocks in Shandong Province are combined. Linglong area belongs to Jiaobei terrane, located in the northern part of Jiaodong Peninsula, and is a part of the North China Craton. The main rock types of intermediate-basic dykes are diabase, lamprophyre and diorite porphyry. LA-ICPMS zircon U-Pb dating results show that the age of the formation of Linglong area is 121.3 [3.8-123]. They have lower SiO2 (44.53-55.05 wt.) and higher MgO (6.77-13.26 wt%, Mg # = 64-73), higher K2O (1.5-4.4 wt.), higher Cr (383-818 ppm), Ni (135-328 ppm) and higher K20/Na2O ratio (0.60-1.82) in the silica-alkali map (TAS). The Sulu orogenic belt in the southern part of the peninsula is a part of the continental collision orogenic belt. The basic dykes are mainly diorite porphyrite. The LA-ICPMS zircon U-Pb dating results show that the ages of these dykes are 107.6 65507 They have high K20 (1.3-4.4 wt%) content, high Cr (108-1176 ppm), Ni (18.5-313 ppm) content and high K2O/Na2O (0.47-1.71) ratio. They fall mainly into syenite diorite and diorite on the silica-alkali map (TAS). On the maps of trace elements and rare earth elements, the intermediate-basic dikes in both areas are found. Rich in large ion lithophile elements (LILE) and light rare earth elements (LREE), depleted high field strength elements (HFSE) and heavy rare earth elements (HREE), showing obvious "arc" trace element distribution characteristics. Medium-basic dykes in Linglong area have higher initial 87Sr/86Sr (0.7092-0.7112) of the whole rock and lower initial values of epsilon Nd (t) (-12.3-19.6) and 206Pb/204Pb (17.6). Compared with Linglong area, Rushan area samples have slilower initial 87Sr/86Sr (0.7075-0.7094), low initial values of 87Sr/86Sr (0.7075-0.7094), low radiogenicvalues of epsilNd (t) (-10.9-15.7) and low initial values of 206Pb/204Pb (16.74-17.32), 207Pb/204Pb (16.74-17.32), 207Pb/204Pb (15.36-15.36-15.46), 208Pb (36-15.36-15.46), 208Pb (36-15.36-15.46), 208Pb (36-18.46), 20 8 Pb (36-8 Pb (36-18.89-89.89) and 208Pb (36/89.8 Pb (36 37.63). These geochemical characteristics indicate that the intermediate-basic dykes in the eastern Shandong area originate from the enriched mantle. The lower content of TiO2 and (Fe2O3) T indicates that their source areas are lithospheric mantle rather than asthenospheric mantle. The Sr-Nd-Pb isotope shows that they are closer to the lithospheric mantle of the North China Craton and farther from the lithospheric mantle of the Yangtze craton. The initial 87Sr/86Sr ratio and initial epsilon Nd(t) values do not change with Mg# values, indicating that the crustal contamination during the ascent is not significant, suggesting that the magma source of these "arc-shaped" trace element distribution characteristics of the intermediate-basic dikes in eastern Jiaodong is the metasomatic North China lithospheric mantle. The ratios indicate that the upper crustal material contributes to the mantle source area, and the two-stage Nd model ages of the whole rock are consistent with the UHP metamorphic rocks in the Sulu orogenic belt. The geochemical characteristics of the intermediate-basic dykes in the study area are similar to those of the Yinan gabbro near the Sulu orogenic belt, Fangcheng basalt and the basic volcanic rocks in the Jiaolai basin, but different from those of the Zouping area in Jinan, North China craton. It is believed that the subduction of the Yangtze Plate is the main reason for the difference between the two. The eastern part of Jiaodong and the eastern part of Shandong are subjected to greater subduction metasomatism near the Sulu orogenic belt and the inner part of the North China craton far from the orogenic belt is subduction metasomatism less. It is about 90 Ma later than the subduction/collision of the Yangtze Plate, suggesting that the orogenic event is obviously different from the melting of the lithospheric mantle in eastern Shandong. Mesozoic mantle-derived magma in Western Shandong is mainly concentrated in 185-177 Ma (asthenospheric origin) and 144-101 Ma (lithospheric origin), while mantle-derived magma in eastern Shandong is mainly concentrated in 185-177 Ma (asthenospheric origin) and 144- 34-102 Ma (lithospheric origin) and 95-73 Ma (asthenospheric origin), such age distribution characteristics are consistent with the subduction/retraction of the Paleo-Pacific Plate. Under the subduction and retraction of the Paleo-Pacific Plate, the eastern part of China changed from compressive background to extensional background, and the decompressive partial melting was the main mantle-derived magmatism in Shandong Province during the Early Cretaceous. Mechanism.
【學位授予單位】：中國科學技術(shù)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P588.124;P534.5
，
本文編號：2197585
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