本文選題：早白堊世 + 膠東半島　； 參考：《中國地質大學(北京)》2017年博士論文

【摘要】：在膠東半島,廣泛發(fā)育早白堊世基性脈巖群并與金礦床密切伴生。本文選取膠東早白堊世基性脈巖進行系統(tǒng)研究,探究脈巖成因演化和形成動力學機制,不僅為膠東半島深部構造演化提供重要信息,而且可初步探討基性脈巖與大規(guī)模金成礦的關系。膠東基性脈巖受區(qū)域構造控制展布,巖石類型以煌斑巖和輝綠巖為主。最新年代學研究厘定基性脈巖主要形成于早白堊世(130~110 Ma),基性脈巖均具有島弧型基性巖漿特征,如低SiO2、高MgO、Cr和Ni含量、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)、高(87Sr/88Sr)i比值、低?Nd(t)和?Hf(t)值,指示其來源于華北克拉通(NCC)富集巖石圈地幔。高Dy/Yb比值反映脈巖巖漿源自含角閃石二輝橄欖巖在尖晶石-石榴石相過渡區(qū)低程度部分熔融。巖漿演化過程中,脈巖巖漿經歷了橄欖石和單斜輝石的分離結晶,地殼混染作用不明顯�；悦}巖具有低δ26Mg值,表明其地幔源區(qū)經歷了碳酸鹽交代�；悦}巖具有低Os含量和高187Os/188Os值指示地幔源區(qū)經歷了以流體為主的俯沖交代作用從而形成大量的富集巖脈,該富集巖脈與橄欖巖圍巖發(fā)生部分熔融,熔體混合形成基性脈巖巖漿。此外,蘇魯基性脈巖與膠北基性脈巖同位素特征存在輕微差異,指示三疊紀時期揚子克拉通(YC)向NCC俯沖交代作用的影響。中生代時期,古太平洋板塊向西俯沖交代改造了上覆NCC巖石圈地幔。早白堊世時期,板片回撤以及伊邪那岐板塊改變俯沖方向,導致NCC東部巖石圈地幔伸展-減薄,并伴隨軟流圈的上涌。巖石圈地幔底部被軟流圈上升所帶來的熱持續(xù)侵蝕而發(fā)生部分熔融,形成島弧型基性脈巖巖漿。上涌的軟流圈地幔降壓熔融產生洋島型基性脈巖巖漿。通過典型礦區(qū)基性脈巖與金礦對比研究發(fā)現(xiàn),膠東基性脈巖從成礦前、成礦期到成礦后均有產出,但是脈巖形成的高峰期在成礦期;基性脈巖與金礦脈緊密伴生產出,成礦流體與基性巖漿均具有幔源特征;但基性脈巖鉑族元素特征揭示,脈巖巖漿源自地幔的低程度部分熔融,導致大量的親硫元素(PGEs和Au)留在了地幔,基性脈巖可能沒有為膠東大規(guī)模金成礦提供幔源成礦物質。
[Abstract]:In Jiaodong Peninsula, the early Cretaceous basic dike rock group is widely developed and is closely associated with the gold deposit. In this paper, the early Cretaceous basic dikes in Jiaodong were studied systematically, and the genetic evolution and dynamic mechanism of the dikes were explored, which not only provided important information for the evolution of the deep structure of the Jiaodong Peninsula. Furthermore, the relationship between basic dikes and large-scale gold mineralization can be preliminarily discussed. The basic dikes of Jiaodong are controlled by regional tectonics, and the main rock types are lamprophyre and diabase. According to the latest geochronological study, the basic dikes were mainly formed in the early Cretaceous, and the basic dikes were characterized by island arc basic magma, such as low Sio _ 2, high MgO _ (2) Cr and Ni contents. The enrichment of large ion lithophile elements LILE) and light rare earth elements (LREEN), the depletion of high field strength elements (HFSEI), the high ratio of 87 Sr / 88 Sr ~ (2 +), and the values of low ~ (87) ND ~ (8) S ~ (+) and HfT) indicate that they are derived from the enriched lithospheric mantle of the North China Craton (NCCs). The high Dy/Yb ratio indicates that the dike magma originated from amphibole-bearing pyroxenite in low degree partial melting in the spinel-garnet phase transition zone. In the process of magmatic evolution, the dike rock magma experienced the separation and crystallization of olivine and clinopyroxene, and the crustal mixing was not obvious. The low 未 26Mg value of the basic dike rocks indicates that the mantle source region experienced carbonate metasomatism. The low Os content and high 187Os/188Os value of the basic dikes indicate that the mantle source region experienced fluid dominated subduction and metasomatism, resulting in the formation of a large number of enriched veins, which partially melted with the surrounding rock of peridotite. The melt mixes to form the basic dike magma. In addition, there is a slight difference in isotopic characteristics between the basic dikes of Sulu and Jiaobei, indicating the influence of the Yangtze craton (YC) subduction and metasomatism to NCC during the Triassic. During the Mesozoic, the paleo-Pacific plate subducted westward and transformed the NCC lithospheric mantle. In the early Cretaceous period the plate retreat and the change of the subduction direction of the Ixonaki plate resulted in the extension and thinning of the lithospheric mantle in the eastern part of NCC and the upwelling of the asthenosphere. The lithospheric mantle bottom is partially melted by the continuous thermal erosion caused by the rise of the asthenosphere and the island arc type basic dike magma is formed. The upwelling asthenosphere mantle depressurizes and melts to produce the oceanic island type basic dike magma. Through the comparative study of basic dikes and gold deposits in typical ore areas, it is found that the basic dikes of Jiaodong are produced from pre-metallogenic, metallogenic to post-metallogenic, but the peak of dike formation is in metallogenic period, and the basic dikes and gold veins are produced closely together. Both the ore-forming fluid and the basic magma have mantle-derived characteristics, but the elemental characteristics of the platinum group of the basic dike rocks reveal that the dike magma originated from the low degree of partial melting of the mantle, resulting in a large number of sulphophilic elements such as PGEs and Au) remaining in the mantle. Basic dikes may not provide mantle-derived minerals for large-scale gold mineralization in Jiaodong.
【學位授予單位】：中國地質大學(北京)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P588.12;P618.51
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本文編號：1945608