本文選題：華北克拉通東北緣 + 新太古代��； 參考：《吉林大學(xué)》2016年博士論文

【摘要】：鞍山-本溪地區(qū)位于華北克拉通東北緣,區(qū)內(nèi)保留了3.8Ga~2.5Ga的地質(zhì)記錄,是研究華北克拉通太古宙演化的理想?yún)^(qū)域。本文通過對鞍本地區(qū)太古宙變質(zhì)表殼巖的年代學(xué)、巖相學(xué)、巖石地球化學(xué)、構(gòu)造等進(jìn)行研究,再結(jié)合前人的一些研究成果,以探討鞍本地區(qū)綠巖帶的形成與演化。鞍本地區(qū)的變質(zhì)表殼巖主要由鞍山群組成,包括茨溝巖組、大峪溝巖組和櫻桃園巖組。來自于茨溝巖組斜長角閃巖的巖漿鋯石測年結(jié)果為2571±5.3Ma,與前人的測年結(jié)果基本一致,表明變質(zhì)表殼巖的成巖時(shí)代為新太古代晚期。鞍本地區(qū)變質(zhì)表殼巖的巖層層序相似:都是底部以變質(zhì)基性巖為主,局部含有少量變質(zhì)沉積巖;中部為條帶狀鐵建造,夾有少量變質(zhì)基性巖;頂部以變質(zhì)火山巖碎屑巖、沉積巖為主。只是不同區(qū)域的綠巖帶中變質(zhì)基性火山巖與變質(zhì)沉積巖所占比例不一樣。鞍本地區(qū)綠巖帶中的變質(zhì)基性巖具有平坦(TH1型)或輕微右傾(TH2型)的稀土配分模式曲線,在微量元素蛛網(wǎng)圖上,TH2型表現(xiàn)為較弱的Nb、Ti虧損,而TH1型則無Nb、Ti虧損。TH2型地球化學(xué)特征類似島弧拉斑玄武巖(IAT),TH1型與洋中脊玄武巖(MORB)相似。島弧拉斑玄武巖(IAT)和洋中脊玄武巖(MORB)的巖石組合、分布規(guī)律以及構(gòu)造環(huán)境判別圖解的投圖結(jié)果表明鞍本地區(qū)的變質(zhì)表殼巖形成于弧后盆地環(huán)境。離陸殼或火山弧較遠(yuǎn)的區(qū)域形成了以變質(zhì)中基性巖為主的巖石組合(茨溝巖組、大峪溝巖組),離陸殼或火山弧較近的區(qū)域形成以變質(zhì)沉積巖為主的巖石組合(櫻桃園巖組)。統(tǒng)計(jì)華北克拉通上各地區(qū)的花崗-綠巖帶的分布規(guī)律和巖石組合,然后根據(jù)以下幾點(diǎn)對這些花崗-綠巖帶進(jìn)行分帶:(1)是否存在老于2.55Ga的花崗質(zhì)巖石;(2)綠巖帶中變質(zhì)中基性巖屬于CAB、IAT還是MORB;(3)是否有高鎂安山巖存在;(4)2.55Ga之后的新太古代花崗巖類是TTG還是鉀質(zhì)花崗巖;(5)變質(zhì)沉積巖的碎屑物主要來源于火山弧還是由火山弧和陸殼共同提供。最終將華北克拉通東部的綠巖帶劃分為三個(gè)帶:西部的島弧帶(遼北-遼西-冀東-五臺一帶,可能延伸至登封一帶);中部微陸塊帶(以遷懷陸塊和膠遼陸塊為主);東部弧后盆地-陸緣帶(吉南-鞍本-膠東-魯西-舞陽-魯山一帶)。2.60Ga~2.53Ga,東部陸塊西側(cè)的洋殼向東俯沖,在東部陸塊的西部邊緣形成了島弧和弧后盆地,在島弧區(qū)形成了鈣堿性玄武巖(CAB)、島弧拉斑玄武巖(IAT)、安山巖(以高鎂安山巖為典型代表)、TTG的巖石組合,而在弧后盆地之中,則主要是洋中脊玄武巖(MORB)和島弧拉斑玄武巖(IAT)的組合,且離弧后盆地?cái)U(kuò)展中心越近,巖石地球化學(xué)特征越接近洋中脊玄武巖(MORB)�；『笈璧�-陸緣(本文中的大陸邊緣僅指陸塊邊緣,不包含弧后盆地、以及從大陸分離出去的陸緣弧)帶中存在大量老于2.55Ga的花崗巖類,可能是形成弧后盆地過程中從大陸邊緣拖拽出來的陸殼碎塊。弧后盆地在~2.53Ga開始閉合,弧后盆地中的洋殼開始向陸殼俯沖,同時(shí)大陸邊緣形成CAB、TTG和鉀質(zhì)花崗巖的巖性組合。2.52~2.47Ga為碰撞階段,殘留的洋殼受到擠壓變形,形成一系列NW-SE向的褶皺、韌性剪切帶和脆性斷裂,奠定了鞍本地區(qū)綠巖帶的基本構(gòu)造格局。洋殼變形的同時(shí)并受到低角閃巖相-綠片巖相區(qū)域變質(zhì)作用改造。第二次改造作用發(fā)生于~1.80Ga,主要受到遼吉裂谷閉合和后造山運(yùn)動(dòng)的影響,早期的斷裂重新活化。富Mg熱液沿這些斷裂運(yùn)移,對綠巖帶中的條帶狀磁鐵石英巖及其圍巖進(jìn)行改造,使磁鐵石英巖發(fā)生富集,并形成了一系列的蝕變巖。
[Abstract]:The Anshan Benxi area is located on the northeastern margin of the North China Craton. The geological record of the 3.8Ga~2.5Ga is retained in the area. It is an ideal area for the study of the Archean evolution of the North China Craton. This paper has studied the chronology, petrography, petrochemistry and construction of the Archean metamorphic crust rocks in the sellar area, and then combined with some previous research results. The formation and evolution of the greenstone belt in the sellan area are discussed. The metamorphic surface rocks in the sellan area are mainly composed of Anshan groups, including the zigigite group, the dagugou rock group and the Cherry Orchard Group. The result of the magmatic zircon dating from the diagonal amphibolite from the yuziguiganyan group is 2571 + 5.3Ma, which is basically consistent with the previous survey results, indicating the formation of metamorphic case rocks. The rock age is late Neoarchean. The strata sequence of metamorphic topical rocks in the Sanben area is similar: the base is mainly metamorphic base rock with a small amount of metamorphic sedimentary rocks, the middle part is constructed with strip iron, with a small amount of metamorphic base rock, and the top is metamorphic volcanic clastic rock and sedimentary rock. The proportion of the sexual volcanic rocks is different from that of metamorphic sedimentary rocks. The metamorphic base rocks in the greenstone belt in the sellar area have a flat (TH1) or a slight right (TH2) rare-earth distribution pattern curve. On the trace element cobweb map, the TH2 type shows weak Nb, Ti loss, and TH1 type no Nb, Ti loss.TH2 type geochemical characteristics resembling island arc spots. Xuan Wuyan (IAT), TH1 type is similar to the mid ocean ridge Xuan Wuyan (MORB). The rock assemblage of the island arc pullout Xuan Wuyan (IAT) and the mid ocean ridge Xuan Wuyan (MORB), the distribution pattern and the mapping results of the tectonic setting diagram show that the metamorphic crust in the saddle area is formed in the back arc basin environment. The far areas from the continental crust or volcanic arc formed to metamorphism. The rock assemblage of the middle base rock (ditgou rock group, daku Gou rock group), the rock assemblage of metamorphic sedimentary rocks (Cherry Orchard Group) in the area near the continental crust or volcanic arc. The distribution law of granite greenstone belt in the North China Craton and the rock assemblage of the granite greenstone belt in the North China Craton are counted, and then the granite greenstone is brought into the following several points. Line Zoning: (1) whether there are granitic rocks old in 2.55Ga; (2) the metamorphic base rocks in the greenstone belt belong to CAB, IAT or MORB; (3) there are high magnesium andesite; (4) the Neoarchean granitoids after 2.55Ga are TTG or potassic granites; (5) the detritus of the metamorphic sedimentary rocks is mainly derived from the volcanic arc or the volcanic arc and the continental crust. In the end, the greenstone belt in the eastern North China Craton is divided into three zones: the western island arc belt (Liaodong - Liaoxi - Jidong - five area, possibly extending to Dengfeng), and the central micro - continental block (mainly migrating continental block and gelatin land block), and the eastern arc basin - the marginal zone (Zilin - Jiaodong Luxi Wuyang - Lushan Mountain Lushan Mountain) .53Ga, the oceanic crust on the west side of the eastern continent subducts eastward, forming island arcs and back arc basins on the western edge of the eastern continental block. In the island arc, the calc basalt (CAB), island arc tholeiite (IAT), andesite (typical of high magnesium andesite) and TTG rock assemblage, and in the back arc basin, are mainly the middle ocean ridge basalt ( MORB) and the combination of island arc pulping basalt (IAT), and the closer to the extension center of the post arc basin, the more close to the oceanic ridge basalt (MORB). The back arc basin - the continental margin (the continental margin in this article only refers to the continental margin, does not contain the back arc basin, and the continental margin arc separated from the continent) is a large number of old 2.55Ga The granitoids may be the continental crust fragments which were dragged from the continental margin in the process of the back arc basin. The back arc basin began to close in ~2.53Ga, and the oceanic crust in the back arc basin began to subduction to the continental crust, and the continental margin formed CAB, and the lithologic combination of TTG and potassic granite was.2.52~ 2.47Ga as the collision stage, and the residual oceanic crust was squeezed and deformed. The formation of a series of NW-SE folds, ductile shear zones and brittle fracture, laid the basic structural pattern of the greenstone belt in the sellar area. The deformation of the oceanic crust was simultaneously transformed by the metamorphism of the low amphibolite phase and the greenschist facies region. The second transformation occurred at ~1.80Ga, mainly influenced by the closure of the Liaoji Rift Valley and the post orogenic movement. The fracture of the period is reactivated. The rich Mg hydrothermal fluid is migrated along these faults, and the strip magnetite quartzite and its surrounding rock in the greenstone belt are reformed to enrich the magnetite quartzite and form a series of altered rocks.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P588.3
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本文編號：2076131