發(fā)布時(shí)間：2018-07-10 18:23

  本文選題：贊岐巖 + 基性巖墻��； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：在以往的研究中,華北地區(qū)的恒山、河北宣化、內(nèi)蒙古興和地區(qū)的“基性巖墻”所代表的為一種裂解伸展構(gòu)造背景,但近來,有研究提出這些“基性巖墻”可能為贊岐巖,代表了俯沖匯聚構(gòu)造背景。因此,廣泛出露于恒山—河北宣化—內(nèi)蒙古興和地區(qū)的大量古中元古代“基性巖墻”是否為贊岐巖,對于明確該地區(qū)在古元古代是匯聚還是伸展構(gòu)造背景,具有重要的科學(xué)意義。本文對恒山—河北宣化—內(nèi)蒙古興和古元古代的基性巖墻進(jìn)行了詳細(xì)的巖相學(xué)、礦物化學(xué)及地球化學(xué)研究。恒山—張家口宣化—內(nèi)蒙古興和地區(qū)的巖石手標(biāo)本可見典型的巖漿結(jié)構(gòu)—輝綠結(jié)構(gòu),其中恒山地區(qū)巖墻巖石主要是由具角閃石后成合晶的輝石、自形的斜長石和石榴石組成,其中斜長石主要為中長石、有成分環(huán)帶,輝石主要為火成鈣輝石及少量紫蘇輝石。河北宣化樣品巖石薄片光學(xué)顯微鏡下無明顯的輝綠結(jié)構(gòu),由石榴石、斜長石、單斜輝石、斜方輝石,角閃石組成。內(nèi)蒙古興和地區(qū)巖墻巖石主要由角閃石和中性斜長石組成,角閃石填充在斜長石組成的三角架中。恒山、宣化主量元素SiO2=50~51.3 wt.%、K2O=0.51~0.87wt.%、Na2O/K2O=2.8~4.7、MgO=5.8-6.7wt.%、Mg#=41.3~48.3,略富集相容元素(Ni=42.5~63.9μg/g,Cr=82~143μg/g,Co=48.7~58.6,V=349~395μg/g)和不相容元素(Sr=164~220μg/g,Ba=194~317μg/g,Rb=11.8~19.3μg/g),且輕稀土較重稀土富集(3.1LREE/HREE8.5),這與已發(fā)表的贊岐巖數(shù)據(jù)相似,但不相容元素和相容元素含量與贊岐巖相比都偏低,Mg#也不算很高;興和地區(qū)的Mg#(32.2~32.6)則更偏低,更富集不相容元素(Sr=373~375μg/g,Ba=1092~1097μg/g,Rb=50.1~52.6μg/g),相容元素則未見明顯富集(Ni=9.98~11.6μg/g,Cr=5.58~11μg/g),與贊岐巖的特征相差較大。此外,研究區(qū)的樣品普遍都存在富鐵和富鈦的特征。通過分析討論,可得出以下結(jié)論:(1)恒山、宣化、興和地區(qū)的基性巖墻不是典型的贊岐巖;(2)研究區(qū)這些巖墻為高鐵玄武質(zhì)巖石;(3)這些基性巖墻經(jīng)歷了一定程度的結(jié)晶分離作用和地殼混染作用。(4)這些基性巖墻很可能屬于板內(nèi)裂解的產(chǎn)物。
[Abstract]:In previous studies, the "basic rock walls" of Hengshan in North China, Xuanhua in Hebei and Xinghe in Inner Mongolia represent a kind of pyrolysis and extensional tectonic setting. But recently, some studies have suggested that these "basic rock walls" may be Zhanqi rocks. It represents the tectonic background of subduction convergence. Therefore, whether a large number of Paleoproterozoic "basic rock dikes" widely exposed in Hengshan-Xuanhua-Xinghe area, Inner Mongolia, are Zhanqi rocks, in order to determine whether the paleoproterozoic convergence or extension of the tectonic background in this area, It has important scientific significance. In this paper, the paleofacies, mineralogical chemistry and geochemistry of the basic rock wall of Heng Shan Xuanhua and Xinghe Gu Yuan in Inner Mongolia are studied in detail. Typical magmatic structure-pyrophyllite structure can be seen in the hand specimens of Hengshan Zhangjiakou Xuanhua area, Inner Mongolia. The rocks of the rock wall in Hengshan area are mainly composed of pyroxene with amphibole, plagioclase and garnet. The plagioclase is mainly meso-feldspar with compositional annulus and pyroxene is mainly pyrocalopyroxene and a small amount of perilla pyroxene. There is no obvious structure of phosphorescence in the thin slice optical microscope of Xuanhua sample in Hebei Province, which consists of garnet, plagioclase, clinopyroxene, clinopyroxene and hornblende. The rock wall rocks in Xinghe area, Inner Mongolia are mainly composed of amphibole and neutral plagioclase, and amphibole is filled in a tripod composed of plagioclase. 鎭掑北,瀹ｅ寲涓婚噺鍏冪礌SiO2=50~51.3 wt.%,K2O=0.51~0.87wt.%,Na2O/K2O=2.8~4.7,MgO=5.8-6.7wt.%,Mg#=41.3~48.3,鐣ュ瘜闆嗙浉瀹瑰厓绱，

本文編號：2114275