山东地区中生代岩浆作用与地壳拉张-兼论煌斑岩与金成矿的关系

GYIG OpenIR > 研究生 > 学位论文

	山东地区中生代岩浆作用与地壳拉张-兼论煌斑岩与金成矿的关系
其他题名	The Mesozoic magmatism and crustal extension in Shandong Province, China-additionally discussing the relationship between lamprophyres and gold mineralization
	刘燊
	2004
学位授予单位	中国科学院地球化学研究所
学位授予地点	中国科学院地球化学研究所
学位名称	博士
学位专业	地球化学
关键词	中生代富集地幔地壳拉张地壳混染岩石成因煌斑岩金矿山东省
摘要	燕山期（205～65Ma）山东地区地壳活动强烈，构造体系已由古亚洲构造域完全转化为滨太平洋构造域，构造活动导源于太平洋板块对欧亚板块的俯冲。由于太平洋板块对欧亚板块的俯冲（NW向），鲁东地区岩石圈发生了快速拆沉减薄作用．同时鲁东地区也可能会出现地l漫柱的活动；另外，在太平洋板块俯冲作用影响下，炎区庐断裂（山东称沂沐断裂）带发生了大型左行走滑剪切和拉张活动。以上构造因素加上早白至世末一晚白至世期间燕山造山带的垮塌，都可能为山东地区中生代地壳拉张提供了动力条件。山东地区中生代（燕山期）基性脉岩特别发育，这些慢源基性岩脉充填张性裂隙，是大陆地壳拉张的标志；另外，山东地区也存在大量拉张背景下的燕山期火山岩和碱性岩。但关于它们的年代学和系统的地球化学研究还比较薄弱，且对其成因和形成的构造环境，仍存在着争议。本论文主要从同位素年代学、岩石化学、地球化学和Sr-Nd-Pb同位素方面对山东地区燕山期基性脉岩、火山岩和碱性超基性脉岩进行了系统研究。同时，考虑到鲁东地区煌斑岩中金含量普遍较高，且燕山期又是山东金矿的主成矿期，论文中对煌斑岩与金成矿之间的关系也作了一定的研究。通过研究，得出以下主要认识：1、火山岩为一套以钙碱性安山岩为主，含少量拉斑玄武岩和英安岩。成因上为富集地慢部分熔融作用的结果，但在成岩过程中也可能存在单斜辉石、斜长石、橄榄石和Ti-Fe氧化物等矿物的分离结晶作用。碱性超基性脉岩岩性上为单一的橄榄辉石岩，为富集地慢源低度（3.4％）部分熔融作用的产物，岩浆演化过程经历了以橄榄石为主的分馏作用。基性脉岩主要包括辉长岩、辉绿岩（主要分布在鲁西地区）和煌斑岩（以斜闪煌斑岩为主，同时含部分拉辉煌斑岩和角闪煌斑岩）（主要分布在鲁东地区），都为富集岩石圈地慢部分熔融的产物。三类岩石在侵位结晶过程都不存在明显的地壳混染。2、火山岩、碱性超基性脉岩和基性脉岩（除少数外）都形成于大陆板内拉张环境。3、富集地慢源区（EMI）的产生是俯冲并熔融的扬子下地壳物质进入华北岩石圈地慢并与之相互交代作用形成的。4、研究区中生代基性脉岩K-Ar年龄分布范围为72.2±1.70Ma～204.2±5.4Ma，且基本上在90～140Ma之间变化。综合碱性超基性脉岩和已知的青山组的火山岩、基性脉岩年龄数据，认为山东地区中生代地壳拉张至少存在四次：即约80Ma、100Ma、120Ma和 140Ma。但鲁东地区在地壳拉张方面可能存在着与鲁西地区不同的制约因素：即鲁东地区存在拆沉作用和可能存在地慢柱的影响，而鲁西地区可能受到了郊庐断裂的左行走滑剪切和拉张活动的影响。5、胶北地区煌斑岩为钙碱性系列，且金含量普遍较高（平均28ppb），该研究对胶北地区的找矿勘探工作具有一定意义。
其他摘要	The crustal movement was intense in Yanshanian, from 205Ma to 65Ma in Shandong Province, When the tectonic system completely changed from paleo-Asian tectonic circle to shore Pacific tectonic circle, and established the'elementary tectonic framework of Shandong Province. From then on, the tectonic movements of Shandong were ascribed to the subduction (north-west-trending) of Pacific plate under Eurasian. Due to the west north direction s.ubduction, fast collapse (delamination) may take place and the mantle plume emerged; in Ludong, In addition, owing to the subduction of Pacific plate under Eurasian, there appeared left-lateral advection and extension for Tan-Lu faults (named as Yishu fault in Shandong), and together with the collapse of Yanshanian orogenic belts, all induced the crustal extension in Shandong The Yanshanian mafic dikes, volcanic rocks and alkaline rocks resulting from extensional setting largely appeared in Shandong Province. However, - it' is unsubstantial for the investigation on chorology and geochemisty, and dissimilar for the research on petrogenesis and tectonic setting. Therefore, based on the isotopic chorology, petrochemistry, geochemisty and Sr, Nd, Pb isotope, the Ph.D dissertation mainly studied some Yanshanian mafic dikes, volcanic rocks and alkalic-ultramafic dikes in. Shandong Province. In addition, in view of the high gold contents in: the iamprpphyres, and the significance of Yanshanian for gold mineralization: in Shandong, the relation between lamprophyres and gold deposit is alsodiscussed in this paper. By studying., the main conclusions have,been achieved as follows: 1.The volcaojc rocks, as the result of the partial melting of enriched mantle, comprise, calc-ajkaline andesite and dacite and a few tholeiite. During diagenetic process, there may exist the fractional crystallization of clino-pynoxene, plagioclase; olivine and Ti-Fe oxide, and the accumulation of olivine. The alkalic-ultramafic dikes formed by low degree partial melting. (3.4%) of enriched mantl&y consist of single olivine pyroxenolite, the dominating olivine fractionation is evident. The mafic dikes also formed by the partial melting of enriched mantle, include gabbro, diabase (distributing mainly in Luxi) and lamprophyres (camptovogesite, odinite and hornblende lamprophyres) (mainly in Ludong). For all the rocks, crustal contamination was absent when magma empiaced. 2. The mafic dikes, volcanic rocks and alkalic-ultramafic dikes are terrestrial, and were all formed in the extensional settings. 3. The formation of the enriched mantle (EM1) is attributed to the strong metasomatism-taking place between subducted Yangtze lower crust and NC (north of China) ancient lithosphere. Due to the subduction of Pacific palte under Eurasian in early Cretaceous, at about 140 Ma, fast collapse (delamination) took place and the mantle plume emerged, both resulted in the large-scale crustal extension in Ludong. In addition, owing to the subduction of Pacific plate under Eurasian, there appeared left-lateral advection and extension for Tan-Lu faults (named as Yishu fault in Shandong), and which induced the crustal extension in Luxi. Under the cooperation of lifts and mantle fluids, the melting point of mantle peridotite fell, and then, extensive melting took place in the enriched mantle, which resulted in the appearance of abundant mafic dikes, ultramafic dikes and contemporaneous volcanic rocks in Shandong Province. Moreover, in view of the speeds of collapse, extension and magmatic emplacement were so fast that no crustal contamination in magma. 4.The K-Ar isotopic data of mafic dikes vary between 72.2±1.70Ma and 204.2±5.4Ma, and mostly between 90 Ma and 140 Ma. Integrating the ages of the mafic dikes and alkalic-ultramafic dikes in this paper, and the known data of mafic dikes and volcanic rocks, at least, there existed four episodes Mesozoic crustal extension in Shandong Province, namely, 80Ma, 100Ma, 120 Ma and140Ma, which is similar to that of SC (South China), indicating that maybe the effect of the subduction of ancient Pacific plate (Izanaqi or Kula) under Eurasian on EC (east of China). Mesozoic crustal extension mainly was controlled by the different factors in Ludong and Luxi. In Ludong, the crustal extension may be attributed to the activities of delamination and mantle plume, While in Luxi, the crustal extension was owed to the left-lateral advection and extension of Tan-Lu faults. 5.The gold contents of the calc-alkaline lamprophyres in Jiaobei are high (average in 28 ppb), which is significative for the exploration in the future.
页数	95
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3694
专题	研究生_研究生_学位论文矿床地球化学国家重点实验室
推荐引用方式 GB/T 7714	刘燊. 山东地区中生代岩浆作用与地壳拉张-兼论煌斑岩与金成矿的关系[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,2004.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
LW013719.pdf（2633KB）			暂不开放	--	请求全文