诸广山南体“三九”地区花岗岩的成因研究和铀成矿潜力探讨

发布时间：2018-06-07 22:25

本文选题：诸广山南体 + 铁质花岗岩　；参考：《南京大学》2015年硕士论文

【摘要】：诸广山南体是南岭铀矿成矿带的重要组成,该地区铀矿主要产于中部和东部,均为花岗岩型铀矿床,西部至今尚未发现铀矿化。前人对诸广山南体东部和西部的花岗岩开展了一些研究工作,而中北部的“三九”地区关注较少,研究程度相对薄弱。本文选择“三九”地区桃金洞、东岭、九龙和中棚四个花岗岩体作为研究对象,进行了成岩年代厘定,并综合运用岩相学、元素地球化学和Sr-Nd同位素等研究手段,对四个花岗岩的岩石成因与构造背景进行了探讨,同时,在与诸广山南体其他产铀和非产铀花岗岩对比的基础上,初步评估了它们的产铀潜力。LA-ICP-MS锆石U-Pb定年结果显示,桃金洞花岗岩的年龄为204±2.1 Ma,为印支晚期岩浆活动的产物。岩石地球化学组成上,桃金洞花岗岩为过铝质(除一个样品的ASI=0.98,其余为1.02-1.12),铁相对于镁略富集的特征,属于碱钙性或钙碱性-铁质花岗岩；稀土元素总量较高(∑REE=225.6～271.9×10-6),富集LREE(LREE/HREE=6.27～11.4,(La/Yb)N=4.01～15.0),Eu亏损较明显(6Eu=0.15～0.42)；富集Rb.Th和U,亏损Ba、Sr、Ti和Eu,属于典型的低Ba、Sr花岗岩。同位素组成上,桃金洞花岗岩(87Sr/86Sr)i值较高(0.71922～0.72040)εNd(t)值较低(-10.0～-10.2),两阶段Nd模式年龄为1.80～1.82 Ga。岩石地球化学特征表明,桃金洞花岗岩属于典型的壳源型花岗岩,是在地壳伸展—减薄背景下,古元古代变质杂砂岩经过中低程度部分熔融形。东岭、九龙和中棚三个花岗岩的成岩年龄分别为161.9±1.5 Ma、162.9±2.3Ma和148.2±1.9 Ma,为燕山早期岩浆作用的产物。它们均表现为富铁、贫镁和过铝质(ASI=1.00～1.12)的特征,属于碱钙性或钙碱性—铁质花岗岩。东岭、九龙和中棚三个花岗岩均具有较高的Si02(平均75.9%),高的Rb/Sr比值(平均22.2)以及明显的Eu负异常(0.04～0.23),表明岩浆经历了强烈的结晶分异作用。对比东岭、九龙花岗岩和长江花岗岩(图2-4中的长江岩体)的地球化学特征,认为它们具有相似的岩石成因类型,它们的εNd(t)值较低(-9.6--10.8),两阶段Nd模式年龄较古老(1.73 Ga～1.83 Ga),两者源区为砂质岩和泥质岩的混合。它们是在伸展构造背景下,由古元古代变质沉积岩部分熔融形成。中棚花岗岩的地球化学和同位素特征与粤北产铀的帽峰花岗岩和南岭产钨花岗岩相似,具有较低的εNd(t)值(-9.6--10.4)和较古老的Nd模式年龄(1.70 Ga～1.80Ga)为古元古代变质泥岩在伸展构造背景下部分熔融形成。对比研究显示,相对于诸广山南体非产铀花岗岩,该区典型的产铀花岗岩蚀变作用较强；FeOT/(FeOT+MgO)比值变化较大,多为铁质花岗岩,反映相对还原的特征；并且CaO含量更低,Ba、Sr、Ti和Eu亏损更强烈；非产铀花岗岩中的铀主要赋存在锆石、钍石等副矿物中,岩石后期热液蚀变作用不明显。因此,与非产铀花岗岩特征相似的桃金洞花岗岩铀成矿潜力有限,与产铀花岗岩相似的东岭、九龙和中棚花岗岩具有一定的铀成矿潜力,其中,中棚花岗岩具有稀土元素四分组效应,可能具有较大的铀成矿潜力。
[Abstract]:The Zhuguang Shannan body is an important component of the Nanling uranium metallogenic belt. The uranium deposit in this area is mainly produced in the middle and East, all of which are granite type uranium deposits. The uranium mineralization has not been found in the west to the present. The predecessors have carried out some research work on the granite in the eastern and western parts of the southern Shannan body, while the "39" area in the north and the North has paid less attention and the degree of research is less. It is relatively weak. This paper selects four granite bodies in "39" area, peach gold cave, Dongling, Kowloon and middle shed as research objects, and carried out diagenetic dating, and comprehensively applied petrography, elemental geochemistry and Sr-Nd isotopes to study the petrogenesis and tectonic setting of the four granites. On the basis of the comparison of other uranium producing and non uranium producing granites in Sannan body, the preliminary evaluation of their uranium potential.LA-ICP-MS zircon U-Pb dating shows that the age of the peach golden cave granite is 204 + 2.1 Ma, which is a product of late Indosinian magmatic activity. 8, the rest is 1.02-1.12, which is characterized by the slightly enriched iron, which belongs to the alkali calcium or calc alkaline iron granites; the total amount of rare earth elements is higher (REE=225.6 ~ 271.9 * 10-6), enriching LREE (LREE/HREE=6.27 to 11.4, (La/Yb) N=4.01 15), Eu loss is obvious (6Eu=0.15 to 0.42), Rb.Th and U, Ba in the loss, Sr, Sr, U, etc. Low Ba, Sr granite. On the isotope composition, the I value of peach golden cave granite (87Sr/86Sr) is higher (0.71922 ~ 0.72040), Nd (T) is lower (-10.0 to -10.2), and the two stage Nd mode age is 1.80 ~ 1.82 Ga. rock geochemical characteristics, and the peach golden cave granite is a typical crust source granite, which is in the background of crust extension and thinning, Gu Yuangu The generation of metamorphic complex sandstone is partially melted in middle and low degree. The age of three granites in Dongling, Kowloon and middle shed are 161.9 + 1.5 Ma, 162.9 + 2.3Ma and 148.2 + 1.9 Ma, which are the products of early magmatism in Yanshan. They are all characterized by iron rich, poor magnesium and peraluminous (ASI=1.00 to 1.12), belonging to alkali calcium or calc alkaline iron. Three granites in Dongling, Kowloon and middle shed have high Si02 (average 75.9%), high Rb/Sr ratio (average 22.2) and obvious negative Eu anomaly (0.04 ~ 0.23), indicating that the magma experienced a strong crystallization differentiation. They have similar petrogenesis types, their Nd (T) values are lower (-9.6--10.8), the two stage Nd model age is older (1.73 Ga to 1.83 Ga), and the source region is a mixture of Sandy and argillaceous rocks. They are formed by the melting of Paleoproterozoic metamorphic rocks under the extensional tectonic setting. The characteristics of the position are similar to the Gufeng granite and Nanling wolfram granites in North Guangdong, with lower epsilon Nd (T) value (-9.6--10.4) and older Nd mode age (1.70 Ga to 1.80Ga) as Paleoproterozoic metamorphic mudstones formed partially by the extensional tectonic setting. The typical uranium granites have strong alteration, FeOT/ (FeOT+MgO) ratio varies greatly, most of which are iron granites, reflecting the characteristics of relative reduction; and CaO content is lower, Ba, Sr, Ti and Eu are more strongly depleted; the uranium in the non uranium granites mainly exists in the secondary minerals such as zircon and thorium, and the late hydrothermal alteration of the rocks is not obvious. The mineralization potential of the Tao Jin Dong granite, which is similar to the non uranium bearing granite, is limited. The Dongling, similar to the uranium bearing granite, has a certain uranium metallogenic potential in the Dongling, the Kowloon and the middle shed granites, of which the medium shelf granite has the four grouping effect of rare earth elements, which may have large uranium metallogenic potential.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.14;P588.121

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