CAJ | 학술논문

微古化石资料和前人研究表明，相山铀矿田基底变质岩原岩时代为新元古代青白口纪。文章通过野外地质调查和系统采样对这套变质岩的原岩组成和形成环境进行了分析。大部分变质碎屑岩样品以中等SiO2含量、高的K2O/Na2O值和较高的Fe2O3T+MgO及低的CaO含量为特征。所有样品的稀土元素具有∑REE总量较大、轻稀土富集和Eu亏损的特征。稀土元素分布模式图解中各样品的总体组成模式相当接近，稀土配分型式为右倾式，与后太古宙页岩和上地壳相似。西蒙南图解和涅洛夫图解表明，神山组原岩主要为复矿物砂岩和长石砂岩，库里组原岩主要为石英岩质砂岩及长石砂岩；上施组原岩主要为长石砂岩及少量硅质泥灰岩、泥质砂岩。结合变余构造特征分析认为，这套变质碎屑岩形成于滨浅海—陆棚沉积环境。所有样品中Th/Sc比值变化范围较小(0.5~1.1)，而Zr/Sc比值变化范围较大(8~24)，揭示了变质岩源区成分复杂，可能经过多次沉积循环。在Th-Sc-Zr/10和La-Th-Sc图解中，大部分数据落入大陆岛弧区，说明该套岩石可能沉积于靠近大陆岛弧的相关盆地。Hf-La/Th图解表明，原岩的物源大部分来源于古老地层的抬升剥蚀，酸性岛弧源区仅占少数，说明其沉积时期岩浆活动并不明显，而物源区伴有构造隆升，结合地化特征分析推测赣中相山基底变质岩原岩形成于华夏地块与扬子板块后碰撞伸展环境下的残留海盆。
미고화석자료화전인연구표명，상산유광전기저변질암원암시대위신원고대청백구기。문장통과야외지질조사화계통채양대저투변질암적원암조성화형성배경진행료분석。대부분변질쇄설암양품이중등SiO2함량、고적K2O/Na2O치화교고적Fe2O3T+MgO급저적CaO함량위특정。소유양품적희토원소구유∑REE총량교대、경희토부집화Eu우손적특정。희토원소분포모식도해중각양품적총체조성모식상당접근，희토배분형식위우경식，여후태고주혈암화상지각상사。서몽남도해화열락부도해표명，신산조원암주요위복광물사암화장석사암，고리조원암주요위석영암질사암급장석사암；상시조원암주요위장석사암급소량규질니회암、니질사암。결합변여구조특정분석인위，저투변질쇄설암형성우빈천해—륙붕침적배경。소유양품중Th/Sc비치변화범위교소(0.5~1.1)，이Zr/Sc비치변화범위교대(8~24)，게시료변질암원구성분복잡，가능경과다차침적순배。재Th-Sc-Zr/10화La-Th-Sc도해중，대부분수거락입대륙도호구，설명해투암석가능침적우고근대륙도호적상관분지。Hf-La/Th도해표명，원암적물원대부분래원우고로지층적태승박식，산성도호원구부점소수，설명기침적시기암장활동병불명현，이물원구반유구조륭승，결합지화특정분석추측공중상산기저변질암원암형성우화하지괴여양자판괴후팽당신전배경하적잔류해분。
Located in the suture zone of the Cathaysia and Yangtze tectonic belt and lies on the southern side of Jiangshao fault, the Xiangshan uranium orefield is the largest volcanic uranium orefield and is also the earliest discovered volcanic uranium orefield in China. Its basement is a set of ancient metamorphic rock series. Micro palaeophyte fossils and previous studies indicate that the basement metamorphic rocks formed in the Qingbaikou period of Neoproterozoic. This paper mainly discusses the composition of metamorphic rock and analyzes its formation environment. Most metamorphic samples are characterized by intermediate SiO2 content, high K2O/Na2O and Fe2O3T+MgO, and obviously low CaO content. Analytical results of all samples show larger totalΣREE values and abundant LREE, as well as depletion of Eu, implying that the rock samples originated from the continental crust. The overall compositions of various sample patterns are very close to each other in the REE distribution diagram, and REE patterns of all samples are of right-oblique type, similar to patterns of the post-Archean shale and the upper crust. From the Simonen and Nielv diagram, the authors infer that the original rocks of Shenshan Formation were mainly composed of complex mineral sandstones and feldspathic sandstone, the original rocks of Kuli Formation consisted mainly of quartzite sandstone and feldspathic sandstone, and the original rocks of Shangshi Formation comprised mainly feldspathic sandstone, with a little siliceous marl and shale sandstone. Combined with residual structural features analysis, it is inferred that these metamorphic clastic sedimentary rocks formed in a shallow shore-shelf sedimentary environment. Th/Sc ratios of all samples vary in a small range (0.5-1.1) , while Zr/Sc ratios vary quite considerably (8-24), revealing the complex composition of the source region of the metamorphic rocks and the probable existence of several sedimentary cycles. In Th-Sc-Zr/10 and La-Th-Sc diagram, most of the data fall into the continental island arc area, indicating that this set of rocks might have been deposited in the basins near the continental island arc. Hf-La/Th diagrams indicate that the provenance of the original rock mostly came from ancient strata of uplift and erosion, and acidic arc source region only possessed a small proportion. It is thus obvious that the magmatic activity during its deposition was not obvious, but the source region was accompanied by tectonic uplift. Combined with geochemical characteristics, it is held that the protoliths of basement metamorphic rocks in the Xiangshan uranium orefield were formed in the residual basin of an extension environment, resulting from the post-collision between Cathaysia and Yangzi Blocks.