| The tectonic province of Luanchuan ore-concentrated area is situated in theconjunction of southern margin of the North China Craton and North Qinlingorogenic belt, in which strata, structures, metamorphic zones and magmatitedistributed in the NWW-NW trending. Structures of different directions, charactersand periods have widely developed under the multiple complex deformation since lateProterozoic Era. Intricate structural morphology were caused by the multiply changesof mechanics in faults’ plane. In the area, the NWW-NW and the NNE-NE trendingare the most developed structure features and they together formed a network fabrics,whose intersections are often the favorable metallogenic spaces.Based on the previous studies and acquired achievements, this paper focused onthe characteristics of deep structures by means of field investigations and first-handdata collection, indoor analyses, as well as emphasis on Line-N00profile which isacross the core region of Luanchuan ore-concentrated area, combined withCSAMT(Controlled Source Audio-frequency Magneto Tellurics) and geophysical datasuch as artificial earthquake and gravity. The following conclusions and discussionswere put forward to explain structural characteristics and rock-controlling andore-controlling factors of Luanchuan ore-concentrated area.1.Structural characteristics are mainly reflected in following aspects:Theore-concentrated area experienced multi-episodic deformation. A large thrust nappestructural system formed under the continent-continent collision of the Yangtze Blockand North China Block since the Indosinian, triggering the obduction of North ChinaPlate from north to south and causing a typical thin-skinned structure whose nappeinterface is the contact surfaces between strata and magmatite. The faults performedas imbricate thrust nappe system, manifesting high angle thrust characteristics. Foldsin the thrust nappe system performed recumbent types and showed top-to-the-southand tight isoclinal reverse morphological characteristics, with the evident compositecharacteristic of the E-W and N-S trending superposition. The thrust nappe structure extended as a piggyback model from south to north.2. Characteristics of rock-controlling and ore-controlling structures in Luanchuanore-concentrated area are shown as follows: the structural framework is chieflyformed by the NWW-NW trending and the NNE-NE trending network fabrics, havinga great impact on the distribution and shapes of the deposits and ore bodies.3. The deposits have close relationship with Yanshanian medium-acid plutons inspatial, temporal and genesis. small porphyritic plutons distribute in the near E-Wtrending belts as well as direction of the NNE by the composite controlling of theNWW-NW trending and the NNE-NE trending.4. Before Yanshanian period, the NWW-NW fabrics gradually formed under N-Scompressive stress field; In Yanshanian period, the mechanism of stress field transitedfrom compression to extension NWW-NW trending structures were transformed byNNE-NE trending structure. The intersections between the two groups of faultsprovided the intruding space for magma activity, which was favorable for theemplacement of I-type granites emplacing. Acidic magma intruded through the spaceand access, which triggered. Metallogenic belt macroscopically performs in the EWtrending while the main ore-controlling fault is in the NNE trending. |
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