CAJ | 학술논문

西秦岭造山带印支期岩浆活动十分频繁,发育在夏河—合作地区的德乌鲁石英闪长岩和老豆花岗闪长岩与区域上金矿床的形成密切相关。岩石地球化学特征表明，这两类岩石地球化学性质相似，均为过铝质钙碱性中性岩。微量元素具有富集大离子亲石元素LILE,如Rb、Th、U等和轻稀土元素，亏损Ba、K、Nb、Sr、Ti和低Sr和Y的特点。稀土元素组成表现为轻稀土富集而重稀土亏损，轻重稀土分馏强烈，且具有弱的负铕异常。LA-ICP-MS锆石U-Pb同位素测年获得2个德乌鲁石英闪长岩样品（LD103和LD107）的加权平均年龄分别为（245.8±1.7）Ma和（243.4±1.9）Ma(图10-a)，而3个老豆花岗闪长岩样品(LD102、LD106和LD113-2)的加权平均年龄分别为（241.4±2.1）Ma、（238.2±1.7）Ma和（241.4±1.6）Ma。德乌鲁石英闪长岩和老豆花岗闪长岩具有低Sr的特点,属于喜马拉雅型花岗岩，是由来自不同深源部分熔融形成的不同批次岩浆多次侵位聚集而成的，有利于与喜马拉雅型花岗岩有关的斑岩型Cu-Au、矽卡岩型Cu-Au和浅成低温Cu-Au-Sb矿床的形成。
서진령조산대인지기암장활동십분빈번,발육재하하—합작지구적덕오로석영섬장암화로두화강섬장암여구역상금광상적형성밀절상관。암석지구화학특정표명，저량류암석지구화학성질상사，균위과려질개감성중성암。미량원소구유부집대리자친석원소LILE,여Rb、Th、U등화경희토원소，우손Ba、K、Nb、Sr、Ti화저Sr화Y적특점。희토원소조성표현위경희토부집이중희토우손，경중희토분류강렬，차구유약적부유이상。LA-ICP-MS고석U-Pb동위소측년획득2개덕오로석영섬장암양품（LD103화LD107）적가권평균년령분별위（245.8±1.7）Ma화（243.4±1.9）Ma(도10-a)，이3개로두화강섬장암양품(LD102、LD106화LD113-2)적가권평균년령분별위（241.4±2.1）Ma、（238.2±1.7）Ma화（241.4±1.6）Ma。덕오로석영섬장암화로두화강섬장암구유저Sr적특점,속우희마랍아형화강암，시유래자불동심원부분용융형성적불동비차암장다차침위취집이성적，유리우여희마랍아형화강암유관적반암형Cu-Au、석잡암형Cu-Au화천성저온Cu-Au-Sb광상적형성。
The tectonic setting of western Qinling orogenic belt was studied through the research on the petrogeochemical characteristics and U-Pb age of zircon from Dawulu quartz-diorite and Laodou granitic-diorite using LA ICP-MS. These two <br> kinds of rocks belong to peraluminous calc-alkaline middle rocks. Trace element studies suggest that the rocks are predominately characterized by enrichment of LILE elements such as Rb, Th and U and other light rare-earth elements, depletion of Ba ,K, Nb, Sr, P, and low Sr and Y, suggesting typical characteristics of Himalaya-type granite. REE data indicate that the light rare earth elements were abundant, and heavy rare-earth elements are poor in these rocks. The light and heavy rare-earth fractionation is obvious.δEu has a weak negative anomaly. U-Pb age of zircon indicates that the weighted average ages of both Dewulu quartz-diorite and Laodou granitic diorite are (245.8 ± 1.7) Ma and (243.4 ± 1.9) Ma, (241.4 ± 2.1) Ma, (38.2 ± 1.7)Ma and (241.4 ± 1.6) Ma respectively, which suggests that these two intrusions formed at the earlier stage of Indosinian. It is pointed out that Laodou granitic diorite and Dewulu quartz diorite were derived from the different sources which came from the different depths, and the emplacement and accumulation were from multiple origins. The Laodou granitic diorite and Dewulu quartz diorite are projected into the range of arc magma. The tectonic setting research suggests that the western Qinling lies in the continental-to-continental collision in the earlier Indosinian period, and hence this region is favorable in search for porphyry Cu-Au deposits, skarn Cu-Au deposits and epithermal Cu-Au-Sb deposits.