新疆地质
新疆地質
신강지질
XINJIANG GEOLOGY
2013年
3期
248-255
,共8页
尹利君%刘继顺%杨立功%刘卫明
尹利君%劉繼順%楊立功%劉衛明
윤리군%류계순%양립공%류위명
都兰%A型花岗岩%LA-ICP-MS锆石U-Pb年龄%地球化学%白石崖花岗岩
都蘭%A型花崗巖%LA-ICP-MS鋯石U-Pb年齡%地毬化學%白石崖花崗巖
도란%A형화강암%LA-ICP-MS고석U-Pb년령%지구화학%백석애화강암
Dulan region%A-type granite%LA-ICP-MS zircon U-Pb age%Geochemistry%Baishiya granite
白石崖铁矿为都兰地区一处典型的矽卡岩型铁多金属矿床。通过对花岗岩年代学和岩石地球化学研究表明，白石崖花岗岩侵位于（238±1） Ma，富硅（SiO2=70.01%~76.01%）、富碱（K2O+Na2O=6.64%~8.41%）、FeO*/MgO比值（平均22.87）较高、贫镁（MgO=0.04%~0.39%），K2O/Na2O>1，A.I.=0.88~0.99，A/CNK=0.62~0.83，属偏铝钙碱性岩石；稀土分布曲线呈“海鸥式”分布特征，显示较强的Eu负异常（δEu=0.10~0.70）；微量元素特征显示具较高的Zr （172×10-6~205×10-6）、Nb（11×10-6~31×10-6）和Y（21.9×10-6~50.1×10-6），较低的Sr（40×10-6~223×10-6）、Ba（168×10-6~690×10-6）；在微量元素原始地幔标准化蛛网图上显示明显的Ba，Sr，P和Ti的负异常，表明白石崖花岗岩为A型花岗岩。结合区域构造演化，认为该区花岗岩形成于造山后的伸展环境，属A2型花岗岩。三叠纪时，东昆仑地区处于后碰撞构造阶段，俯冲板片发生断裂，岩石圈拆沉，引发大范围的地壳伸展减薄，软流圈物质上涌，上涌的软流圈物质与地壳直接接触，对上覆长英质地壳的直接加热作用促使其部分熔融，长石、榍石等分离结晶，形成该区A型花岗岩。
白石崖鐵礦為都蘭地區一處典型的矽卡巖型鐵多金屬礦床。通過對花崗巖年代學和巖石地毬化學研究錶明，白石崖花崗巖侵位于（238±1） Ma，富硅（SiO2=70.01%~76.01%）、富堿（K2O+Na2O=6.64%~8.41%）、FeO*/MgO比值（平均22.87）較高、貧鎂（MgO=0.04%~0.39%），K2O/Na2O>1，A.I.=0.88~0.99，A/CNK=0.62~0.83，屬偏鋁鈣堿性巖石；稀土分佈麯線呈“海鷗式”分佈特徵，顯示較彊的Eu負異常（δEu=0.10~0.70）；微量元素特徵顯示具較高的Zr （172×10-6~205×10-6）、Nb（11×10-6~31×10-6）和Y（21.9×10-6~50.1×10-6），較低的Sr（40×10-6~223×10-6）、Ba（168×10-6~690×10-6）；在微量元素原始地幔標準化蛛網圖上顯示明顯的Ba，Sr，P和Ti的負異常，錶明白石崖花崗巖為A型花崗巖。結閤區域構造縯化，認為該區花崗巖形成于造山後的伸展環境，屬A2型花崗巖。三疊紀時，東昆崙地區處于後踫撞構造階段，俯遲闆片髮生斷裂，巖石圈拆沉，引髮大範圍的地殼伸展減薄，軟流圈物質上湧，上湧的軟流圈物質與地殼直接接觸，對上覆長英質地殼的直接加熱作用促使其部分鎔融，長石、榍石等分離結晶，形成該區A型花崗巖。
백석애철광위도란지구일처전형적석잡암형철다금속광상。통과대화강암년대학화암석지구화학연구표명，백석애화강암침위우（238±1） Ma，부규（SiO2=70.01%~76.01%）、부감（K2O+Na2O=6.64%~8.41%）、FeO*/MgO비치（평균22.87）교고、빈미（MgO=0.04%~0.39%），K2O/Na2O>1，A.I.=0.88~0.99，A/CNK=0.62~0.83，속편려개감성암석；희토분포곡선정“해구식”분포특정，현시교강적Eu부이상（δEu=0.10~0.70）；미량원소특정현시구교고적Zr （172×10-6~205×10-6）、Nb（11×10-6~31×10-6）화Y（21.9×10-6~50.1×10-6），교저적Sr（40×10-6~223×10-6）、Ba（168×10-6~690×10-6）；재미량원소원시지만표준화주망도상현시명현적Ba，Sr，P화Ti적부이상，표명백석애화강암위A형화강암。결합구역구조연화，인위해구화강암형성우조산후적신전배경，속A2형화강암。삼첩기시，동곤륜지구처우후팽당구조계단，부충판편발생단렬，암석권탁침，인발대범위적지각신전감박，연류권물질상용，상용적연류권물질여지각직접접촉，대상복장영질지각적직접가열작용촉사기부분용융，장석、설석등분리결정，형성해구A형화강암。
The Baishiya mine is a typical skarn iron polymetallic deposit in Dulan region. The LA-ICP-MS analyses of zircons from the granite yield a weighted mean 206Pb/238U age of (238±1)Ma. The granites are characterized by high SiO2 (70.01%~76.01%), high alkali(K2O+Na2O=6.64%~8.41%), but low MgO contents(0.04%~0.39%), and high FeO*/MgO ratios(22.87, on average). The granites are of subaluminous and calc-alkaline with K2O/Na2O>1,A.I.=0.88~0.99, A/CNK=0.62~0.83. The Baishiya granites are marked by a“sea-gull”pattern of REE distribution withδEu ranging from 0.10 to 0.70, showing a relatively strong negative Eu anomaly. These rocks are enriched in Zr(172×10-6~205×10-6), Nb (11×10-6~31×10-6)and Y(21.9×10-6~50.1×10-6), but depleted in Sr(40×10-6~223×10-6)and Ba contents(168×10-6~690 × 10-6), and exhibit significantly negative Ba, Sr, P and Ti anomalies on the primitive mantle-normalized trace ele-ment diagram. All these characteristics resemble A-type granites which originated from the partial melting of felsic crust under high temperature and low pressure condition and the subsequent fractional crystallization of feldspar, titanite, etc. Coupled with regional tectonic evolution, we suggest that the Baishiya granites belong to A2 type granites and be formed in post-orogenic tectonic setting. During the Triassic, the East Kunlun was under a transitional tectonic regime from com-pression to extension, where the break off of subducted slab and the delamination of lithosphere led to extensive thinning of the crust and the upwelling of the asthenosphere. The upwelling asthenosphere provided enhanced heat flux and trig-gered the partial melting of the overlying felsic crust and then produced the Baishiya granites.
