南岔金矿床是吉林南部老岭金多金属成矿带内重要的中型金矿床，该矿区内矿体呈似层状、脉状和鞍状，主要赋存于老岭群珍珠门组与花山组接触带附近和蚀变闪长岩中。头道沟花岗岩侵入珍珠门组大理岩中，分布在矿区南东侧，呈小岩株状产出，岩性主要为似斑状黑云母花岗岩。锆石U-Pb定年结果表明，头道沟花岗岩锆石加权平均年龄为120 Ma±1 Ma，表明其结晶时代为早白垩世。全岩地球化学分析结果表明，头道沟花岗岩具有富硅，贫MgO、CaO等特点；相对富集K、Ba、Rb等大离子亲石元素和Th、U等活泼不相容元素，相对亏损Nb、Ta、P、Ti等高场强元素；稀土元素球粒陨石标准化配分曲线显示右倾型，具有微弱Eu负异常，反映源区有少量斜长石残留。该岩石属于高钾钙碱性系列向钾玄岩系列过渡的准铝质花岗岩，具有Ⅰ型花岗岩特征，推断岩石可能来源于加厚下地壳的部分熔融，是吉林省南部中生代晚期岩浆活动的代表，形成于造山后挤压向拉张过渡的后碰撞成岩构造环境，与古太平洋板块俯冲作用有关，与吉林省南部地区120 Ma左右的金矿化事件产于同一构造体制下。

Chance Gold Deposit is an important medium-scale gold deposit in the Laoling gold polymetallic metallogenic belt in southern Jilin Province.The ore bodies in the district are stratiform,in veins and saddle form,and      mainly occur near the contact zone between Zhenzhumen Formation and Huashan Formation of Laoling Group,as well as in the altered diorite.Toudaogou granite intrudes into the marble of Zhenzhumen Formation and is distributed in the southeast side of the district,occurring as a small stock and    mainly composed of porphyritic biotite granite.The zircon U-Pb dating shows the weighted mean zircon ages of Toudaogou granite are 120 Ma±1 Ma,indicating that the crystallization epoch is the early Cretaceous.The results of whole rock geochemical analysis show that Toudaogou granite are high in silicon content,and  low   in MgO and CaO content.The samples are relatively enriched in large ion lithophile elements such as K,Ba and Rb and active incompatible elements such as Th and U and are depleted in high field strength elements such as Nb,Ta,P and Ti.The REE distribution curve normalized to chondrite shows a right-declined type and weakly negative Eu anomaly,indicating the residue of a small amount of plagioclase in the source area.The rock belongs to a metaluminous granite transiting from high-K calc-alkaline to shoshonite series with I-type granite features,so it is inferred that Toudaogou granite probably originated from partial melting of thickened lower crust representing late Mesozoic magmatism in Southern Jilin Province,formed in the post collision diagenesis tectonic setting representing the transition from compression to extension after orogeny related to the subduction of the Paleo-Pacific plate,and occurred in the same tectonic setting with the gold mineralization event at about 120 Ma in southern Jilin Province.