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赣南寨背岩体主要为黑云母钾长花岗岩，黑云母结晶晚于长石和石英，锆石群型地温测量标尺显示其结晶温度为８００℃～９００℃，表明寨背岩体形成于一种高温贫水的花岗质岩浆。岩石的化学成分特点为准铝质（Ａｌ２Ｏ３为１２．２１％～１２．６２％），富硅（ＳｉＯ２为７５．６６％～７６．７４％），偏碱（Ｎａ２Ｏ＋Ｋ２Ｏ为７．９３％～８．９０％），ＦｅＯＴ／ＭｇＯ值高（５９～１４８），ＣａＯ和ＭｇＯ含量低（分别为０．１０％～０．６５％和０．０１％～０．０２％），富含ＲＥＥ（Ｅｕ除外，ΣＲＥＥ平均为５００μｇ／ｇ），Ｙ、Ｇａ、Ｎｂ等高场强元素（ＨＦＳＥ）以及Ｆ，Ｓｒ和Ｂａ较低。这些特点与本区的Ｉ型和Ｓ型花岗岩有明显差别，是一种典型的Ａ２型花岗岩。寨背岩体Ｒｂ－Ｓｒ等时线年龄为１７６Ｍａ，与辉长岩、双峰式火山岩有密切的时空关系，表明赣南地区在燕山早期即进入拉张裂解阶段。
The Gannan walled back porphyry mainly consists of biotite potassium long granite and biotite crystallites later than feldspar and quartz. The geothermometric scale of zircon assemblages shows that the crystallization temperature is 800 ℃ ~ 900 ℃, indicating that the molybdenite body is formed in one kind High-temperature water-poor granitic magma. The chemical composition of the rocks is characterized by quasi-aluminum (Al2O3 12.21% ~ 12.62%), silicon-rich (SiO2 75.66% ~ 76.74%), alkali (Na2O + K2O 7.93% ~ 8 .90%), high FeOT / MgO values (59-148), low CaO and MgO contents (0.10% -0.65% and 0.01% -0.02%, respectively) Except that ΣREE averaged 500μg / g), high field strength elements (HFSE) such as Y, Ga and Nb, and low F, Sr and Ba. These characteristics are obviously different from the type I and type S granites in this area, which is a typical type A2 granite. The Rb-Sr isochron age is 176 Ma, which is closely related to gabbro and bimodal volcanic rocks. It shows that Gannan region entered the early stage of extensional cracking in Yanshanian.