汤中立院士提出的“小岩体成大矿”理论，是基于对与镁铁-超镁铁质侵入岩有关的岩浆铜镍硫化物矿床长期调查研究得出的概括性成矿认识总结。一经提出即得到了国内外勘查界的普遍响应，大量的矿床勘查实践，有力地证明了浅成的较小体积的侵入岩却往往形成了较大规模金属储量的矿床。本文主要通过对西北地区与镁铁-超镁铁岩有关的岩浆铜镍硫化物矿床成矿作用的研究，对“小岩体成大矿”的成因进行深入探讨，认为幔源岩浆深部熔离-贯入作用，是形成小岩体成大矿的主要机理。国外提出的“岩浆通道”说，可以导致成矿的局部富集，与小岩体成大矿的机理认识是一致的。通过对西北地区大量岩浆铜镍硫化物矿床找矿事实的总结，进一步丰富了“小岩体成大矿”科学内涵，对指导找矿有重要的现实意义。

The theory on small intrusions forming large deposits put forward by academician Zhongli Tang was a recapitulative summary by Long-term studying of magmatic Ni-Cu sulfide deposits which related to mafic-ultramafic intrusions. And this theory got a common response by exploration industry in the world. Many mineral exploration practices have effectively illustrated that the hypabyssal and small intrusion could always form the larger ore deposits. Our study is about the mineralization of Ni-Cu sulfide deposits which related to mafic-ultramafic intrusions in the northwestern of China. In this paper，we have discussed the theory of small intrusions forming large deposits，considering that mantle magma deep part liquation and injection is the main mechanism of this theory. And another theory of magma conduit systems，may cause the local enrichment of mineral，and like that theory of small intrusions forming large deposits. After summarizes the prospecting fact of magmatic Ni-Cu sulfide deposits in the northwestern of China，we expand the scientific connotation of the theory on small intrusions forming large deposits，and make it more realistic meaningful in guiding prospecting.