矿床地球化学国家重点实验室知识库

China has a rich reserve of iron ores and hosts most of the major types of iron deposits recognized worldwide. However, among these, the banded iron formation (BIF), skarn, apatite–magnetite, volcanic-hosted, sedimentary hematite and magmatic Ti–Fe–(V) deposits constitute the most economically important types. High-grade iron ores (> 50% Fe) are relatively rare, and are mostly represented by the skarn-type. Most of the BIF deposits formed in the Neoarchean, with a peak at ~ 2.5 Ga, and are mainly distributed in the North China Craton. The majority of these is associated with volcanic rocks, and therefore belongs to the Algoma-type. The superior-type BIF deposits formed during the Paleoproterozoic occur subordinately (ca. 25%), and are related mainly to rifts (or passive continental margins). In addition, minor Superior-type BIF deposits have also been recognized. The skarn iron deposits are widely distributed in China, especially in the uplifted areas of eastern China, and form several large iron ore clusters. These ore deposits are genetically associated with intermediate, intermediate-felsic and felsic intrusions with a peak age of formation at ca. 130 Ma. They display common characteristics including alteration and nature of mineralization. The apatite–magnetite deposits occurring in the Ningwu and Luzong Cretaceous terrigenous volcanic basins along the Middle–Lower Yangtze River Valley, are spatially and temporally associated with dioritic subvolcanic intrusions. The ores in this type are characterized by magnetite and apatite. The volcanic-hosted iron deposits are associated with submarine volcanic-sedimentary sequences, and are widely distributed in the orogenic belts of western China, including Western Tianshan, Eastern Tianshan, Beishan, Altay, Kaladawan area in the eastern part of the Altyn Tagh Mountain and southwestern margin of South China Block. These deposits show a considerable age range, from Proterozoic to Mesozoic, but with more than 70% were formed in the Paleozoic, especially during the Late Paleozoic. The metallogenesis in these deposits can be correlated to the space–time evolution of the submarine volcanism, and their relationship to volcanic lithofacies variation, such as central, proximal and distal environments of ore formation. The sedimentary hematite deposits are widespread in China, among which the “Xuanlong-type” in the North China Craton and the “Ningxiang-type” in the South China Block are the most economically important. All these deposits formed during transgressions in a shallow-marine environment. Magmatic Ti–Fe–(V) deposits are dominantly distributed in the Panxi area in Sichuan province and Chengde area in Hebei province. They are dominated low-grade disseminated ores, and unlike the other types of iron deposits, associated sulfide deposits are absent, with magnetite, titanomagnetite and ilmenite as the dominant ore minerals. In the Panxi area in the central Emeishan large igneous province along the western margin of South China Block, the ores are hosted in the ca. 260 Ma mafic layered intrusions, whereas the ores in the Chengde area are associated with the Mesoproterozoic anorthosite complex. The distinct spatio-temporal characteristics of the various iron deposits in China correlate with the multiple tectono-magmatic events associated with the prolonged geological history of the region involving accretion, assembly and rifting.