Effect of sulfate evaporate salt layer for formation of porphyrite iron ores in the Middle-Lower Yangtze River area

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	Effect of sulfate evaporate salt layer for formation of porphyrite iron ores in the Middle-Lower Yangtze River area
	Li YanHe 3; Duan Chao ; Han Dan ; Chen XinWang 1; Wang CongLin 1; Yang BingYang 1; Zhang Cheng ; Liu Feng
刊名	ACTA PETROLOGICA SINICA
	2014
卷号	30 期号:5 页码:1355-1368
关键词	Porphyrite iron ores Sulfate evaporate salt layers Oxidation barrier Iron ore magma delta S-34 The Middle-Lower Yangtze area
ISSN号	1000-0569
英文摘要	The Middle-Lower Yangtze Polymetallic Ore Belt is one of the most important metallogenic belts in East China, comprising more than 200 polymetallic (Cu-Fe-Au, Mo, Zn, Pb, Ag) deposits. Ningwu and Luzong ore distrcts are the most important component of this belt. In these districts, volcanic-subvolcanic rocks, intrusions and subvolcanic rocks-related iron deposits which are well known as porphyrite iron deposits in China are widespread, during the Late Mesozoic. Based on the geological characteristics, spatial distribution and relationship with volcanic-subvolcanic rocks, the famous iron porphyrite deposit model has been established which improved the development of metallogenic theory and the effective guidance of porphyrite deposit prospecting greatly. This mineralization model emphasizes mainly magmatic-hydrothermal role, but the sulfate evaporate salt layers, at the top of the Zhouchongcun group in Middle Triassic, did not cause the attention in the role of mineralization. And this model mainly reflects the mineralization in shallow. The latest researches and prospecting results reveal that the Middle Triassic sulfate evaporates salt layers and mineralization has closely relationship. However, the ore-controlling mechanism of evaporate salt layers has still been unrevealed, "sulfate evaporate salt layers as oxidation barrier" in porphyry ore mineralization role rarely reported. In this paper, sulfur isotope characteristics of porphyrite iron deposits have been studied in Middle-Lower Yangtze River Polymetallic Ore Belt, and evaporate salt layers oxidation barrier in porphyry ore mineralization role has been revealed. Porphyrite iron deposits and Fe-S deposits commonly contain gypsum, and iron deposits, Fe-S deposits and gypsum deposits are paragenesis closely. In these deposits, the values of sulfide delta S-34(V-CDT) are abnormally high, and the average values are higher than 5 parts per thousand. Most of the values of gypsum delta S-34(V-CDT) are about 20 parts per thousand, which are similar to the value of marine sulfate. Sulfur isotopic composition of the deposits is closely related with the genesis types, with the reduced sulfur isotope value from ore magma type to ore magma-hydrothermal type to hydrothermal type. Such as the values of sulfide delta S-34(V-CDT) are 10.8 parts per thousand from Gushan deposit, 7.85 parts per thousand from Meishan deposit and 5.01 parts per thousand from Washan deposit. The variation of sulfur isotopic composition of the deposits is mainly controlled by the sulfate reduced temperature and the proportion of original magma sulfur. The higher sulfate reduced temperature is, the higher sulfide delta S-34 value is. And the higher proportion percent of the original magma sulfur is the lower sulfide delta S-34 value. The calculate results obtained that most of sulfur is derived from sulfates in evaporate salt layers, and the proportion is approximately 60%similar to 80%. The reduction temperature is more than 450 degrees C. The temperature of the sulfide precipitation was lower and relatively later. Thus, we infer that evaporate salt layers not just provide a large number of agents of mineralization for the sodium alteration, scapolitization and skarn alteration, like Na+, Cl-, CO32- and so on, but also course the Fe2+ transport as the complex (e.g. Na-Fe-Cl). On the other hand, the evaporate salt layer is the most important oxidation barrier in the depth crust, which could oxidize the Fe2+ into Fe3+ in the silicate magma and hydrothermal solution, and enrich the iron to be the iron deposit. It is a critical factor of the ore-forming of the porphyrite iron deposit. While the magma is assimilating evaporate salt layers (CaSO4), SO42- oxidize Fe2+ into Fe3+ in the silicate melt, which prevent Fe2+ to enter the lattice silicate minerals, with forming Fe3O4/Fe2O3 and poor iron silicate minerals like diopside, actinolite, tremolite and so on. The immiscibility occurs between iron oxide and silicate melt in magma chamber, by the effects of P, NaCl and volatile, forming the iron ore magma. The iron ore magma has strong viscous behavior, with short migration distance, penetrating along favorable structural parts, near the contact zone of intrution and salt layers. It forms ore magma type or like-skarn type iron deposit like Gushan and Meishan deposits. Metallogenic hydrothermal has strong mobility, transporting in the form of iron complex, with long migration distance, concentrating and precipitating in the distal the contact zone of intrution and salt layers, like the volcanic rocks covering the subvolcanic rocks. These two type iron deposits coexist in the porphyrite iron deposit family with a certain spatial zonation, forming the "double-metallogenic structure". In the contact zone of intrution and salt layers, there might present the Daye ore magma-skarn iron deposit, with high grade and high reserve, and the scale may exceed the iron deposit occurred in the shallow part of subvolcanic rocks or volcanic rocks. And, SO42- itself is reduced into S2-, while it is oxidizing the Fe2+, and S2- combine with Fe2+ to form pyrite, in the top or side portion of the iron deposit. These are underlying reasons of paragenesis closely among iron deposits, Fe-S deposits and gypsum deposits.
学科主题	矿床地质
WOS关键词	U-PB GEOCHRONOLOGY ; LU-ZONG BASIN ; VOLCANIC-ROCKS ; NINGWU BASIN ; ANHUI PROVINCE ; EASTERN CHINA ; KIRUNA-TYPE ; MAGNETITE ; DEPOSIT ; VALLEY
WOS研究方向	Geology
语种	中文
出版者	SCIENCE PRESS
WOS记录号	WOS:000337205700012
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/40411]
专题	中国地质科学院矿产资源研究所
作者单位	1.Chinese Acad Geol Sci, Inst Mineral Resources, MLR Key Lab Metallogeny & Mineral Assessment, Beijing 100037, Peoples R China 2.Maanshan Iron & Steel Grp Min Co, Nanshan Mine, Maanshan 243033, Peoples R China 3.中国地质科学院矿产资源研究所
推荐引用方式 GB/T 7714	Li YanHe,Duan Chao,Han Dan,et al. Effect of sulfate evaporate salt layer for formation of porphyrite iron ores in the Middle-Lower Yangtze River area[J]. ACTA PETROLOGICA SINICA,2014,30(5):1355-1368.
APA	Li YanHe.,Duan Chao.,Han Dan.,Chen XinWang.,Wang CongLin.,...&Liu Feng.(2014).Effect of sulfate evaporate salt layer for formation of porphyrite iron ores in the Middle-Lower Yangtze River area.ACTA PETROLOGICA SINICA,30(5),1355-1368.
MLA	Li YanHe,et al."Effect of sulfate evaporate salt layer for formation of porphyrite iron ores in the Middle-Lower Yangtze River area".ACTA PETROLOGICA SINICA 30.5(2014):1355-1368.