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石碌铁矿床位于海南岛五指山褶皱带西段.矿区内外发育以闪长玢岩脉为主的中基性脉岩.LA-ICP-MS锆石U-Pb定年厘定闪长玢岩脉年龄为248±1Ma(MSWD=0.4),为早三叠世岩浆活动的产物,与同时代的富碱侵入岩体构成“双峰式”侵入岩.闪长玢岩脉为钾玄质系列,低SiO2(49.18%～55.25%)、高Al2O3(14.36%～16.75%)、FeOt(5.98%～10.07%)和MgO(3.80%～5.43%),富集LILE和LREE,亏损HFSE.Nb/Ta、Zr/Hf和La/Nb比值分别为15.33～17.80、36.00～45.23和2.59～8.62;Pb同位素组成(206Pb/204Pb)t=18.087～18.483,(207Pb/204Pb)t=15.473～15.587,(208Pb/204Pb)t=38.272～38.817.LREE/HFSE和LILE/HFSE比值及Pb同位素组成显示为富集地幔来源,但混染有少量的地壳物质.HFSE判别图解指示闪长玢岩脉形成于大陆边缘弧伸展背景,与晚二叠世印支板块NE向向华南地块俯冲造成的大陆边缘弧局部伸展有关.
The Shilu iron deposit is located in the western section of the Wuzhishan fold belt in the Hainan Island, with the development of middle-basic plutons dominated by diorite porphyrite in and out of the mines. The zircon U-Pb dating of LA-ICP-MS was used to determine the diorite porphyrite age Is 248 ± 1Ma (MSWD = 0.4), which is a product of the Early Triassic magmatism and constitutes a “bimodal” intrusive rock with the same alkali-rich intrusive rocks.The diorite veins are of the K + (49.18% ~ 55.25%), high Al2O3 (14.36% ~ 16.75%), FeOt (5.98% ~ 10.07%) and MgO (3.80% ~ 5.43%), enrich LILE and LREE, Ta, Zr / Hf and La / Nb ratios were 15.33 ~ 17.80, 36.00 ~ 45.23 and 2.59 ~ 8.62, Pb isotopic compositions were 206.0bp-204.4b, 207pb / 204Pb was 15.473-15.587, 208Pb / 204Pb) t = 38.272 ~ 38.817. The ratios of LREE / HFSE to LILE / HFSE and Pb isotopic compositions are shown to be enriched in mantle sources but mixed with a small amount of crustal material. The HFSE discriminant diagram indicates that the diorite veins formed on the continent The extension of the marginal arc is related to the local extension of the continental marginal arc caused by NE subduction of the Late Permian Indosinian Plate in South China.