Geological and Geochemical Characteristices of Songtan Hydrothermal Sedimentary Mangenes Deposits, Guizhuo
Chen Duofu Chen Xiangpei (Gangzhou Branch of Institute of Geochemistry Chinese Acsdemy of Scinces)
Songtao mangenes deposits, developed in the fine clastic sediments of Datangpo formation of Sinian, Guizhuo Province, belinging to carbonate deposits, have the following hydrothernal sedimentary geological and geochemical characteristices. 1. The mangenes deposits, yieldded in the high terrestrial heat extended margin basin area, poss "eye-like" structure both in lithofacies and in mangenes contents of single body of mangenes deposits. 2.The ore structures are mainly regularly distributed laminated-banded and meassive. It is usually massive in the center and then turned into banded-laminated to the edges. The thickness of bands and laminated are gradually finer and the number in creace to the sides. The bulk ores have the intraclast texture. 3. The ores are principally composited by Mn-carbonate, authigenic quartz and argillic minerals. Mn-carbonate and authigenic quartz are common in hydrothermal deposits. In addition, hydrothermal constitutions such as syngenetic barite, gypsum and pyrite ect. are found frequently. 4. The sample of the mangenes ores fell in the hydrothermal fiels of the diagrams of Fe- Mn-(Cu+Ni+Co× 10 and logU-logTh. The REE compositions in mangenes ores have the mixed features of hydrothermal and hydrogenic the estimated ratio of hydrothermal to hydrogenic compositon is about 70% to 30%. The REE distribution modet of the over lying argillites of the mangenes diposits is simlar to those of Nouth Amrica Shale, but it incline to the left in the underlying argillites, because of the effection of the hydrotherma solution. 5.δ~(13)C values of carbonates in the ores are -4.2-10.7%, close to that of soluted carbon in the hot spring water seafloor. δ~(34)S values of pyrits are +42.9-+57.3%, distribute as pagoda modle resulted from hydrothermal solution of sulphur from the crustal rocks. The initial ratio of ~(87)Sr / ~(86)Sr in the host rocks is 0.72391 ± 0.00132, similar to those of old salic rocks. The value of ores is 0.70595 ±0.00015, different from that of host rocks, between the 0.7909 of marine water and 0.7031 of seafloor hot spring water. 6. According to R°f pitchin the mangenes ores, the ores was formed under 170- 195℃ , similar to the inclusion temparature ( 173- 240℃ ) of the authibenic, quartz in the adjacent mangenes mine. Moreover, the temprature of the bottom of orebed is higher than that of the top, consistent with the hydrothermal characteristics.