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Geochemical anomalies from a survey of stream sediments in the Maquelab area (Oecusse, Timor-Leste) and their bearing on the identification of mafic-ultramafic chromite rich complex
Applied Geochemistry ( IF 3.1 ) Pub Date : 2020-12-29 , DOI: 10.1016/j.apgeochem.2020.104868
Victor A.S. Vicente , João A.M.S. Pratas , Frederico C.M. Santos , Maria M.V.G. Silva , Paulo J.C. Favas , Luís E.N. Conde

Timor-Leste and Oecusse in particular have very little geological data coverage due to the many conflicts generated mainly by Portuguese colonization and Indonesian occupation. The main work that has been done was aimed at oil prospecting on the south coast. A regional stream sediment campaign was started from the Maquelab area in the Oecusse enclave, west of Timor-Leste, where no mineralization had been reported before. The geochemical characteristics of stream sediments in Maquelab area drainage basins, located in NW of Oecusse enclave, Timor-Leste, were investigated in order to establish the geochemical baseline conditions prior to any type of new mineral occurrences. Stream sediments demonstrated a different chemical composition with elevated values mainly for Cr (49–12,520 mg kg−1), Ni (11.6–863 mg kg−1) and Co (19.8–77.1 mg kg−1) which was not expected going by the present geological cartography of the area where the existence of ultramafic rocks is not supported. Principal component analysis (PCA) was used after centered log-ratio (CLR) transformation of data that allowed for the observance of different compositional groupings and the identification of the drainage basins they represented. Aided by the stream sediments geochemical results, a geological recognition of the area was then made, which allowed for the discovery of a new ultramafic complex, consisting of dunites, peridotites and serpentinites, containing metamorphic rocks, predominantly calc-silicate, basalts and gabbros. This complex is named the Maquelab Complex due to its proximity to this village. Inside the peridotitic rocks, small boulders of massive chromite with about 56% Cr2O3 were also found.



中文翻译:

Maquelab地区(Oecusse,东帝汶)河流沉积物调查的地球化学异常及其与富镁铁矿-超镁铁质铬铁矿复合物的鉴定有关

特别是东帝汶和欧库塞,由于主要是由葡萄牙殖民和印度尼西亚占领引起的许多冲突,所以地质数据的报道很少。已经完成的主要工作是针对南海岸的石油勘探。在东帝汶以西的欧库塞飞地的马奎拉布地区开始了区域性的河床泥沙运动,以前没有任何矿化的报道。为了确定在任何类型的新矿物出现之前的地球化学基线条件,对位于东帝汶欧库塞飞地西北部的马奎拉布地区流域的河流沉积物的地球化学特征进行了研究。河流沉积物显示出不同的化学成分,其主要用于铬(49–12,520 mg kg -1),镍(11.6–863 mg kg)的化学成分升高-1)和钴(19.8-77.1 mg千克-1),这是目前不支持超镁铁质岩石存在的地区的地质制图所无法预期的。在对数据进行中心对数比(CLR)转换后,使用主成分分析(PCA),以便观察不同的成分组并确定它们代表的流域。在河流沉积物地球化学结果的帮助下,对该区域进行了地质认识,从而发现了一种新的超镁铁质复合体,该复合体由辉长岩,橄榄岩和蛇纹岩组成,其中含有变质岩,主要是钙硅酸盐,玄武岩和辉长岩。该综合大楼因靠近该村庄而被称为Maquelab综合大楼。在橄榄岩内部,有块状铬铁矿的小巨石,其中含有约56%的Cr 2还发现了O 3

更新日期:2021-01-16
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