Монография посвящена изучению вторичных биогеохимических и литохимических ореолов рассеяния в ландшафтных условиях золотоносных районов Верхнего Приамурья. Рассмотрена информативность различных видов высших растений при биогеохимическом методе поисков и гранулометрических классов фракций рыхлых отложений при минералого-геохимическом методе поисков. Показана результативность применения биогеохимического метода как для поисков золотосеребряного оруденения, так и для эколого-геохимической оценки загрязнения окружающей среды, в пределах Приамурской золотоносной провинции. Книга представляет интерес для геологов, геохимиков, занимающихся поисками золоторудных и других месторождений, а также для преподавателей и студентов геологических и географических специальностей вузов.

Предлагаемая книга из серии «Полезные ископаемые Республики Башкортостан» является первой частью издания, посвященного золотому оруденению Республики. В ней характеризуются золото-рудные объекты, принадлежащие к золото-кварцевой, золото-сульфидной и золото-колчеданно-полиметаллической (баймакский тип) формациям. Здесь же приводятся сведения по колчеданным место-рождениям уральского типа в связи с их золотоносностью.

На страницах монографии, кроме собственных материалов, обобщены все имеющиеся на сегодняшний день данные, разбросанные в многочисленных публикациях и производственных отчетах, с целью воссоздания реальной картины распространенности золота на территории Республики и перспектив его добычи.

В книге, с различной степенью детальности, кратко описано свы-ше 150 золоторудных месторождений, рудопроявлений и точек ми-нерализации. Характеристика объектов дана согласно их формационной принадлежности и особенностям ведущих минеральных ассоциаций.

Кроме этого, раскрыты общие закономерности размещения золотого оруденения. На основе анализа литературных материалов, под-робно рассмотрено поведение золота при различных физико-химических параметрах во флюидных системах.

Книга рассчитана на широкий круг читателей и, в первую очередь, на специалистов в области геологии и металлогении, а также студентов геологического профиля. Она будет полезна предпринимателям, занимающимся вопросами добычи полезных ископаемых.

Оценка перспектив глубоких горизонтов и флангов месторождений рудного золота представляет собой сложную геологическую задачу, решение которой возможно комплексом геофизических методов, включающим электроразведку на постоянном и переменном токе. Повышение геологической информативности электроразведки в осложненных условиях рудных узлов и полей Прибайкалья (альпинотипный рельеф, малая мощность и субвертикальные углы падения рудных тел, криолитозона, курумы, высокие переходные сопротивления) во многом связано с совершенствованием современной аппаратурно-технической базы, развитием методик 2D, 3D-моделирования и инверсии, учета основных искажающих факторов.

We used samples from six Finnish ore deposits to evaluate the efficiency of sample pretreatment procedures — crushing, splitting and grinding — and to compare three analytical methods based on the atomic absorption determination of gold following: (1) classical lead fire assay (FA); (2) the aqua regia leach (AR) followed by Hg coprecipitation of Au; and (3) the sodium cyanide (NaCN) leach. Sample size used for the method comparison is 20 g. The Au deposits and ore types were: Suurikuusikko and Osikonma¨ki, refractory ores in which Au is associated with arsenopyrite and pyrite; Pampalo and Kutemaja¨rvi ores with metallic Au and Au tellurides; and Jokisivu and Pahtavaara ores containing coarse-grained metallic Au. After crushing, the samples were split into three parts, one of which was put aside into storage. Two splits were further divided into two subsamples which were ground to two grades of fineness (<0.03 and <0.06 mm). The four subsamples thus obtained were analysed for Au using the three analytical methods. Each determination was performed five times on each of the four subsamples. According to t-tests on the FA results of the two splits, crushing and splitting produced samples of equal Au content in all six cases. Grinding to a finer grain size gave a significant difference in Au results only for the Pahtavaara ore sample. If the FA results are assumed to represent 100% recovery of Au, we obtained greater than 95% recoveries for all but the Suurikuusikko sample (87% recovery) by the AR leach method. We also obtained recoveries of over 95% by the NaCN leach method for the Pampalo, Kutemaja¨rvi and Pahtavaara samples, whereas recoveries for the other three samples varied between 73 to 92%. The AR leach was also performed on 1-g samples and the NaCN leach on 250-g samples. For three of the ore samples, decreasing sample size from 20 g to 1 g did not cause a significant difference in the variance of the Au results. Increasing the sample size from 20 g to 250 g significantly improves the representativity of only the Pahtavaara sample. For the Kutemaja¨rvi, Pahtavaara and Jokisivu ores, a sample larger than 250 g is needed in order to obtain a precision equivalent to that for reference samples.

Conventionally, geochemical exploration for gold is based on the assumptions that (1) gold is chemically inert in surficial environments; (2) gold occurs mainly in discrete grains; and (3) gold is transferred by mechanical means to form clastic dispersion halos and dispersion trains. Consequently, the commonly adopted methodology has been (1) to determine gold in heavy mineral concentrates; (2) to use large samples in order to improve the reproducibility of gold analyses; (3) to use high detection limits and thresholds; and (4) to determine total gold contents and pathfinder elements in the samples. However, these methods are not always successful in locating gold deposits, and they have limited application in the search for buried or blind deposits.

In China, studies of the distribution and migration of particulate and ultrafine gold indicated that (1) gold is active and mobile in surficial environments; (2) gold occurs not only as discrete grains, but also as ultrafine particles and other complex forms; and (3) regional low-concentration gold anomalies as well as local anomalies over buried gold deposits originate from ultrafine gold and other complex forms of gold. The methodology developed in China for regional and local geochemical gold exploration is based on this experience. Results of investigations around two gold deposits in China are presented.

Включение в традиционную схему отработки золоторудных месторождений процесса подготовки техногенных месторождений формирует принципиально новый подход к решению проблемы рационального использования недр. Данное стратегическое направление позволит существенно укрепить сырьевую базу действующих предприятий и активизировать инвестиции на вовлечение в оборот коренных месторождений золота.

A rapid field method for gold analysis in geochemical exploration has been developed. Cold extraction of Au, at room temperature, using a mixture of sodium bromide, sulphuric acid, hydrogen peroxide is performed; the technique has the advantage of avoiding the irritating odour of commonly used aqua regia digestion. Polyurethane foam is used to concentrate gold from solution. After desorption of Au using mixed reagents (0.5% Na2S03-NaCl solution at pH 8), two sequential procedures, depending on the concentration, are followed for the determination of gold. (1) A 1 mL portion of desorbed solution is used to form Au-TMK-DBS (Thio Micher's Ketone and dodecyl benzene sodium sulphonate) ternary complex. Concentrations below 20 ng/g Au are determined by visual colour comparison of the organic layer with a series of standards. (2) If the concentration is greater than 20 ng/g Au, a complexation reaction using the same reagents is followed by fibre-optic colorimetry. The method is rapid and simple, and the tiresome operation of ashing the foam is avoided. The limit of detection is 0.5 ng/g Au and eighty determinations can be made in one working day. The method could be used for rapid follow-up of rock sample or in situ drill core analyses. About 600 samples from 5 gold districts were tested by this method. The results are very satisfactory.

The Bulletin lode-gold deposit is within the northernmost part of the Norseman-Wiluna greenstone belt in me Archaean Yilgarn Block, Western Australia. It is located within a brittle-ductile shear zone and hosted by tholeiitic metavolcanic rocks. Syn-metamorphic wallrock alteration envelops the gold mineralisation and is pervasive throughout the entire shear zone and extends up to 150 m into the undeformed wallrocks. Alteration is characterised by the sequence of distal chlorite-calcite, intermediate calcite-dolomite, outer proximal sericite and inner proximal dolomite-sericite zones. The thickness of the alteration envelope, and the occurrence of dolomite in the alteration sequence, can be used as a rough guide to the width, extent and grade of gold mineralisation, because a positive correlation exists between these variables. Mass transfer evaluations indicate that chemical changes related to the wallrock alteration are similar in all host rocks: in general, Ag, As, Au, Ba, C02, K, Rb, S, Sb, Те and W are enriched, Na and Y are depleted, and Al, Cr, Cu, Fe, Mg, Mn, Nb, Ni, P, Se, V, Zn and Zr are immobile, while Ca, Si and Sr show only minor or negligible relative changes. The degree of mobility of each component increases with proximity to gold mineralisation. The largest potential exploration targets are possibly defined by regional As (>6 ppm) and Sb (>0.6 ppm) anomalies. These anomalies, if real, extend laterally for > 150 m from the mineralised shear zone into areas of apparently unaltered rocks. Anomalies defined by Те (> 10 ppb), W (>0.6 ppm), carbonation indices, local enrichment of Sb (>2.0 ppm) and As (>28 ppm), and potassic alteration indices also form significant exploration targets extending beyond the HJB shear zone and the Au anomaly (>6 ppb) and, locally, into apparently unaltered rock. Gold, itself, has a restricted dispersion, with an anomaly extending for 1-35 m from ore, and being restricted to within the shear zone itself. Amongst individual geochemical parameters, only As and Sb define significant, consistent and smooth trends (vectors) when laterally approaching the ore. However, the respective dimensions of individual geochenucal anomalies can be used as an extensive, though stepwise, vector towards ore