B.I. Gongalsky, N.A. Krivolutskaya, A.A. Ariskin, G.S. Nikolaev

B.I. Gongalsky, N.A. Krivolutskaya, A.A. Ariskin, G.S. Nikolaev

B.I. Gongalsky, N.A. Krivolutskaya, A.A. Ariskin, G.S. Nikolaev

CHINEYSKY PYROXENITE-GABBRO-ANORTHOSITE LAYERED MASSIF (NORTHERN TRANSBAIKALIA, RUSSIA): ITS STRUCTURE, TI-V AND CU-PGE DEPOSITS, AND PARENTAL MAGMA PARAMETERS

Mineralium Deposita

Bronislav I. Gongalsky

Institute Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS, Staromonetny per., 35, 119017, Moscow, Russia

Nadezhda A. Krivolutskaya

Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, Kosygin Str. 19, 119991, Moscow, Russia

Alexey A. Ariskin

Faculty of Geology, Moscow State University, Leninskie Gory 1, 119991, Moscow, Russia

Vernadsky Institute, Kosygin Str. 19, 119991, Moscow, Russia

Georgy S. Nikolaev

Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, Kosygin Str. 19, 119991, Moscow, Russia

The corresponding author:

Bronislav Gongalsky, Telephone: +7 499 2308265, FAX: +7 495 9511587

e-mail:

Characteristics of ore minerals in the Chineysky Massif

The endo-contact mineralized zone

Two characteristic mineral assemblages have been recognized. The first assemblage consists of chalcopyrite and pyrrhotite occurring in different ratios. The assemblage is characterized by the presence of minor pentlandite as grains and flame-like lamellae occuring along grain boundaries or fractures in the pyrrhotite (Fig. 11b). The typomorphic minerals for this association are cobalt-bearing pyrite, the linnaeite-group (Online Resource 5) of minerals (Krivolutskaya 1986) and sphalerite (Online Resource 6). The second assemblage consists of almost ‘pure’chalcopyrite with arsenides and sulfoarsenides of Co and Ni (Online Resource 7). It is commonly separated in space from high-grade chalcopyrite and pyrrhotite disseminations and makes up an independent mineral assemblage forming pockets and veinlets in monzodiorite and quartz diorite. It is relatively rare and typically contains minerals of the cobaltite–gersdorffite isomorphic series, lellingite, and safflorite. In this type of mineralization, pyrrhotite is almost completely represented by the monoclinic variety. The complex internal structure of the large chalcopyrite grains is caused by development of two types of twins, including single tabular or lenticular twins occurring in small grains.Chalcopyrite commonly contains sphalerite starlets (0.02 mm) or skeletal crystals (0.05 mm). The chemical composition of sphalerite is given in Online Resource 6.

Chalcopyrite is the most abounded mineral; it is represented by tetragonal variety. The grains contains twins forming texture of “oleander leaf”. Pyrrhotite aggregates consist of monoclinic and hexagonal varieties’ intergrowth. These minerals are characterized by constant morphology and composition. Pentlandite and Linnaeite Group minerals are very specific in different types of mineralization, so they are described in details. Pentlandite grains vary in size and morphology (Fig. 11d-f). In the order of their relative abundance these are observed as (i) large (up to 0.3 mm) euhedral grains near the margins of pyrrhotite crystals, (ii) flame-like and lenticular segregations within pyrrhotite, and oval segregations in pyrrhotite. The large pentlandite grains are replaced by violarite, pyrite, and magnetite along the cleavage fractures. Pyrite occurs as outer rims around pyrrhotite grains or as individual thin veinlets 0.2 mm thick, in the host silicate minerals. Linnaeite occurs sporadically and reveals a diversity of morphological forms, varying from lenticular to isometric grains with offsets up to 0.2 mm in size, which are always hosted in pyrrhotite. Siegenite is associated with high-Co pentlandite.

Composition of ore-forming minerals in the Chineysky Massif

The composition of the main ore mineral, chalcopyrite, is relatively constant for different types of sulfide mineralization (see below in the Table 4). Pyrrhotite is the second most widespread mineral in deposits related to the CLM. Variation in its composition equally is not significant, the Fe/S increases from momoclinic to hexagonal pyrrhotite and then to troilite (0.85 -0.92 -1.00). In contrast to chalcopyrite, it contains some Ni (up to 1.75 wt %) and Co (up to 0.26).

Of greatest interest are those minerals that show variation in composition. These include, first of all, pentlandite and the minerals of the linnaeite group. Two varieties can be distinguished among pentlandites: Ni-rich (35-38 wt. %) and Ni-poor (30-33 wt. %). The distinguishing feature of pentlandites from the CLM, is the relatively high content of Co. Different types of sulfide mineralization of pentlandite, namely the cobalt content in it. The cobalt content in pentlandite is stepwise reduced from sulfide mineralization, located in the interior of the massif to endo-contact and then to its exo-contact. The most Co-rich pentlandites (> 18 wt. % Co) were found in titanomagnetite ore of the Etyrko deposit (Type-4 of sulfide mineralization), while pentlandites in endo-contact and exo-contact sulfides (Type 1 and 2-3) have 5-7 and 2-3 % Co, respectively (Online Resource 5). It is important to emphasize, that the Co distribution in pentlandite from different types of sulfide mineralization shows a negative correlation with their economic value. For example, the high-grade ores from out-contact zone of massif comprise pentlandites with the lowest Co contents. This feature can be used for estimation of economic value for other gabbro massifs in the Kodaro-Udokan area.

Minerals of the linnaeite group (linnaeite, siegenite, violarite) were described in all types of sulfide mineralization. Linnaeite-group minerals, especially siegenite, typically forms hexagonal 0.2-0.3 mm size grains, which are hosted mainly by silicate minerals and, less frequently, by chalcopyrite and pentlandite.

The sulfides in titanomagnetite (Etyrko deposit) are dominated by a high cobalt species (Co = 23-31 wt. %), intermediate between linneite and siegenite. In endo-contact ores of the Rydny deposit (1st type of sulfide mineralization) siegenite dominates but in fact, the chemical composition of siegenite and Ni-linnaeite NiCo2S4; it is characterized by significant Fe admixtures (8.04–11.45 wt. %). The composition of violarite substantially differs from the stoichiometric FeNi2S4 due to high Co concentrations, variable proportions of Ni and Fe, and a general shift towards greigite Fe2+Fe3+S4. Exo-contact ores contain the minerals with the lowest Co contents (2-3 wt %) belonging to intermediate member of polydymite-greigite range.

Arsenides and sulfoarsenides were found in endo- and exo-contact ores. As it was mentioned above they form their own association with chalcopyrite in endo-contact sulfide mineralization (the 1st type) in the Rygny deposit. The first group of minerals includes the cobaltite–gersdorffite isomorphic series. Cobaltite is more abundant than gersdorffite and has a composition close to theoretical CoAsS. Gersdorffite crystals (NiAsS) contain Co, Fe, and Cu in addition to the major components. The chemical compositions fall rarely into the field of normal cobaltite and gersdorffite (ESM 7, 9), they are close to transitional compositions, which fit Ni-cobaltite (dzhulukulite) or Co-gersdorffite (Borishanskaya et al. 1981). In out-contact mineralization (Type-3) gersdorffite grains dominate in the isomorphic series. It is characterized by Co admix of 2-3 wt. % while gersdorffite from veins with close to theoretical composition. Thus, one can see the same tendency in variations of cobaltite–gersdorffite isomorphic series as it was established for pentlandite i.e., the Co content decreases from the center of the massif to its endo- and out-contact.

Safflorite and loellingite also occur in related to the mineral assemblage in endo-contact ore. Loellingite pertaining to the Fe–Co diarsenides is enriched in Ni (ESM 7). The second mineral of this assemblage is related to the same Ni-free isomorphic series of Fe–Co diarsenides and approaches safflorite in chemical composition (CoAs2). Among arsenides and sulfoarsenides niccolite and arsenopyrite were diagnosed. They have a chemical composition close to theoretical, niccolite contains sometimes Fe, Co and Cu (ESM 7). In out-contact ores arsenohauchercornite was found. The chemical composition of this mineral is as follows (wt. %): 42.28 Ni, 3.89 Co, 0.48 Cu, 0.77 Fe, 0.09 Ag, 21.31 Bi, 4.95 As, 3.49 Sb, 22.93 S; total is 100.40. The high As content allows us to identify this mineral as arsenohauchercornite (Just, 1980); a rather high Sb content marks its transition to hauchercornite Ni9SbBiS8. These intermediate members of isomorphic series with high As and Sb contents are very rare in nature. The Co content is unusually high for this mineral species. The chemical compositions of bornite, millerite and other minerals show little variation in comparing with their theoretical compositions.

Table ESM 4. Chemical composition of sulfides from the deposits related to the Chineysky Massif, wt. %

No/ / As / S / Fe / Ni / Co / Se / Cu / Total / Deposit
Pyrrhotite
1 / 0.21 / 38.76 / 58.01 / 1.75 / 0.12 / 0.14 / 0.00 / 98.99 / Kontaktovy
2 / 0.17 / 38.76 / 57.79 / 1.62 / 0.15 / 0.10 / 0.00 / 98.59 / "
3 / 0.18 / 38.27 / 58.02 / 1.29 / 0.09 / 0.13 / 0.03 / 98.01 / "
4 / 0.16 / 37.93 / 59.15 / 0.74 / 0.13 / 0.21 / 0.00 / 98.32 / "
5 / 0.27 / 38.25 / 58.83 / 0.72 / 0.26 / 0.18 / 0.00 / 98.52 / Rudny
6 / 0.19 / 38.09 / 58.94 / 0.72 / 0.26 / 0.14 / 0.01 / 98.36 / "
7 / 0.26 / 37.82 / 59.24 / 0.64 / 0.14 / 0.14 / 0.01 / 98.24 / "
8 / 0.13 / 37.67 / 59.85 / 0.62 / 0.24 / 0.11 / 0.01 / 98.63 / "
9 / 0.21 / 37.79 / 59.91 / 0.56 / 0.15 / 0.19 / 0.00 / 97.81 / "
10 / 0.09 / 37.18 / 60.06 / 0.54 / 0.11 / 0.18 / 0.00 / 99.16 / "
11 / 0.20 / 37.36 / 60.15 / 0.44 / 0.10 / 0.15 / 0.00 / 98.41 / "
12 / 0.14 / 37.26 / 60.12 / 0.36 / 0.10 / 0.10 / 0.00 / 98.07 / "
13 / 0.20 / 36.77 / 60.65 / 0.34 / 0.10 / 0.12 / 0.02 / 98.20 / Upper Chineysky
14 / 0.22 / 35.57 / 61.87 / 0.28 / 0.11 / 0.16 / 0.01 / 98.22 / "
15 / 0.19 / 37.36 / 60.82 / 0.25 / 0.10 / 0.20 / 0.00 / 98.92 / "
16 / 0.04 / 39.74 / 59.65 / 0.25 / 0.43 / 0.09 / 0.07 / 100.07 / "
17 / 0.08 / 37.10 / 60.52 / 0.22 / 0.10 / 0.15 / 0.00 / 98.16 / "
18 / 0.17 / 37.09 / 60.90 / 0.20 / 0.10 / 0.16 / 0.02 / 98.63 / "
19 / 0.19 / 37.91 / 60.04 / 0.15 / 0.10 / 0.15 / 0.28 / 98.82 / "
Pyrite
20 / 0.20 / 52.51 / 46.80 / 0.02 / 0.56 / 0.14 / 0.00 / 100.22 / Kontaktovy
21 / 0.17 / 52.79 / 46.83 / 0.01 / 0.36 / 0.13 / 0.00 / 100.29 / "
Cubanite
22 / 0.20 / 35.73 / 41.39 / 0.16 / 0.09 / 0.20 / 21.27 / 99.04 / Upper Chineysky
23 / 0.00 / 33.53 / 40.98 / 0.02 / 0.07 / 0.07 / 22.89 / 97.56 / "
24 / 0.22 / 34.14 / 40.79 / 0.00 / 0.07 / 0.11 / 23.32 / 98.65 / "
25 / 0.15 / 33.76 / 40.62 / 0.03 / 0.07 / 0.19 / 23.42 / 98.23 / Rudny
26 / 0.19 / 31.67 / 38.53 / 0.06 / 0.07 / 0.21 / 24.06 / 70.73 / "
Chalcopyrite
27 / 0.20 / 34.54 / 29.52 / 0.01 / 0.05 / 0.17 / 33.67 / 98.17 / Rudny
28 / 0.21 / 34.13 / 29.75 / 0.45 / 0.05 / 0.19 / 33.78 / 98.56 / "
29 / 0.26 / 34.49 / 30.23 / 0.01 / 0.05 / 0.20 / 33.79 / 99.03 / "
30 / 0.20 / 34.16 / 30.54 / 0.00 / 0.06 / 0.21 / 33.93 / 99.10 / "
31 / 0.18 / 34.39 / 29.70 / 0.03 / 0.06 / 0.17 / 33.95 / 98.48 / "
32 / 0.18 / 33.69 / 30.37 / 0.01 / 0.05 / 0.21 / 34.02 / 98.53 / "
33 / 0.18 / 33.87 / 30.52 / 0.02 / 0.06 / 0.18 / 34.18 / 99.00 / "
34 / 0.17 / 34.35 / 30.09 / 0.01 / 0.06 / 0.26 / 34.20 / 99.04 / "
35 / 0.16 / 33.52 / 30.52 / 0.01 / 0.05 / 0.23 / 34.21 / 98.71 / "
36 / 0.22 / 33.45 / 30.93 / 0.04 / 0.07 / 0.27 / 34.22 / 99.20 / "
37 / 0.22 / 33.45 / 30.93 / 0.04 / 0.07 / 0.27 / 34.22 / 99.20 / "
38 / 0.15 / 34.68 / 30.18 / 0.00 / 0.06 / 0.15 / 34.27 / 99.48 / Skvoznoe
39 / 0.24 / 34.44 / 30.34 / 0.00 / 0.05 / 0.25 / 34.29 / 99.62 / "
40 / 0.14 / 34.63 / 30.50 / 0.01 / 0.05 / 0.26 / 34.29 / 99.88 / "
41 / 0.22 / 34.50 / 30.29 / 0.00 / 0.05 / 0.23 / 34.31 / 99.60 / "
42 / 0.23 / 34.03 / 30.24 / 0.01 / 0.05 / 0.16 / 34.33 / 99.05 / "
43 / 0.23 / 34.11 / 30.13 / 0.00 / 0.05 / 0.23 / 34.35 / 99.09 / Kontaktovy
44 / 0.10 / 34.70 / 30.30 / 0.01 / 0.05 / 0.17 / 34.37 / 99.69 / "
45 / 0.16 / 34.15 / 30.44 / 0.00 / 0.05 / 0.21 / 34.37 / 99.38 / "
46 / 0.20 / 34.11 / 30.45 / 0.02 / 0.06 / 0.24 / 34.38 / 99.45 / "
47 / 0.17 / 34.59 / 30.15 / 0.00 / 0.06 / 0.18 / 34.38 / 99.53 / "
48 / 0.19 / 34.25 / 30.29 / 0.00 / 0.05 / 0.23 / 34.39 / 99.40 / "
49 / 0.15 / 34.49 / 30.25 / 0.00 / 0.05 / 0.22 / 34.39 / 99.54 / "
50 / 0.23 / 34.10 / 30.28 / 0.00 / 0.05 / 0.18 / 34.40 / 99.24 / "
51 / 0.19 / 34.17 / 30.33 / 0.00 / 0.06 / 0.15 / 34.41 / 99.30 / "
52 / 0.13 / 34.47 / 30.28 / 0.01 / 0.06 / 0.20 / 34.45 / 99.59 / "
53 / 0.15 / 33.49 / 30.36 / 0.00 / 0.05 / 0.19 / 34.45 / 98.69 / Upper Chineysky
54 / 0.19 / 34.59 / 30.42 / 0.01 / 0.05 / 0.21 / 34.46 / 99.92 / "
55 / 0.24 / 34.33 / 30.28 / 0.01 / 0.06 / 0.24 / 34.46 / 99.61 / "
56 / 0.23 / 33.31 / 30.40 / 0.00 / 0.05 / 0.13 / 34.46 / 98.58 / "
57 / 0.22 / 33.76 / 30.42 / 0.01 / 0.04 / 0.21 / 34.47 / 99.13 / “
58 / 0.09 / 34.16 / 30.42 / 0.00 / 0.05 / 0.20 / 34.47 / 99.39 / "
59 / 0.15 / 34.10 / 30.42 / 0.00 / 0.05 / 0.29 / 34.51 / 99.53 / "
60 / 0.21 / 34.21 / 30.41 / 0.00 / 0.05 / 0.14 / 34.52 / 99.54 / "
61 / 0.22 / 33.56 / 30.28 / 0.00 / 0.05 / 0.22 / 34.54 / 98.87 / "
62 / 0.17 / 34.43 / 30.36 / 0.01 / 0.05 / 0.24 / 34.57 / 99.83 / "
63 / 0.16 / 33.80 / 30.50 / 0.00 / 0.05 / 0.18 / 34.74 / 99.44 / "
64 / 0.12 / 34.08 / 30.40 / 0.00 / 0.05 / 0.18 / 34.75 / 99.58 / “
Bornite
65 / 25.73 / 11.8 / 0.95 / 0.00 / 62.57 / 101.05 / Rudny. d-60
66 / 25.76 / 12.86 / 0.72 / 0.00 / 59.72 / 99.06 / “
67 / 25.88 / 9.61 / 2.43 / 0.00 / 60.53 / 98.45 / “
68 / 25.88 / 11.33 / 0.26 / 0.00 / 62.82 / 100.29 / “
Millerite
69 / 0.34 / 34.87 / 1.00 / 62.36 / 1.44 / 0.12 / 0.00 / 100.14 / "
70 / 35.34 / 3.56 / 61.65 / 0.26 / 1.14 / 101.95 / "
71 / 35.16 / 2.56 / 61.52 / 0.17 / 0.23 / 99.64 / "
72 / 34.85 / 0.87 / 61.16 / 0.78 / 100.18 / Rudny. d.h.20/133
73 / 35.37 / 0.76 / 62.44 / 0.6 / 99.17 / Rudny.d.h.20/138
74 / 35.35 / 0.75 / 63.14 / 0.52 / 0.18 / 99.95 / "
75 / 34.78 / 0.72 / 63.17 / 0.5 / 99.17 / "
76 / 33.79 / 0.83 / 63.26 / 0.63 / 0.17 / 98.68 / "
77 / 35.24 / 1.05 / 63.69 / 0.72 / 100.69 / "
78 / 35.98 / 1.00 / 60.84 / 1.34 / 99.16 / Rudny. L-2
79 / 34.87 / 1.00 / 62.36 / 1.44 / 0.12 / 0.00 / 100.14 / Rudny. L-2

Note. d.h. is drill hole 20; L-2 is lense 2; d - 60 is ditch 60; here in Tables 5-7 analyses carried out by EPMA (CAMECA SX 100) at Vernadsky Institute of Geochemistry and Analytical Chemistry RAS, analyst N. Kononkova.